Should Climbers do Blood Flow Restriction (BFR) Training? | Research Review
Hooper’s Beta Ep. 106
INTRO
How do you train or prevent strength loss when you’re injured? How do you gain strength while also being able to put in quality sessions on your project?
The answers to those questions often depend on who you ask. But there’s one technique that some say is the solution to all three, even though it might not sound very enticing, and that is: blood flow restriction (BFR).
BFR training has actually been around for quite a while, with research going back to the 90s as a potential rehab and training tool. And I’ve seen it discussed in climbing circles somewhat recently, probably for good reason: some advocates claim it’s superior to traditional resistance training.
But is that actually true? To find out, we’re going to have to assess the following:
As always, we’ll look to science for answers.
WHY THE HYPE?
First, let’s understand why BFR has been getting more hype.
Take a look at my right arm; I curled this 25 lb weight for about 10 reps and my arm is starting to feel pretty tired. Now look at my left arm; I curled this 10 lb weight for the same number of reps and don’t feel much fatigue at all. Rep for rep, the 25 lb weight is obviously making my arm work harder, which, in a simplified sense, should lead to greater adaptations.
Now, if I rest a few minutes, then use a BFR band (this one’s from SAGA) to restrict some of the blood flow in my left arm, let's see what happens when I repeat the reps.
Of course, my right arm feels fatigued again -- no surprise there. But now my left arm feels quite fatigued also! It kind of feels like I’m getting a similar workout with the 10 lb weight as I am with the 25 lb weight. Could I be getting the same benefits with light loads as I would with heavy loads?
If so, that could solve a lot of our problems:
We could prevent strength loss by training with light-loads and not disrupt the healing process
We could keep training hard without aggravating an injury or tendinopathy
We could strength train AND put in quality sessions on our project
We could avoid the inconvenience and potential hazards of training with heavy loads
We could potentially add BFR to our regular training to get even more gains!
And that’s just the start! Sound too good to be true? Let’s find out.
THE RESEARCH
Remember that not all research is created equal. To obtain relevant results, you need to meet certain criteria:
Large, representative sample sizes
Randomized assignment
Double-blinded (not possible with BFR studies)
Valid objective measurements
Appropriate study duration (not too short!)
Significant effect size
Note that, as one systematic review claims, “it is not possible to blind athletes” [III] to whether they are training with BFR or not -- they will obviously know when they have a cuff on their limb. That could cause them to change their behavior. For example, they could try harder than normal, or be uncomfortable and not try as hard. As a result, the participants and consequently the results may be more prone to bias in BFR studies.
Finally, remember there are different types of research. Systematic reviews are typically at the top of the pyramid, with randomized, controlled trials just below that and things like case studies and expert opinion at a much higher risk of bias and generally lower quality of evidence. There should be one giant asterisk next to systematic reviews, however, and that is: they are only the gold standard if the articles they review are themselves high quality, and unfortunately that is not always the case.
[Yetley]
So let’s keep our eyes peeled for tomfoolery and see if we can answer our main question:
Does BFR actually work?
Overview: This 2017 review included 33 studies from 1990 to 2016. Their goal was to compare the effectiveness of low-load BFR (LL-BFR) training with low-load (LL) and heavy-load (HL) non-BFR training. They also sought to recommend safe and effective implementation of BFR training.
Result: N/A - No specific results regarding efficacy or changes with BFR. Discussed later in Conclusions.
Researcher’s Conclusion: LL-BFR training is more effective at improving strength in injured muscle tissue than LL training without BFR. LL-BFR training is less effective than HL training (non-BFR) but is better tolerated. LL-BFR could be an effective training strategy or surrogate for HL training. No safety concerns. High occlusion percentages are not necessary. 2-3 sessions of BFR training per week is sufficient.
My Take: Some of the information is a bit old, going back a few decades, but the study itself looks pretty solid. Briefly reviewing the articles they chose to include, there are lots of long, 10-12 week studies with significant changes reported. The only small catch being that the population in many of the studies is an elderly population which may not translate perfectly to a young, athletic population. But the fact that BFR training appears to be safe (even for the elderly!) and that high occlusion amounts are not necessary are big pros for me, and 2-3 sessions per week is doable for most people. The fact that LL-BFR training was more effective than LL training by itself but less effective than HL training helps to carve out BFR's role in early rehab. It appears to be an effective means of transitioning back into heavy loads further down the road.
Verdict: This is one check in favor of BFR training for muscle rehab.
What if you’re not injured? Is BFR training effective in healthy athletes?
ARTICLE II: Blood Flow Restriction Training for Athletes: A Systematic Review
Overview: This 2020 article reviewed 10 studies with a total of 250 athletes (no climbers, unfortunately). They sought to assess the usefulness of BFR training as a supplement to traditional resistance training in healthy athletes.
Results: 7 out of 9 studies found an increase in strength, 4 out of 8 found increases in muscle size, and 3 out of 4 reported improvements in sport-specific measurements in groups that used BFR compared to controls.
Researcher’s Conclusion: BFR training has the potential to increase strength, muscle size, and sport-specific performance metrics when done as part of a regular resistance training program.
My Take: While it’s neat that they found mostly positive results, let’s dig a bit deeper. In the 10 total studies they included, the study duration ranged from 8 days to 8 weeks. 8 days?! Okay, now my skepticism alarm is raised. If you just read the abstract, you’d think that this paper is a major win. But when you dig deeper, you get conflicting results. One 5 week study found no difference between BFR and the control. Another 4 week study did find improvements, including improvements in bench press… Only to be followed up by another study that did NOT notice improvements in bench press. Personally, my head is spinning.
Verdict: At most what I would take away from this is that BFR has the potential to work in healthy athletes and does not appear to be worse than traditional HL training, but that there are still conflicting results. Let’s see if we can find some more definitive evidence.
ARTICLE III: Blood flow restricted exercise for athletes: A review of available evidence
Overview: This 2015 systematic review includes 12 different papers. They sought to determine the efficacy of BFR training in well-trained athletes. 8 of the 12 articles they included overlap with the previous systematic review. So… they swapped in a few new articles! Let’s see how their results and conclusions compare by changing those studies.
Results: Most studies showed hypertrophic and/or strength benefits to BFR training methods.
Researcher’s Conclusion: Evidence points to LL-BFR training enhancing muscle hypertrophy and strength in well-trained athletes who would not normally benefit from such light loads. LL-BFR training in conjunction with high-load training may provide additional stimulus for muscular development. Adaptations may not be equal in tendons, which could lead to an increased risk of subsequent tendon injuries.
My Take: They state a more definitive conclusion with more evidence pointing to the potential benefit of combining LL-BFR with traditional HL resistance training, which is enticing. In fact, in one study (that was included in the previous SR as well) participants who supplemented their training with BFR saw a 24kg improvement in their squat compared to only 14kg of improvement in the non-BFR group. However, the other 4 articles that they swapped in were not good. Their findings were unconvincing, and one of the articles only studied a single subject with one session of BFR.
As for their concern about the tendon adaptations, that is alarming, especially for climbers. While they don’t seem to be basing that concern on experimental evidence, I think it’s worth looking into further. But my skepticism is definitely raised.
Verdict: While the authors deemed the articles credible enough to base somewhat definitive conclusions on, I personally wouldn’t call this review particularly convincing.
Aside from a couple good articles, the evidence for strength and hypertrophy BFR training in healthy athletes seems unclear, so for now we’ll have to move on.
Does BFR training introduce greater risk of tendon injury?
Overview: This fresh, 2021 study focusing on the patellar tendon is quite similar to the last article: 29 active male participants split into three groups, training 3 times a week over the course of 14 weeks. But there was one major difference: they used ultrasound and MRI. Bingo!
Results: Comparable changes in tendon stiffness, cross sectional area, muscle mass, and muscle strength between LL-BFR and HL groups.
Researcher’s Conclusion: Both LL-BFR and HL training cause similar and substantial changes in patellar tendon properties, though the mechanism behind this needs further research.
My Take: This is huge! Though the sample size was smaller, the use of MRI makes their results much more conclusive in my opinion. Of course, for climbers, I would prefer to have data on the finger flexors over the patellar tendon, as we can’t say for sure that we’d get the same results.
Verdict: Considering this is the best evidence we have to go on at the moment, I think LL-BFR training appears to be safe for climbers -- though research specifically on the finger flexors is needed.
WHAT THE RESEARCH TELLS US
And that’s it for the most relevant articles on BFR. Let’s see if we can answer our original questions:
Is the research good? The quality is somewhat mixed.
Is BFR effective for rehab? It appears so, especially when HL is not tolerated.
Is BFR effective for strength and hypertrophy training? Not enough quality research to make a confident determination. BFR’s superiority is mostly unsupported, though it does not appear to yield worse results than traditional HL training. Combining LL-BFR with traditional HL looks promising.
Are there any safety concerns? It appears not, but more climber-specific data would be nice.
Why does BFR seem to work? From our discussion with Dr. Brummit, the mechanisms at play in BFR seem relatively clear; many are the same as traditional HL training -- things like increased fiber recruitment and hormonal responses. However, there are other processes at play as well that could explain BFR’s effectiveness, such as the low oxygen environment and cellular swelling it creates. Overall, it is not clear how significant of a role each of these mechanisms play.
Is it worthwhile for climbers? For rehab, it appears so. For regular training, it’s unclear, though there don’t appear to be any significant downsides. It should be noted, however, that BFR training requires occlusion of a limb to work, and much of the training climbers do is back- and shoulder-focused -- which you obviously can’t directly occlude. This doesn’t mean BFR won’t have any effect, though. One study showed better gains in bicep training when occluding the legs. But other studies on “indirect” BFR do not support this, so the data is currently mixed.
Meanwhile, there actually is a fair amount of BFR research that more directly involves climbing, but… we’re not going to analyze it in-depth in this video. Sounds like an odd choice, but it’s because it either doesn't provide relevant information to this video, doesn’t lead us to any new conclusions, or doesn't meet the standards of quality we laid out earlier in the video (or I couldn’t read it -- if anyone knows Persian, please enlighten us!
MY RECOMMENDATIONS
From a rehab perspective, I think LL-BFR can provide an enhanced healing environment by getting some of the effects of HL training without the risk. Can I say this with 100% certainty? No, because there isn’t much quality data on climbers using BFR for rehab. But with such low risk, I’m giving it a strong recommendation.
From a performance or training perspective, I think LL-BFR could be helpful if combined with regular HL training, but I currently don’t see a reason to do only BFR training. Because the risk appears low, there aren’t any compelling reasons not to try it if you’re interested and capable. I’ll need to see more data and especially more climber-specific research before I can really get behind it, though. Because of that, I’m giving BFR a solid recommendation.
HOW TO TRY OUT BFR FOR YOURSELF
If you do want to try BFR, here are some general guidelines to get you started:y
First, don’t use any old band or strap: buy a set of legit cuffs from a company like SAGA or B strong.
Second, understand appropriate training protocols, based on current available evidence:
Third, be aware that while most research shows low risk of adverse effects, that conclusion is derived from studies performed under trained supervision. There are also several contraindications for BFR which I’ve listed below. Talk to a physician before trying BFR if you have any medical issues.
Fourth and finally, don’t drastically spike your training by supplementing it with BFR. Take a gradual approach to implement it into your routine and monitor for any negative effects this may be having on your other training.
CONCLUSION
And that's it for this episode!
Until next time…
Train with BFR until you can climb with the swollest of swoll arms and send your project while flexing your veins out at all your buddies and repeat but this time with the cuffs off because you actually didn’t send because you were far too pumped, oh and because you definitely spent way too much time admiring all of your veins and forgot to climb.
RESEARCH
Title
Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis
Citation
Hughes L, Paton B, Rosenblatt B, Gissane C, Patterson SD. Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis. Br J Sports Med. 2017 Jul;51(13):1003-1011. doi: 10.1136/bjsports-2016-097071. Epub 2017 Mar 4. PMID: 28259850.
Key Notes
Introduction
Historically, heavy exercise loads of approximately 70% of an individual’s one repetition maximum (1RM) have been deemed necessary to elicit muscle hypertrophy and strength gains
Recent research has demonstrated that low-load training to failure can stimulate muscle hypertrophy comparable in magnitude to that observed with heavy-load training after and weeks of training three times per week
However, strength adaptations were maximised with heavy-load training
And cross-sectional comparisons would suggest that hypertrophy and strength gains observed with low-load training are not as great as those achieved with heavy-load training.
Training with low loads may therefore be useful, as the early addition of muscle mass and function in rehabilitation may be beneficial for individuals who have suffered from atrophy.
In recent years, research has demonstrated that augmentation of low-load resistance training with blood flow restriction (LL-BFR) to the active musculature can produce significant hypertrophy and strength gains,
BFR training has been found to yield hypertrophy responses comparable to that observed with heavy-load resistance training; however, studies with such findings regarding muscle hypertrophy are not common among the present literature.
From a mechanistic standpoint, it is hypothesised that an ischaemic and hypoxic muscular environment is generated during BFR to cause high levels of metabolic stress, alongside mechanical tension when BFR is used in tandem with exercise. Both metabolic stress and mechanical tension have been described as ‘primary hypertrophy factors and theorised to activate other mechanisms for the induction of muscle growth
These proposed mechanisms include: elevated systemic hormone production cell swelling production of reactive oxygen species (ROS), intramuscular anabolic/anticatabolic signaling and increased fast-twitch fibre recruitment
However, at present these are mainly hypothetical and theoretical-based associations
Pragmatic and specific identification of these proposed mechanisms, including their magnitude of involvement and actual source of activation in BFR-induced hypertrophy is currently lacking and requires further exploration.
The objectives of this review were to
(1) compare the effectiveness of LL-BFR training to both low- and heavy-load training without BFR;
(2) systematically review studies examining LL-BFR training in clinical MSK rehabilitation and
(3) from the results of the systematic analysis, examine and provide recommendations regarding safe and effective implementation of BFR training in clinical musculoskeletal rehabilitation.
Methods
Timeframe of search: 1990 to 2016
1502 articles initially found, 171 were assess for eligibility
33 total studies were pulled from there
Discussion
The results indicate that augmentation of low-load rehabilitative training with BFR can produce greater responses in muscular strength compared with low-load training alone
Thus, LL-BFR training may be used as a progressive clinical rehabilitation tool in the process of return to heavy-load exercise
It is important to note that this review indicated the strength gains observed with LL-BFR training were smaller in magnitude than those observed with heavy-load training.
a large majority of studies do not report on any or no adverse events to BFR
may even be used without exercise to prevent muscle atrophy in early immobilization.
BFR training has been reviewed in depth and correct implementation has been affirmed to present no greater risk than traditional exercise modes.
At present, there are no complete standardized recommendations for use even in healthy populations.
Although muscle damage is common in BFR exercise and is necessary for training effects/adaptations, the possible risks of rhabdomyolysis occurring during BFR exercise may be heightened in cases of muscular disuse atrophy
Recent research employing this technique during BFR exercise demonstrated that higher LOP pressures are not required for greater facilitation of muscular responses to exercise compared with lower pressures. Furthermore, 40% LOP produced similar increases in muscle size, strength and endurance after 8 weeks of training to that of 90% LOP but without the high ratings of discomfort that were reported with the latter pressure.
Lower and more tolerable pressures may elicit sufficient MSK adaptations while minimizing the risk of adverse events and pain, highlighting the need for individualized prescription of clinical BFR training.
Although pronounced hypertrophy and strength weeks gains have been reported after 4 weeks, 2 and even only 6 of LL-BFR training, conflicting research demonstrated that BFR did not accelerate strength adaptations following 4 weeks of low-load training suggesting longer training durations may be necessary
Progression of training load by re-evaluation of training prescription tools such as the 1RM is necessary for continued MSK adaptations to occur.
Two to three LL-BFR training sessions per week with progressive overload is sufficient for enhanced strength adaptations.
In older adults who are increasingly susceptible to sarcopenia, LL-BFR training was shown to stimulate mTORC1 signalling and muscle protein synthesis in older men
An interesting observation in this systematic review is that the addition of BFR to low-load strength training does not appear to worsen condition or exercise-related pain.
The authors actually observed less knee pain during exercise across the training period in the LL-BFR group, likely attributable to the lower exercise load, alongside similar increases in muscle size and strength to the heavy-load group.
Conclusion
The clinical relevance of this review is the demonstration that LL-BFR training can provide a more effective approach to low-load and more tolerable approach to heavy-load rehabilitation.
Title
Blood Flow Restriction Training for Athletes: A Systematic Review
Citation
Wortman RJ, Brown SM, Savage-Elliott I, Finley ZJ, Mulcahey MK. Blood Flow Restriction Training for Athletes: A Systematic Review. Am J Sports Med. 2021 Jun;49(7):1938-1944. doi: 10.1177/0363546520964454. Epub 2020 Nov 16. PMID: 33196300.
Key Notes
Introduction
This technique is believed to have originated in the 1970s with Dr Yoshiaki Soto’s Kaatsu resistance training; however, it was not until 1998 that the first study was published on BFR training
It has been suggested that with the use of BFR, resistance training at 20% to 50% 1RM can result in muscle hypertrophy similar to that of traditional strength training protocols
It remains unclear how BFR elicits cellular responses to increase recovery and promote muscle hypertrophy
Several hypotheses have been proposed, including that the cellular mechanism is related to metabolic stress elevated muscle fiber recruitment, or other metabolic signaling mechanisms leading to increased muscle development through the enhanced production of growth hormone or the accumulation of metabolites, causing muscle cell swelling.
The purpose of this systematic review was to analyze the available literature regarding the use of BFR to supplement resistance training in healthy athletes.
Methods
10 studies were used for this review
total of 250 athletes (220 male, 30 female)
various sports, including track and field, rugby, American football, weightlifting, netball, jiu-jitsu fighting, and soccer
The participating athletes ranged in age from 19.8 to 25.9 years.
Study length ranged from 8 days to 8 weeks
Frequency of sessions from 1 per day to 4 sessions per week
Varying intensities of training, ranging from 20% 1RM to 80% 1RM
Three categories measuring sports performance outcomes were examined in this study: strength improvements, sport-specific markers for performance, and changes in muscle size
strength was assessed via isotonic 1RM tests for the squat and bench press
7 of 9 reported significant improvements in strength
2 of 9 reported no difference between BFR and control
Sport performance
4 total reports
3 of 4 showed significant improvements
1 of 4 showed no difference bweetn BFR and control
Muscle size
8 total reports
4 showed significant improvement
4 showed no difference between BFR and control groups
Ultimately doesn’t seem like we can say much about muscle size and BFR, the studies weren’t great
Studies that measured markers of sports performance utilized the following tests: sprint testing, countermovement jump power,muscular endurance, agility test, vertical jump test, and 20-m shuttle run test.
Three of 4 (75%; n = 65/86) studies demonstrated a significant improvement (P.05) in the groups that used BFR training for at least 1 of these 6 metrics
Scott et al reported no significant improvements among male semiprofessional soccer players in countermovement jumps or sprint performance in a 5-week traditional resistance training regimen with added BFR workouts
Discussion
BFR has various uses, including incorporation into training regimens for high-level athletes or postoperative rehabilitation for patients with limited activity and weight-bearing. Given the ability of BFR to stimulate gains at a submaximal load, athletes can incorporate this treatment at the end of a workout to achieve more muscle development. Additionally, BFR training could be used in athletes who are susceptible to injuries or who cannot tolerate the traditional sets and repetitions of 60% to 75% 1RM.
This systematic review demonstrated that BFR training could lead to significant improvements in muscle strength, markers of sports performance, and muscle size.
Presently, there is substantial variability with regard to the proposed frequency and durations of BFR training.
Additionally, variations exist among the protocols for this type of training with regard to cuff size, cuff pressure, and frequency of training, which can lead to differing results among athletes. This makes it challenging to draw conclusions regarding which sports and athletes can most benefit from BFR training.
Scott et a (n = 228) concluded that muscular development is possible in well-trained athletes after low load resistance BFR training but the neural stimulus is different as compared with traditional high-load regimens.
In 2018, Lixandrao et al performed a systematic review to examine the effects of BFR training in a population that included a broad spectrum of ages and with low-load resistance as compared with high-load resistance training. The authors found that there were greater muscle strength gains in the group using high-load exercise over BFR training.
Hughes et a concluded that Low-load BFR Training could Provide a More effective approach to low-load resistance training in a broad population undergoing clinical musculoskeletal rehabilitation.
The studies included in our systematic review demonstrated mixed results in terms of whether BFR can be used alone or in combination with regularly scheduled training programs.
Scott et al found that 5 weeks of traditional resistance training combined with BFR versus resistance training alone led to no difference in strength, muscle size, and sports performance testing results in 21 semiprofessional soccer players.
Conversely, Yamanaka et al found a significant improvement in 1RM of bench press and squat in 32 Division I football players using BFR training in comparison with a control group undergoing normal training over the course of 4 weeks
Luebbers et al also evaluated the use of BFR in football players and found a significant increase in 1RM of squat but not bench press. The study also found no significant difference in muscle size changes.
Thus far, BFR training has been shown to be relatively safe, with very few complications reported and no apparent increased risk for clotting. Iversen and Rosta reported 1 case of ischemic exercise–induced rhabdomyolysis, although this is the only known report.
Limitations
First, there is substantial variability with the implementation of BFR training.
The training protocols in the studies varied drastically in their frequency, duration, and exercise regimens. This makes comparing results challenging in that athletes respond differently when they undergo different-style workouts.
Second, only 10 studies met our inclusion criteria.
Third, it is not possible to blind athletes in terms of whether they are training with or without BFR.
This could affect the results, as the athletes may have worked harder in the BFR group, given the novel nature of the training.
Fourth, the cuff pressure during training varied considerably among the BFR protocols identified.
Conclusions
This systematic review demonstrated that BFR training has the potential to increase strength and performance when incorporated as part of resistance workout regimen for healthy athletes.
Future studies should also seek to define the ideal duration and frequency of training, number of repetitions, and cuff pressure needed to obtain the greatest benefit from BFR.
Title
Blood flow restricted exercise for athletes: A review of available evidence
Citation
Scott BR, Loenneke JP, Slattery KM, Dascombe BJ. Blood flow restricted exercise for athletes: A review of available evidence. J Sci Med Sport. 2016 May;19(5):360-7. doi: 10.1016/j.jsams.2015.04.014. Epub 2015 May 9. PMID: 26118847.
Key Notes
Introduction
Traditional guidelines state that for substantial increases in muscle size and strength, resistance training should be performed using at least 70% of the concentric 1-repetition maximum (1RM).
However, increasing evidence supports the use of low-load resistance exercise combined with moderate blood flow restriction (BFR) to facilitate hypertrophic and strength gains
the aim of maintaining arterial inflow while occluding venous return during exercise
While current research agrees that this strategy can promote improvements in muscular size and strength, the definitive mechanisms underpinning these responses have not been fully elucidated.
The primary mechanisms, increased proposed include increased metabolic stress increased muscle fiber recruitment, cellular swelling, enhanced intramuscular signaling for protein synthesis, and proliferation of myogenic stem cells, all of which are thought to promote muscular development.
An important benefit of BFR resistance exercise is that relatively light loads can be used to facilitate hypertrophic responses similar to traditional high-load unrestricted resistance training
BFR Training Responses in Athletes
An interesting finding was from Manimmanakorn et al. that these enhanced muscular responses translated into improved performance in sport-specific fitness tests including 5 m sprint, 505 agility, and 20 m shuttle run tests. However, it is unclear whether similar improvements could have been observed if the athletes underwent a traditional resistance training program using heavier loads.
split program in one of four groups; (1) traditional high-load training, (2) traditional high-load training supplemented with low-load training, (3) traditional high-load training supplemented with low-load BFR training and (4) modified traditional training (excluding high-load bench press and squatting variations) with low-load BFR trainin
Results indicated that the group performing high-load training supplemented with low-load BFR training demonstrated the largest increases in squat 1RM
Interestingly, the group performing modified normal training with supplemental BFR exercise demonstrated the smallest increases in both bench press and squat 1RM.
As all other groups in this study performed high-load exercise during their normal training, these data indicate that high-load strength training is paramount for maximal strength development in athletes.
Similar results have been reported in recreationally active young men, with participants who underwent high-load unrestricted training or combined low-load BFR and unrestricted high-load training demonstrating increases in maximal isometric elbow extension. However, a group who trained only with low-load BFR exercise did not demonstrate significant improvements in maximum isometric strength
It should also be acknowledged that these results might reflect the specificity of training to the strength testing procedures; it is to be expected that participants who trained with heavy loads will perform better during maximal strength tests than those who trained exclusively with low- and moderate-loads
These collective findings have important implications for the strength and conditioning coach. While some athletes can achieve significantly enhanced muscular size following brief periods low-load BFR resistance training of athletes with extensive strength training experience, may not be able to achieve the same level of hypertrophy, even with the addition of traditional high-load strength training.
For highly-experienced athletes, using low-load BFR exercise as a supplemental stimulus following normal high-load training can enhance the adaptive strength responses.
From the limited data available, it is evident that the training experience of the athlete must be considered when determining how best to incorporate BFR exercise into their training plan, as not all athletes will respond similarly.
Abe et al demonstrated that collegiate track and field athletes can benefit from brief periods of high-frequency training using low-load BFR exercise. Subjects trained twice daily for 8 consecutive days using squat and leg flexion exercises with BFR (3x15 repetitions at 20% 1RM with 30 s inter-set rest). While a training period this short would not normally facilitate significant muscular gains in athletes, increases were observed in thigh muscle thick-ess (measured via ultrasound) and leg press 1RM following the training program.
Furthermore, 10 m acceleration and 30 m sprint times were significantly improved following BFR training, suggesting that adaptations to low-load BFR training translate to enhanced sport-specific performance in athletes
Low-load BFR resistance and exercise does not appear to cause muscle damage due to the low mechanical loads used, is not likely to excessively stress connective tissues.
However, it is important to consider that while the low mechanical forces used with BFR exercise may improve muscle strength, disproportionate adaptations could occur in the tendons if progressions in exercise load are not implemented, increasing the risk for subsequent tendon injuries.
Cook et al examined rugby union players performing squat, pull-up and bench press training (5 sets of 5 repetitions with 70% 1RM) either with or without BFR applied to the lower limbs (180 mmHg). The BFR training condition resulted in significantly greater improvements in 1RM for the bench press (5.4± 2.6 kg) and squat (7.8 ± 2.1 kg), compared to the control con- dition (3.3 ± 1.4 and 4.3 ± 1.4 kg, respectively).
The results of Cook contradict those of Laurentino et al who have previously demonstrated no additional benefit for BFR during moderate-load (12RM) and high-load (6RM) resistance exercise on measures of muscular strength and size.
These contrasting findings may be related to methodological differences. For example, subjects in the trained study of Cook et al. 3 times per week using 5 sets of three different exercises for 3 weeks, whereas those in the study of trained Laurentino et al twice weekly using 3–5 sets of a single exercise for 8 weeks.
Important to note from this that it may be the methods of HOW BFR training is done that makes a difference, and that is what truly has a huge range and large discrepancies currently
This may have allowed for greater clearance of metabolic by-products between sets, especially considering that both investigations used intermittent BFR (pressure released between sets), which could have caused different degrees of metabolic stress between the studies. Increased metabolic stress is thought to be a primary moderator of adaptation to BFR exercise.
some research has not found low-work rate cardiovascular training with BFR to facilitate increased aerobic adaptations, even for older adults.
Further evi dence is therefore needed before sound recommendations can be made as to the use of low-work rate cardiovascular BFR exercise for enhanced aerobic adaptations in athletes.
Acute Responses to BFR Exercise in Athletes
Takarada et al. demonstrated that bilateral knee extension exercise (5 sets to failure at 20% 1RM with 30 s inter-set rest) performed with BFR (214 ± 8 mmHg) resulted in significantly greater blood lactate and growth hormone concentrations than a work-matched unrestricted control condition.
Notably, growth hormone concentrations following the BFR exercise were ~290 times greater than baseline.
Furthermore, markers of muscle damage (creatine kinase) and oxidative damage (lipid peroxide) were not different between conditions.
These results were among the first to provide evidence of the anabolic potential of the BFR stimulus, although the role of acute elevations in growth hormone in skeletal muscle protein synthesis has recently been questioned.
Takada et al examined the acute metabolic responses to low-load BFR exercise in endurance and sprint athletes.
Results indicated that metabolic stress, estimated via decreases in phosphocreatine and intramuscular pH levels, was significantly greater in endurance runners compared with sprinters. It is possible that the endurance runners are more dependent on oxygen delivery during exercise, and therefore suffered a greater disturbance in energetic metabolism during BFR exercise
Similarly, as sprint athletes are generally more accustomed to performing under conditions where oxygen availability does not match demand, they may not be as metabolically challenged by the addition of BFR to low-load resistance exercise as endurance athletes.
Practical Applications of BFR training for Athletes
implementing BFR during various phases of an athlete’s periodised training plan could help counter the potential negative effects of high mechanical training loads.
while BFR training seems to provide a physiological stimulus for muscular adaptations, the low-loads used do not cause measurable muscle damage
This strategy may therefore be useful for athletes with a decreased capacity for recovery from high-load exercise
an application of BFR for athletes may be decreasing the time required to recover from an injury.
A survey of 105 training facilities in Japan has previously reported that rhabdomyolysis occurred following BFR training in only 0.008% of participants.
It should also be acknowledged that low-load BFR resistance exercise produces lower levels of muscle recruitment than high- load exercise without BFR.
Therefore, the neurological stimulus resulting from BFR training would not likely benefit athletes in sports where rapid force production is required.
Considering these results, BFR training should not be used as a sole means of muscular development in athletes. It is likely that optimal muscular adaptation will result from a combination of traditional resistance training and BFR methods.
It has also been hypothesized that while low-load resistance exercise with BFR can increase the strength and CSA of skeletal muscle, concomitant increases in the strength of connective tissues may not occur due to decreased mechanical loading
A disproportionate increase in muscle and connective tissues strength may result in musculotendinous injury, particularly if heavy loads are subsequently used which can be lifted by the muscles but not tolerated by connective tissues
Summary
Evidence suggests that significant muscular development is possible in well-trained athletes following low-load resistance training with BFR.
However, low-load BFR exercise provides a dissimilar neural stimulus compared to high-load resistance exercise.
For athletes with extensive strength training experience, optimal muscular adaptations may require traditional high-load resistance training in combination with low-load BFR training.
A useful strategy to combine these two training methods is using low-load BFR exercise as supplemental exercise following a high-load strength training session
Studies have also noted that the adaptive responses to BFR training translate to improved performance in sport-specific fitness tests, though physiological responses may differ between different types of athletes.
Title
Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training
Citation
Centner C, Lauber B, Seynnes OR, Jerger S, Sohnius T, Gollhofer A, König D. Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training. J Appl Physiol (1985). 2019 Dec 1;127(6):1660-1667. doi: 10.1152/japplphysiol.00602.2019. Epub 2019 Nov 14. PMID: 31725362.
Key Notes
Introduction
For promoting increases in muscle mass and strength, it has generally been recommended to apply training loads of 70– 85% of each individual’s one-repetition maximum
Evidence from a recent meta-analysis (11) indicates that also in this context training loads 70% of the 1RM are superior in promoting optimal adaptive responses in mechanical (stiffness) and material (Young’s modulus) tendon properties compared with low-load (LL) training.
However, it is largely unknown to what extent training with BFR facilitates changes in human tendon properties.
Accordingly, the main purpose of the present study was to investigate the effects of LL-BFR training (20–35% 1RM) on in vivo tendon properties and compare these effects with conventional HL (70–85% 1RM) resistance training.
it is necessary to investigate tendon adaptive responses to this regimen since adaptations at the muscular level without concomitant changes of tendon properties might lead to increased risks of myotendinous injuries
Methods
a total of 55 healthy men between the age of 18 and 40 yr were recruited.
All subjects were untrained
maximum of 1–2 h of physical activity per week.
Participants diagnosed with acute or chronic injuries of the Achilles tendon, uncontrolled hypertension, or any other chronic disease were excluded from the trial.
HL resistance training (70–85% 1RM), LL (20–35% 1RM) resistance training with BFR (LL-BFR), and a control (CON) group without any training.
Achilles tendon properties and unilateral maximal plantar flexion torque were determined.
14 week intervention period
3 weekly sessions
four sets with 30 repetitions in the first set and 15 repetitions in the remaining three sets were completed
This protocol was chosen because this has been frequently applied in the BFR literature
cuff pressure was set to 50%
kept inflated during the entire session including the 60-s interset rest periods.
Results
A total of 38 participants successfully completed the study
Continue
Discussion
To the best of our knowledge, this is the first study that evaluated the effects of LL-BFR training on functional and structural Achilles tendon properties.
The overall finding revealed that, despite a much smaller training load, LL-BFR caused adaptions in Achilles tendon CSA and mechanical properties as well as in muscle mass and strength comparable to HL.
LL-BFR and HL training serves as a potent stimulus for causing tendon hypertrophy compared with a nonexercising control group.
several studies show that structural adaptations can also be detected as early as 9–12 wk after heavy-load resistance training
The observed increases in Achilles tendon CSA in the present study in the HL group (4.6%) greatly mirrored results from earlier investigations reporting changes in tendon CSA between ~4% and 7% following several weeks of exercise training (5, 33, 52).
Interestingly, not only the HL but also the LL-BFR group displayed a significant increase in Achilles tendon CSA (7.8%) with training loads well below those that have been used previously
The study of Kubo and colleagues (35) revealed that LL-BFR (20% 1RM) and HL (80% 1RM) training for the knee extensors failed to elicit substantial patellar tendon hypertrophy after 12 wk of resistance training.
Potential reasons for this inconsistency might lie within the methodological approach. In their study, Kubo et al. (35) used an average of three tendon CSA values (25%, 50%, and 75% of tendon length) to assess tendon hypertrophy even though it was shown that exercise-induced changes in tendon CSA primarily occur at the proximal and distal sites of the tendon
Although our results indicate that LL-BFR and HL training are equally effective in facilitating tendon hypertrophy, our study design does not allow us to answer the question of the extent to which the hypoxic condition itself contributed to the increased tendon CSA
Besides the morphological changes, the results of the present study show that Achilles tendon stiffness was substantially improved after HL (40.7%) and LL-BFR (36.1%) training, with no changes in the CON group (3.6%).
At first sight, the increased stiffness following LL-BFR training with loads of only 20–35% 1RM seems surprising given that a previous meta-analysis indicates that training loads of 70% MVC are needed to induce adaptations in tendon stiffness
Studies comparing long-term HL and LL-BFR training state that the muscle activation level (assessed with superimposed electrical stimuli) significantly increased after 12 wk of heavy-load training (3%), with no changes in LL-BFR
Limitations
The present study design did not allow us to answer the question to what extent the BFR stimulus alone might be responsible for the muscular and tendinous adaptations because we did not include a group that trained with loads similar to the LL-BFR group but without vascular occlusion
Furthermore, the US-based assessment of tendon CSA has been reported to lack sensitivity and high accuracy (12), indicating that further research is needed to evaluate these changes with more precise techniques such as MRI.
it needs to be mentioned that our findings were obtained from young men and must therefore not necessarily be valid for female subjects or individuals of different ages.
Conclusion
The present study demonstrated that low-load (20–35% 1RM) blood flow restriction training can induce muscular and tendinous adaptations that are similar to high-load (70–85% 1RM) resistance training. These results are of high relevance for both sports and rehabilitation settings when the lifting of high training loads is contraindicated. Future studies, however, are required to further investigate potential adaptive mechanisms and strengthen the evidence for LL-BFR training in various populations including clinical patients.
Title
Effects of low-load resistance training with vascular occlusion on the mechanical properties of muscle and tendon
Citation
Kubo K, Komuro T, Ishiguro N, Tsunoda N, Sato Y, Ishii N, Kanehisa H, Fukunaga T. Effects of low-load resistance training with vascular occlusion on the mechanical properties of muscle and tendon. J Appl Biomech. 2006 May;22(2):112-9. doi: 10.1123/jab.22.2.112. PMID: 16871002.
Key Notes
Abstract
9 participants
One leg was trained using low load (20%) of 1RM with vasulor occlusions while the othe rleg was using high load (80% of 1RM) without vascular occlusion
Specifica tension and tendon properties were found to remain following low-load resistance training with vascular occlusion, whereas they increased signifi cantly after high-load training.
Introduction
Recent studies using ultrasonography demonstrated that the stiffness of human tendon increased after higher load resistance training
we have reported that the isometric training regimen using higher internal muscle force increased tendon stiffness whereas that using a lower force level did not
Methods
9 healthy young men
Extremely limited sample size
All men
Trained 3x/week for 12 weeks
One leg was trained using the low load with vascular occlusion (LLO) while the other leg was trained using the high load without vascular occlusion (HL)
Doesn’t say the % occlusion pressure
Ultrasound was used to measure the stiffness of the tendon
Discussion
In the present study, there was no signifi cant difference in the relative increase of muscle volume between LLO and
However, the relative increase in MVC tended to be lower for LLO than for HL (p = 0.107). One possible reason for the difference in the increment of MVC between two protocols might be a change in the activation level of the quadriceps femoris muscles
In the present study, the activation levels of the quadriceps femoris muscles assessed by surface electromyogram and twitch-interpolation technique increased signifi cantly for HL, but not for LLO
Thus it seems reasonable to suppose that the low-load with occlusion trainIng induces hypertrophy without the increment of activation level, whereas muscle size and activation level increase after high-load resistance training.
In the present study, the stiffness of both the tendon-aponeurosis complex and patella tendon did not change after low-load training with vascular occlusion
When resistance exercise was performed with occlusion, an elevated energy consumption and repeated muscle contractions with the increase in intramascular pressure would have complex effects on blood circulation and accumulation of lactate
The lactate is produced in response to tissue hypoxia and is a strong stimulator of collagen production by resident tissue macrophages
Therefore, it was hypothesized that tendon stiffness increased for LLO protocol by the accumulation of lactate due to vascular occlusion
However, this hypothesis was not borne out in the present study.
Our recent observation showed that the isometric training regimen using higher internal muscle force led to an increase in tendon stiffness, whereas that using lower force level did not
The ultimate strength of tendons after low-load training with vascular occlusion would not provide the strength corresponding to the increment of muscle strength after training. Furthermore, it may safely be assumed that this leads to tendon injuries.
In conclusion, the present study demonstrated that low-load resistance training with vascular occlusion did not alter the specifi c tension and stiffness of the tendon-aponeurosis complex, while high-load training increased it signifi cantly. These results suggested that low-load resistance training with vascular occlusion did not affect the motor unit activation of muscle and tendon properties.
Title
Effects of Blood Flow Restriction Training on Handgrip Strength and Muscular Volume of Young Women
Citation
Fernandes DZ, Weber VMR, da Silva MPA, de Lima Stavinski NG, de Oliveira LEC, Casoto Tracz EH, Ferreira SA, da Silva DF, Queiroga MR. EFFECTS OF BLOOD FLOW RESTRICTION TRAINING ON HANDGRIP STRENGTH AND MUSCULAR VOLUME OF YOUNG WOMEN. Int J Sports Phys Ther. 2020 Dec;15(6):901-909. doi: 10.26603/ijspt20200901. PMID: 33344006; PMCID: PMC7727424.
Key Notes
Introduction
The mechanisms by which the physiological changes occur are not completely known;
however, they seem to be associated with hypoxia and muscular acidosis, which produces a rapid and intense fatigue due to the lower oxygenation and high stimulation of metabo receptors. The poor oxygen environment may also increase Type II muscle fiber recruitment in order to maintain the intensity of contraction, which can lead to the strength gains previously reported
Methods
28 female students
Included subjects were female, untrained (i.e., not engaged in an exercise training program for at least six months),
Right handed
Aged between 18-25 years old
Sessions 3x/week
4 weeks only
The right (RHGS) and left (LHGS) handgrip strength were determined using a manual dynamometer
Results
There were no significant differences for any of the variables analyzed, showing the homogeneity among groups.
Discussion
Interestingly, the magnitude of the effects of the intervention on handgrip strength was similar in both groups, but with a greater effect on training the left hand than the right hand.
In other words, both handgrip strength training (BFR and TRAD) promoted greater effect in the limb with the lower pre-intervention strength level
The findings of the present study are in accordance with the literature, in which, a similar strength gain between BFR and TRAD has been observed in several populations
However, the information about ES suggests that high intensity training is slightly more efficient for strength gain when compared to flow restriction training.
This may be justified by the greater recruitment of motor units in high-intensity training in relation to training in low-intensity blood flow restriction.
Among the limitations of this study, the relatively short intervention time (30 days or 12 sessions) should be highlighted.
Title
Upper-extremity blood flow restriction: the proximal, distal, and contralateral effects-a randomized controlled trial
Citation
Bowman EN, Elshaar R, Milligan H, Jue G, Mohr K, Brown P, Watanabe DM, Limpisvasti O. Upper-extremity blood flow restriction: the proximal, distal, and contralateral effects-a randomized controlled trial. J Shoulder Elbow Surg. 2020 Jun;29(6):1267-1274. doi: 10.1016/j.jse.2020.02.003. PMID: 32423577.
Key Notes
Introduction
This is believed to occur through upregulation of stress-induced gene expression that potentiates cellular swelling, protein synthesis, and hormone Production, both Local and systemic.
Although mechanical tension remains the primary drive for muscle hypertrophy, low-load BFR appears to induce metabolic stress with less exertion by concentrating these signaling factors.
We hypothesized that patients training with low-weight BFR would have significantly increased strength, hypertrophy, and endurance proximal, distal, and contralateral to cuff placement compared with low-weight training alone at 6 weeks.
Methods
Individuals were excluded if they had a history of shoulder or upper-extremity pathology requiring surgery or therapy, a history of venous thromboembolism, a clotting or other hematologic disorder, coronary artery disease, peripheral arterial disease, or hypertension
6 weeks of training
2 training sessions per week
Upper-extremity strength was assessed at baseline and follow-up using isokinetic testing for shoulder internal and external rotation and by dyna Mometer For Shoulder Scaption, shoulder Flexion shoulder abduction, elbow flexion, elbow extension, and grip strength.
60% arterial occlusion in the extremity
30 repetitions, followed by 30 seconds of rest; set 2, 15 repetitions, followed by 30 seconds of rest; set 3, 15 repetitions, followed by 30 seconds of rest; and set 4, 15 repetitions
Results
Low-weight BFR training provided a greater increase in strength and hypertrophy in the upper-extremity proximal and distal muscle groups compared with the control group. The non-BFR extremity showed a significant increase in grip strength compared with the control group, indicating a potential systemic effect
Title
Blood Flow Restriction Training for the Rotator Cuff A Randomized Controlled Trial.
Citation
Brumitt J, Hutchison MK, Kang D, Klemmer Z, Stroud M, Cheng E, Cayanan NP, Shishido S. Blood Flow Restriction Training for the Rotator Cuff: A Randomized Controlled Trial. Int J Sports Physiol Perform. 2020 Aug 19:1-6. doi: 10.1123/ijspp.2019-0815. Epub ahead of print. PMID: 32820139.
Key Takeaways
Abstract
Abstract: Context: Blood flow restriction (BFR) training utilizes a tourniquet, applied to the proximal portion of one or more extremities, to occlude blood flow during exercise. Significant gains in strength and cross-sectional area can be achieved in muscles, both distal and proximal to BFR cuff application. Purpose: To compare strength gains of the rotator cuff and changes in tendon size in subjects who performed side-lying external-rotation exercise with or without BFR. Methods: Forty-six subjects (mean age 25.0 [2.2] y) were randomized to either a BFR + exercise group or to the exercise-only group. Subjects performed 4 sets of the exercise (30/15/15/15 repetitions) at 30% 1-repetition maximum 2 days per week for 8 weeks. Results: Subjects in both groups experienced strength gains in the supraspinatus and the external rotators (P =.000, P =.000). However, there was no difference in strength gains between groups for the supraspinatus (P =.750) or the external rotators (P =.708). Subjects in both groups experienced increases in supraspinatus tendon thickness (BFR P =.041, exercise only P =.011). However, there was no difference between groups (P =.610). Conclusions: Exercise with BFR applied to the proximal upper extremity did not augment rotator cuff strength gains or tendon thickness when compared with subjects who only exercised. This study did demonstrate that performing multiple sets of high repetitions at a low load led to significant increases in rotator cuff strength and tendon size in the dominant upper extremity.
Introduction
There are several proposed mechanisms associated with the aforementioned gains during BFR training including metabolite accumulation, growth hormone release, mammalian target of rapamycin complex 1 activation, downregulation of myostatin, and cellular swelling
The purpose of this study was to compare strength gains of the supraspinatus and the external rotators of the shoulder and changes in tendon size of the supraspinatus in subjects who performed the sidelying external rotation (ER) exercise with or without BFR.
Methods
twice-weekly exercise sessions, for 8 weeks
limb occlusion pressure set to 50%
with 46 subjects (women = 20, men = 26;
Results
All subjects experienced significant increases in strength for the supraspinatus (P = .000) and for the external rotators (P = .000); however, there was no difference between groups (P value = .750 for the supraspinatus; P value = .708 for the external rotators)
All subjects in both groups experienced significant increases in supraspinatus tendon thickness, However, there was no difference between groups
Discussion
The results of this study demonstrate that the use of BFR did not augment increases in strength or tendon thickness when compared with subjects who exercised without BFR. This study did demonstrate that the performance of the sidelying ER exercise, performed twice a week for 8 weeks, led to significant increases in rotator cuff strength and supraspinatus tendon thickness regardless of group allocation.
It is possible that the application of the BFR cuff to the proximal upper extremity may not facilitate the same physiologic response that has been observed when the lower extremity(-ies) are occluded.
For example, a 2 exercise program for the lower extremities had a significantly greater increase in growth hormone concentration when compared with performing a 2 exercise program for the upper body
Conclusion
The performance of the sidelying ER exercise with BFR applied to the proximal upper extremity did not augment rotator cuff strength gains or supraspinatus tendon thickness when compared with subjects who only exercised. This study did demonstrate that performing multiple sets of high reps performed at a low load led to significant increases in rotator cuff strength and supraspinatus tendon size in the dominant upper extremity
Title
Blood Flow Restriction Training for the Shoulder: A Case for Proximal Benefit
Citation
Lambert B, Hedt C, Daum J, Taft C, Chaliki K, Epner E, McCulloch P. Blood Flow Restriction Training for the Shoulder: A Case for Proximal Benefit. Am J Sports Med. 2021 Aug;49(10):2716-2728. doi: 10.1177/03635465211017524. Epub 2021 Jun 10. PMID: 34110960.
Key Takeaways
Introduction
Because metabolic and mechanical stress is primarily experienced by muscles distal to the site of occlusion, one may speculate that proximal muscles (where blood flow is not occluded) may not experience the same stimulatory effects with regard to changes in strength and muscle mass. However, it has been postulated that BFR can provide benefits to muscle groups directly proximal to the site of occlusion via local paracrine or systemic action as well as elevated muscle fiber recruitment
hard data regarding the efficacy of BFR beyond anecdotal reporting are extremely limited
Although promising results have been reported for the use of BFR for upper body rehabilitation, controlled studies on the effects of BFR for rehabilitation or preventive training on the rotator cuff or shoulder musculature as a whole are insufficient
previous review literature has proposed that enhanced muscle activation (inferred from electromyography [EMG]) of proximal muscles as a result of occlusion-induced distal fatigue may contribute to enhanced proximal benefit as a result of compensation for fatigued distal muscles.
the purpose of this study was to compare 8 weeks of combined BFR and Low-intensity exercise (BFR-LIX) versus Low-intensity exercise alone (LIX) with regard to chronic changes in shoulder lean mass, upper extremity lean mass, rotator cuff strength, muscular endurance, and acute EMG amplitude
Methods
A total of 35 untrained healthy adults (age, 18-45 years) were recruited to participate
final sample size of 32
(BFR group, 13 men, 3 women; No-BFR group, 10 men, 6 women).
Lean mass = DEXA scan
Within 1% to 6% error with excellent reliability between measurements
8 weeks of bilateral training:
cable ER at 0, cable IR at 0, dumbbell scaption, and side-lying dumbbell ER at 0
Results
Only the BFR group had a significant increase in upper extremity lean mass
Discussion
The results indicated that the addition of BFR (applied at 50% LOP) to the proximal arm effectively augmented increases in shoulder muscle mass, endurance, and some parameters of isometric strength when combined with the standard rotator cuff training exercises commonly used in clinical and athletic training settings.
Hypothesize that these results are attributable, in part, to greater acute activation of deltoid and rotator cuff muscles observed under occluded conditions
Title
Low-Load Blood Flow Restriction and High-Load Resistance Training Induce Comparable Changes in Patellar Tendon Properties
Citation
Centner C, Jerger S, Lauber B, Seynnes O, Friedrich T, Lolli D, Gollhofer A, König D. Low-Load Blood Flow Restriction and High-Load Resistance Training Induce Comparable Changes in Patellar Tendon Properties. Med Sci Sports Exerc. 2022 Apr 1;54(4):582-589. doi: 10.1249/MSS.0000000000002824. PMID: 34772900.
Key Notes
Discussion
Although high-level evidence indicates that LL-BFR training is a potent stimulator of myofibrillar muscle protein synthesis (37,38) and elicits both structural and functional muscle adaptations (9,10), the literature is still scarce on the effects on the human tendinous system.
First experiments by Kubo and colleagues (20) in 2006 compared LL-BFR and HL training on mechanical and morphological adaptations of the patellar tendon. After 12 wk of resistance training, their findings pointed toward beneficial effects after HL but unchanged tendon properties after LL-BFR.
However, LL-BFR training effects may have been missed in that publication because of suboptimal load matching between training groups
After 14-wk of mechanical loading (either HL or LL-BFR), we found that Achilles tendon stiffness significantly increased
Moreover, the training duration was increased from 12 wk (20) to 14 wk according to previous suggestions for optimal tendon adaptations
Interestingly, earlier studies have reported that besides GH, additionalmetabolic factors such as lactate are involved in collagen production and tendon cell proliferation
From a mechanistic point of view, we assume that tendinous adaptations are not merely mechanical stress and strain dependent (as evidenced by previous work [8]) but also strongly rely on the metabolic environment. By restricting venous outflow from the muscle, BFR facilitates a local hypoxic milieu and leads to an accumulation of numerous anabolic growth factors (39) and metabolites (40,41). Among the potential candidates, which might mediate tendon adaptations, is growth hormone (GH).
However, the physiological mechanisms behind the effects of LL-BFR on tendon stiffness remain speculative and cannot be ascertained in the current study because this was beyond the scope.
From a mechanistic point of view, we assume that tendinous adaptations are not merely mechanical stress and strain-dependent (as evidenced by previous work [8]) but also strongly rely on the metabolic environment. By restricting venous outflow from the muscle, BFR facilitates a local hypoxic milieu and leads to an accumulation of numerous anabolic growth factors (39) and metabolites (40,41). Among the potential candidates, which might mediate tendon adaptations, is growth hormone (GH).
Title
Changes in Basal Levels of Testosterone, Cortisol and Their Ratio after 4 Weeks of Rock Climbing Training with Blood Flow Restriction in Elite Male Rock Climbers
Citation
Ebadifar, K., Matinhomaee, H., Banaeifar, A. (2021). Changes in Basal Levels of Testosterone, Cortisol and Their Ratio after 4 Weeks of Rock Climbing Training with Blood Flow Restriction in Elite Male Rock Climbers. Journal of Sport Biosciences, 13(1), 59-73. doi: 10.22059/jsb.2021.312058.1440
Title
Effects of 4 weeks resistance training with and without blood flow restriction on GH, IGF-1, NO and Lactate in male rock climbers
Citation
Sanei, P., vakili, J., amirssan, R. (2021). Effects of 4 weeks resistance training with and without blood flow restriction on GH, IGF-1, NO and Lactate in male rock climbers. Journal of Sport Biosciences, (), -. doi: 10.22059/jsb.2021.323313.1468
Title
Effect of 4 Weeks of Rock Climbing with and without Blood Flow Restriction, on Serum Levels of CRP, LDH and CK in Elite Rock Climbers.
Citation
Halalkhor, Fateme, et al. “Effect of 4 Weeks of Rock Climbing with and without Blood Flow Restriction, on Serum Levels of CRP, LDH and CK in Elite Rock Climbers.” Journal of Sport and Exercise Physiology, vol. 13, no. 2, 2021, pp. 75–85., https://doi.org/10.52547/joeppa.13.2.75.
Title
The effects of acute blood flow restriction on climbing-specific tests.
Citation
Saeterbakken, A., Andersen, V., Stien, N., Pedersen, H., Solstad, T., Shaw, M .. & Hermans, E. (2020). The effects of acute blood flow restriction on climbing-specific tests. Movement & Sport Sciences, 109, 7-14. https://doi.org/10.1051/sm/2020004
Key Takeaways
The results demonstrated no differences in the isometric strength tests (p = 0.496–0.850, ES = 0.060–0.170), dynamic strength test (p = 0.226–0.442, ES = 0.200–0.330) or the intermittent finger endurance test (p = 0.563, ES = 0.160). In conclusion, no differences were observed in the maximal isometric pull-up test, dynamic pull-up test or finger endurance tests including measurements as peak force, MVC, RFD, power output, peak velocity or time to fatigue at 60% of MVC with and without BFR
Title
Mechanisms Behind Blood Flow-Restricted Training and its Effect Toward Muscle Growth
Citation
Hwang PS, Willoughby DS. Mechanisms Behind Blood Flow-Restricted Training and its Effect Toward Muscle Growth. J Strength Cond Res. 2019 Jul;33 Suppl 1:S167-S179. doi: 10.1519/JSC.0000000000002384. PMID: 30011262.
Key Takeaways
Hypertrophic Adaptations: Hormone Responses
Occlusion training or BFR training is known to induce metabolic accumulations, which may include biomarkers such as whole blood lactate, plasma lactate, and muscle cell lactate
The accumulation of these metabolites is known to present an acidic intramuscular environment through which the stimulation of sympathetic nerve activity is mediated by intramuscular metaboreceptors and group III and IV afferent fibers
Growth Hormone
The accumulation of these metabolites is known to present an acidic intramuscular environment through which the stimulation of sympathetic nerve activity is mediated by intramuscular metaboreceptors and group III and IV afferent fiber
Many scientists believe that GH primarily functions to assist in the overall process of skeletal muscle hypertrophy through the potentiating release of insulin-like growth factor-1 (IGF-1) (66). However, other researchers believe that MPS may require the additive approach of both GH and IGF-1 concentrations
The implementation ofBFR training in 1 study has been found to elevate GH levels to ~290x
It is known that the implementation of Kaatsu training increased the postexercise GH levels 10-fold above the control group with no blood flow–restriction
Another study examined the exogenous administration of GH in combination with resistance exercise, which has not shown significant effects toward MPS
Several other studies have implemented the exogenous administration of reCombinant GH with the induction of resistance exercise, which has not shown greater levels of muscle protein growth
Therefore, even with these conflicting results, the physiological significance of GH secretion and its possible association with blood flow restriction and skeletal muscle hypertrophy definitively necessitate further research.
Peptide Hormone IGF-1
Increases in protein levels of IGF-1 havebeen shown to be proportional toward increases within muscular strength after sessions of resistance exercise (
One study found that resistance training with vascular occlusion showed increases within circulating levels of IGF-1 alongside the growth in muscle volume
However, presently, it is still unclear whether IGF-1 activity is increased directly in response to occlusion training.
Another study found increases within IGF-1 activity in response to low-intensity occlusion training 72). In stark contrast, a study by Kawada and Ishii found no significant increases in IGF-1 after a bout of occlusion training, which may be due to factors such as the intensity levels or frequency of the training program
There are many conflicting findings behind whether the low-intensity exercise–induced occlusion training protocols have an effect toward elevating IGF-1 levels after exercise (5,15,18), which may necessitate further studies with minimal methodological differences to confirm the potential associations that IGF-1 hormonal levels may have toward the induction of BFR training.
Anabolic Hormone: Testosterone
It is widely established in the literature that testosterone carries forth anabolic effects on MPS and the decreasing of muscle cell proteolysis
Several Kaatsu-related studies have found no significance in postexercise elevated levels of testosterone after BFR exercise sessions
Satelite Cells
Muscle protein synthesis is achieved through this activation of the insulin-like growth factor 1-phosphoinositide-3-kinase-Akt/protein kinase B-mammalian target of rapamycin (IGF1-PI3K-Akt/PKB-mTOR) signaling pathway and the downregulation of the myostatin-Smad 3 pathway, which is known as a negative regulator of skeletal muscle growth
A study found that the implementation of occlusion training upregulated the phosphorylation of S6K1 at Thr389 3-fold after exercise session and continued to be elevated relative to the control 3 hours after exercise bout
According to the literature, it is also known that a single bout of low-intensity resistance exercise with blood flow restriction can result in both an upregulation of the anabolic cell signaling mTOR pathway within 3 hours after exercise and a downregulation of the proteolytic transcripts for skeletal muscle at 8 hours after exercise
Another study found that acute low-load resistance exercise with blood flow restriction (30% 1RM unilateral knee extensions with 5 sets to failure on both BFR and free-flow leg) resulted in the enhancement of phosphorylation of p70S6K at Thr389 at 1 hour and 24 hours after exercise
In addition, this study by Wernbom et al. (80). found an elevation of p38MAPK and increased numbers of SCs within the BFR leg compared with the free-flow leg 1 hour after exercise
Therefore, it is hypothesized that occlusion training may induce muscle hypertrophy due to the repressed activity of myostatin due to either hypoxia conditions or metabolite accumulation due to BFR training
Fiber Type Recruitment
BFR training can recruit FT fibers without regards to the widely accepted size prin ciple in which ST fibers are recruited first with FT fiber being recruited as intensity progresses.
The rationale presented throughout the literature may be due to the hypoxia conditions created by the vascular occlusion through which the additional recruitment of more motor units may take place to compensate for the deficit in overall force development
In addition, the metabolite accumulations throughout the BFR training session may also induce the increased recruitment of FT or higher threshold motor units
Several studies show through the utilization of electromyography (EMG) that during Kaatsu training, there was an increase in the recruitment of FT muscle fibers
Another study that implemented low-intensity vascular occlusion training showed early fatigue of type I fibers due to the lack of delivery in oxygen, thus showing a greater increase in the CSA of type II fibers by 27.6% compared with type I muscle fibers increase of 5.9% during a 2-week training program at 20% of 1RM
However, there is still a necessitation of further research to confirm whether increased FT fiber recruitment during BFR training has a direct association with the metabolically induced skeletal muscle growth.
Conclusions
The implementation of low-intensity resistance exercise (20–50% 1RM) training under the condition of blood flo restriction can be an effective means to elicit skeletal muscle hypertrophy without a high level of mechanical stress on the joints
this review has explicated potential mechanisms behind hypertrophic adaptations associated with BFR training such as hormonal responses, intracellular signaling pathways, SC activity, and fiber type recruitment patterns. Future studies should specifically explore the mechanisms responsible for both acute and chronic hypertrophic adaptations after BFR training.
The potential risks and danger associated with BFR training due to vascular occlusion and pressure differences of the applied cuff may stir skepticism within this novel training modality. However, the results of a national study showed that the implementation of a Kaatsu training program within 12,642 individuals (male 45.4% and female 54.6%) of various age ranges (younger than 20 to older than 80 years) displayed minor incidences of side effects such as venous thrombus (0.055%), pulmonary embolism (0.008%), and rhabdomyolysis (0.008%)
Nevertheless, the methodologies behind the use of BFR training such as the standardization of cuff pressures, perceived rate of pain, changes in cuff widths, and type of material should be still explored in future studies to mitigate further skepticism behind this potentially beneficial training modality.
Furthermore, the integration of low-intensity blood flow restriction in conjunction with a high-intensity progressive resistance training program have been suggested to optimize a greater capacity for recovery while still promoting sound muscular development over time
Because low loads of BFR exercise presents a different neural stimulus in comparison with high-intensity resistance training, any optimal gains in muscular strength or hypertrophic adaptations may require conjunctive combinations of low-load BFR and traditional high-intensity training
Title
Options for basing Dietary Reference Intakes (DRIs) on chronic disease endpoints: report from a joint US-/Canadian-sponsored working group.
Citation
Yetley, Elizabeth & MacFarlane, Amanda & Greene-Finestone, Linda & Garza, Cutberto & Ard, Jamy & Atkinson, Stephanie & Bier, Dennis & Carriquiry, Alicia & Harlan, William & Hattis, Dale & King, Janet & Krewski, Daniel & O'Connor, Deborah & Prentice, Ross & Rodricks, Joseph & Wells, George. (2016). Options for basing Dietary Reference Intakes (DRIs) on chronic disease endpoints: report from a joint US-/Canadian-sponsored working group. American Journal of Clinical Nutrition. 105. 10.3945/ajcn.116.139097.
Title
The effects of a 7-week practical blood flow restriction program on well-trained collegiate athletes
Citation
Luebbers PE, Fry AC, Kriley LM, Butler MS. The effects of a 7-week practical blood flow restriction program on well-trained collegiate athletes. J Strength Cond Res. 2014 Aug;28(8):2270-80. doi: 10.1519/JSC.0000000000000385. PMID: 24476782.
Disclaimer:
As always, exercises are to be performed assuming your own risk and should not be done if you feel you are at risk for injury. See a medical professional if you have concerns before starting new exercises.
Written and Presented by Jason Hooper, PT, DPT, OCS, SCS, CAFS
IG: @hoopersbetaofficial
Filming and Editing by Emile Modesitt
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