Dr. Christopher Brandner is a Sports Scientist and Strength and Conditioning Coach at Aspire Academy for Sports Excellence in Doha, Qatar. In 2016, he received his Ph.D. from Deakin University in Melbourne, Australia, where his research examined the acute and chronic training adaptations to resistance exercise with blood flow restriction.
Freelap USA: What are the benefits of blood flow restriction (BFR) training, beyond just athletes lifting lighter to get strength changes? Any ideas on possible adaptations outside of gains in hypertrophy or muscle strength?
Dr. Brandner: Compared to heavy load (> 70% 1RM) resistance training, BFR training has been shown to induce similar muscular adaptations (strength and size), with reduced training loads (% 1RM), volume (total number of repetitions completed with BFR vs non-BFR), and training durations. The efficacy of combining light loads (20-40% 1RM) during resistance exercise goes far beyond that of just improving strength and muscle size for athletes.
BFR training provides an anabolic stimulus without the need for heavy mechanical loads. For trained individuals, this type of training also produces minimal muscle damage post-exercise. This means that higher training frequencies can potentially be used (for example, BFR has been shown to be effective in track & field athletes with a twice-daily training stimulus across eight consecutive days), which perhaps result in quicker adaptations in strength and size (although this study did not compare the same training versus a heavy load group), as well as improved 10-30 meter times. Other studies using athletes have observed performance benefits in vertical jump height, 505 agility and 20-meter shuttle run tests.BFR training provides an anabolic stimulus without the need for heavy mechanical loads. Click To Tweet
This type of training also has some obvious implications for athletes rehabilitating from injury (which is discussed later in some detail), and other clinical populations such as the elderly.
One of my favorite studies in this area, despite its limitations, was conducted on Japanese male collegiate basketball players. The athletes performed treadmill walking exercise (five sets of three minutes at 4-6 km/hour, with 60 second intra-set rest periods) twice daily for two weeks (12 days total), either with or without BFR. The BFR group improved maximal aerobic capacity and ventilation (11.6% and 10.6%, respectively) but there were no changes for the control group. Unfortunately, one recent study didn’t show the same positive results in highly trained Navy Seal Warfare Operators, but this type of information may provide further evidence for coaches about the use of BFR for cardiovascular adaptations.
We know that BFR can stimulate central hemodynamics such as heart rate, blood pressure, and stroke volume to a point somewhere between performing high- or low-intensity exercise, and practitioners have attempted to replicate this normal orthostatic stress during space flight. Vascular adaptations to both resistance and aerobic exercise are also possible, with improved blood flow and increased number of capillaries also a benefit of short-moderate length training durations (four to eight weeks). I have a small suspicion that this adaptation also plays a role in enhancing the rehabilitation process.
Freelap USA: Due to the anatomy of the circulatory system dictating what areas of the body can benefit, can you share the best and worst responders to BFR? I am sure many of the propulsive muscles are good responders, but the trunk is likely not a good idea.
Dr. Brandner: You would be right in thinking that, too. When using BFR, the cuffs are placed across the most proximal part of the arm or leg in order to restrict the major artery (brachial and femoral, respectively). Therefore, it is common to see literature focus on single-joint isolation exercises such as the biceps curl, knee extension, and flexion.
Interestingly though, studies (and recent meta-analysis) have shown that compound exercises such as the squat and bench press with BFR can also benefit. Indeed, changes in both muscle strength and size can be observed in the non-restricted trunk musculature following training. This has particularly been shown following bench press training with increases in muscle thickness of the triceps brachii and the pectoralis major (as well as 1RM strength). However, a group training with heavy loads showed much larger increases, so while BFR can benefit some muscles of the trunk, these might be smaller than traditional training. Additionally, if repeated over long training durations, it could result in muscular imbalances between the limb and trunk muscles.
Freelap USA: What are the risks of BFR training? With some recreational weightlifters getting involved, what should be known before starting with BFR? As mentioned earlier, everyone needs to be familiar with anatomy and physiology first.
Dr. Brandner: First, I wouldn’t recommend that anyone reading this go straight out and purchase restrictive cuffs or elastic wraps and start blindly trying to reduce blood flow during exercise! This can be dangerous and result in some serious side effects. But if BFR training is done correctly by experienced practitioners who have knowledge in the area, then the evidence suggests that it is a safe training modality.BFR is a safe training modality when done correctly by experienced, knowledgeable practitioners. Click To Tweet
Dr. Stephen Patterson (St Mary’s University, U.K.) and I recently published the results from a questionnaire-based survey of practitioners such as strength and conditioning coaches and physiotherapists using BFR in the field and in research. We asked the practitioners about their perceived contraindications to BFR and any reported side effects.
Practitioners were concerned with potential issues of deep vein thrombosis, blood clotting disorders, and hypertension. The good news is that there has been no evidence (though it is limited at this stage) of any deleterious vascular responses (such as damage to the endothelium). In fact, there are many studies that have shown improved blood flow post-exercise and increased angiogenesis (new blood vessel formation). The largest reported side effects were delayed onset muscle soreness, numbness, dizziness, and bruising, but these are normally short-lived responses. There have been reports of rhabdomyolysis (a break down in skeletal muscle) following BFR, but this can be independent of the use of BFR and simply a response to being unaccustomed to exercise (which we have seen in our labs in untrained participants after light load training without BFR).
Overall, practitioners and their client/athletes need to be aware of the possible risks of BFR training, and how to safely prescribe BFR. The key here seems to be in the prescription of the restriction pressure, which should be individualized to the maximal limb occlusion pressure (i.e., the highest pressure measured using Doppler ultrasound before blood flow ceases). Studies have shown that percentages of 40-90% are efficacious for training, but if you are still unsure, it would be best to err on the side of caution and perform BFR at the lower end of the spectrum (40-60% of maximal limb occlusion pressure). This has been shown to be just as efficacious as higher percentages. A pre-exercise risk assessment tool has also been developed and published recently for practitioners.
Freelap USA: Some coaches believe that BFR doesn’t help as much for power because of the nervous system adaptations required for high-velocity work. Could you share when BFR is appropriate for speed and power athletes, and when other modalities make more sense?
Dr. Brandner: Some studies have shown improvements in countermovement jump and sprint times for athletes following short-term (i.e., less than six weeks) BFR training, while others have not. I don’t think there is enough evidence to say that BFR can be beneficial for improvement in maximal power, and changes in muscle strength following BFR training may be more closely related to rapid increases in muscle hypertrophy as opposed to neural adaptations. (Although there is evidence of both central and peripheral neural adaptations, at least in untrained populations.) Therefore, I don’t think it would be appropriate to use light load resistance exercise with BFR as a single intervention, if that was the purpose of training, and I would agree with the coaches. While I think BFR can be an effective training stimulus, I am a big believer that if you can lift heavy then you should continue to do so, but also that a combination of the two training modes may work best.
In saying that, there are a number of likely benefits of using BFR for speed, strength, and power athletes, including:
1. Rehabilitation from injury or surgery: The use of light loads is appealing for strength and conditioning coaches to apply training to injured athletes looking to improve recovery times, and minimize the loss in strength, size, and function during the recovery. A progressive rehabilitation program has recently been proposed and involves: a) Passive BFR (no exercise) during bed rest or immobilization; b) BFR combined with light intensity aerobic (cycling or walking) exercise; c) BFR combined with light load resistance exercise, and; d) BFR training combined with heavy load training and then a return to competition.
One of the more famous examples of BFR in a rehabilitation setting is with an American Nordic skier, Todd Lodwick, who broke his leg and shoulder, and tore ligaments during practice only a few weeks out from the 2014 Winter Olympics. During his recovery, he used BFR training and went on to finish sixth in the finals after being presented as the flagbearer for the U.S.A. Olympic team.
2. Use during travel for training and competition: Some sports have chaotic training and competition schedules, which means coaches and athletes are often away from their ideal training facilities. While mechanic pressurized devices and cuffs such as those used in research are relatively expensive and can typically only be used with single users at a time, elastic wraps and tourniquets are more cost- and time-effective devices (albeit with less control of the pressure stimulus applied). Combining BFR with body weight exercises or weighted vests, or the use of elastic resistance bands, can improve or at least maintain muscular adaptations on the road during travel.
3. Reduced training loads and time: Combining BFR with light loads may be useful for athletes to provide an anabolic training stimulus without high mechanical loads and the associated muscle damage. Training sessions are also normally shorter than traditional training, due to the reduced intra-set rest periods (30-60 seconds), which decreases training duration.
4. Reducing pain: While perceptual responses of pain and perceived exertion are known to be high during BFR exercise, a little-known fact is that BFR can also reduce pain post-exercise. Researchers from Aspetar Medical Hospital in Qatar have found that performing BFR exercises with patients with anterior knee pain reduces their pain scores (measured on a visual analog scale) immediately post-exercise, and allows them to continue with their traditional heavy load training after receiving the intervention.A little-known fact is that blood flow restriction can reduce pain post-exercise. Click To Tweet
Freelap USA: What are your thoughts on contact sports using BFR after games as a way to train better? When there’s a need to lift but circumstances make it hard, is it an idea worth exploring?
Dr. Brandner: I guess it depends on what the purpose of the training is, and how long after the competition you want to begin training (or how long post-competition you are fully recovered enough to begin training). Some forms of BFR without exercise have been used to speed up the recovery process—for instance, recovery boots have become quite popular and provide compression to the limbs to improve blood flow and remove waste products following exercise by effectively mimicking the muscle pump. But this question refers more to performing training sooner with BFR post-competition due to the reduced mechanical demand on the neuromuscular system.
I am not aware of any scientific literature available that has used BFR training after games in order to begin training for the next competition. I guess that as much as we like to be evidence-based coaches, sometimes the published literature is lagging behind what is innovatively being done in the field. Depending on the nature of the sport, the amount and impact of contacts, recovery time between competition days, and individual factors (training age), I believe BFR could be used as a training stimulus for athletes that have a limited capacity for recovery from competition and those with weakened immune systems.
Reduced training intensities during both resistance and aerobic exercise with BFR may allow athletes to continue to improve, or at the very least maintain, their muscular development or aerobic fitness between competition days. Once the athlete’s recovery metrics and wellness have improved post-competition, a good holistic training program involving high loads and high intensities later in the training week should still be the goal when the athlete is able to tolerate the loads.
Since you’re here…
…we have a small favor to ask. More people are reading SimpliFaster than ever, and each week we bring you compelling content from coaches, sport scientists, and physiotherapists who are devoted to building better athletes. Please take a moment to share the articles on social media, engage the authors with questions and comments below, and link to articles when appropriate if you have a blog or participate on forums of related topics. — SF