#179 - Jeremy Loenneke, Ph.D.: The science of blood flow restriction—benefits, uses, and what it teaches us about the relationship between muscle size and strength
Oct 11, 2021
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Jeremy Loenneke, an Associate Professor of Exercise Science at the University of Mississippi, dives deep into blood flow restriction (BFR) training. He reveals how BFR can promote muscle growth with lighter loads and discusses the anatomy of muscle fibers. Loenneke challenges the traditional link between muscle size and strength, presenting fascinating research findings. He shares practical advice for incorporating BFR into workouts, whether for athletes or average folks, and explores its applications in rehabilitation.
Blood flow restriction training allows individuals to achieve muscle growth and strength adaptations with lighter loads.
Proper technique, understanding individual tolerance, and using appropriate loads are key factors in minimizing risks and ensuring a safe training experience.
BFR can be considered a safe and effective training method for individuals looking to enhance their fitness levels.
BFR offers a valuable alternative for those who are unable or prefer not to lift heavy weights.
Deep dives
Blood Flow Restriction Training and its Origins
Blood flow restriction training, also known as BFR, originated from the experiments of Sato Yao in the 1970s. His experience of feeling numbness while kneeling led him to experiment with ways to restrict blood flow and its potential benefits on muscle growth and strength. He found that by applying pressure with cuffs or wraps to the limbs during exercise, it allowed individuals to use lower weights while still achieving similar muscle adaptations as with heavy lifting.
Application of Blood Flow Restriction
To apply blood flow restriction, it is recommended to use cuffs or wraps that restrict blood flow by a certain percentage of an individual's arterial occlusion pressure. The pressure is typically set at 40% to 80% of the arterial occlusion pressure. The wraps should not be so tight as to completely exclude blood flow, but rather reduce blood flow into the muscle. For resistance exercise, it is suggested to start with 4 sets of an exercise and gradually increase the number of exercises, with rest periods of approximately 30 seconds between sets. For aerobic exercise, longer durations of blood flow restriction can be used, but it is important to monitor discomfort levels and adjust pressure accordingly.
Benefits and Considerations of Blood Flow Restriction
Blood flow restriction training enables individuals to achieve muscle growth and strength adaptations with lighter loads. Research suggests that it is effective in promoting muscle hypertrophy and strength gains. However, it is important to use proper technique, such as applying appropriate pressure and using lower loads to prevent excessive discomfort. It is also crucial to monitor and adjust the pressure based on individual tolerance and allow sufficient recovery time between sets. Although blood flow restriction training is generally safe when performed correctly, care should be taken to avoid excessive pressures that may cause nerve damage, and it may not be suitable for individuals with certain medical conditions.
Risks and Safety Profile of Blood Flow Restriction Training
While blood flow restriction training is generally considered safe when performed correctly, there are potential risks to be aware of. These risks include the possibility of nerve damage or compression if excessive pressure is applied or if the wraps are too tight. It is essential to monitor and adjust pressure levels to prevent discomfort or pain. Moreover, individuals should exercise caution and consult a healthcare professional before engaging in blood flow restriction training, especially if they have underlying medical conditions or circulatory issues. Proper technique, understanding individual tolerance, and using appropriate loads are key factors in minimizing risks and ensuring a safe training experience.
Safety of Blood Flow Restriction Training
Blood flow restriction (BFR) training is a safe and effective method that restricts blood flow for short durations during exercise. The safety profile of BFR is comparable to traditional exercise, and it does not increase the risk of blood clots or muscle damage. While there is always a risk associated with any form of exercise, when properly done, BFR does not appear to increase the overall risk. Furthermore, BFR has been found to have a similar or even better hypertrophy response compared to traditional training, allowing for muscle growth and strength gains. Overall, BFR can be considered a safe and effective training method for individuals looking to enhance their fitness levels.
Blood Pressure Response to BFR Exercise
When performing exercises with blood flow restriction, blood pressure is generally higher near the cuff area but comparable to traditional high load exercise. It is important to note that while blood pressure may increase during BFR exercise, it returns to baseline levels within a few minutes. However, individuals with certain clinical conditions may be more sensitive to this blood pressure response, and caution should be exercised. Overall, BFR does not pose significant risks in terms of blood pressure response, particularly when compared to high load exercise.
Hypertrophy and Strength in BFR Training
BFR training can be an effective tool for hypertrophy and strength gains. With BFR, it is possible to achieve similar or even better hypertrophy compared to traditional exercise, despite using lower loads and less volume. The metabolic challenge posed by BFR, including the trapping of metabolites like lactate, can contribute to increased muscle activation and fatigue. As a result, more muscle fibers are recruited during BFR training, leading to efficient muscle growth and strength development. While traditional high load training is still vital for maximum strength gains, BFR offers a valuable alternative for those who are unable or prefer not to lift heavy weights.
Potential Applications of BFR
BFR can have various applications in different populations. It can be particularly beneficial for individuals recovering from injuries or surgeries, as it helps to slow down muscle loss and aid in rehabilitation. BFR can also be used as a tool for hypertrophy training, potentially providing a more efficient means to fatigue the muscles and stimulate muscle growth. Additionally, BFR can offer variety in workouts and may be used to enhance recovery in athletes. While the benefits of BFR are promising, further research is needed to explore its full potential and various applications.
Jeremy Loenneke has a Ph.D. in exercise physiology, a Master’s in nutrition and exercise, and is currently the director of the Kevser Ermin Applied Physiology Laboratory at the University of Mississippi, where he focuses his research on skeletal muscle adaptations to exercise in combination with blood flow restriction (BFR). In this episode, Jeremy explains the science of BFR and the mechanisms by which BFR training can produce hypertrophy using low loads. Here, he reviews anatomy and terminology of muscle structure and discusses the evidence that increasing muscular strength may not be dependent on increasing muscle size. Additionally, Jeremy goes into depth on how one might take advantage of BFR training, including practical applications for athletes and average people, as well as the situations for which BFR training would be most advantageous. We discuss:
Jeremy’s interest in exercise and weightlifting and his scientific training [3:30];
The microstructure and physiology of muscle [8:00];
Definitions of fast-twitch and slow-twitch muscle fibers [12:45];
Comparison of strength vs. hypertrophy [21:30];
Blood flow restriction training and the origins of the Kaatsu system [28:30];
The details and metrics related to exercise under blood flow restriction [44:45];
Considerations when training with blood flow restriction: loading, pace, rest, and risks [53:00];
Blood flow restriction studies and the relationship between muscle size and muscle strength [1:04:15];
Evidence that increasing muscular strength is not dependent on increasing the size of the muscle [1:16:30];
Practical applications of blood flow restriction training for athletes and average people [1:27:30];
Situations in which blood flow restriction training is most advantageous [1:35:30];
The mechanisms by which blood flow restriction training can produce so much hypertrophy at such low loads [1:39:45];
Applications of “passive” blood flow restriction training [1:47:15];
What experiments would Jeremy do if he had unlimited resources? [1:51:45];
