How Blood Flow Restriction (BFR) Training Works
The idea for blood flow restriction or BFR training originated in Japan during the 1960’s when a young man who was kneeling at a Buddhist temple felt his calves become numb. After much experimentation, figuring out how this happens and the best way to reproduce it in a controlled manner, ‘Kaatsu’ training began to be practiced in the 1970’s.
The basis of occlusion training, as it is now known in the western world, is that we are aiming to minimise the venous outflow from a muscle, while also reducing the arterial inflow (shown in early studies by Takarada et al., 2000, and Takarada et al., 2002). Subsequently what happens is that we get changes in:
- muscle oxygenation
- fibre type recruitment
- metabolic accumulation
- growth hormone response
- stimulation of protein synthesis
- muscle growth inhibitors
These processes are reviewed in detail in a paper published in 2013 by Zachary Pope, Jeffrey Willardson, and Brad Schoenfeld, titled Exercise and Blood Flow Restriction and in the work of the lead researcher in the area Jeremy P. Loenneke who has published numerous studies on the topic of occlusion training.
When the blood flow is occluded lactate accumulates, increasing metabolic demand and stimulating many physiological responses (as well as making you feel like you’re constantly in the middle of an anaerobic training session!).
With the reduced oxygen supply to the muscles we can’t recruit as many Type 1, slow twitch fibres as they rely on oxygen to contract. As a result we get earlier activation of the Type 2 (x-II), fast twitch fibres that are anaerobically driven. These fibres characteristically produce high forces and display hypertrophy. So we have a scenario where the occlusion training is targeting the muscles that are most likely to increase strength and size. Also, they fatigue quicker, so you feel tired. Very tired.
Growth hormone is also stimulated to levels far beyond that of regular exercise, with studies showing 200-300% increases in the involved muscles with occlusion training.
Protein synthesis is an essential muscular response to training that stimulates growth and development. Blood flow occlusion when exercise training has been shown to result in over 50% more muscle protein synthesis than a traditional exercise-training program. This protein synthesis response was observed to be elevated for up to three hours post occlusion training.
When we exercise some genes (e.g. myostatin) are expressed that regulate overgrowth of muscles, and so can be inhibitory to hypertrophy. The evidence shows that blood flow occlusion can reduce the expression of myostatin, possibly by reducing the information returning to the genes, subsequently causing better muscle development.
The American College of Sports Medicine (ACSM) guidelines state that loads of at least 70% of an individual’s 1-repetition maximum are needed to stimulate muscle hypertrophy. However, when occluding blood-flow, loads as low as 20% can stimulate muscle growth and hypertrophy. This has huge potential benefit with rehabilitation, as typically we have to perform exercise with much lighter loads when injured. This benefit is particularly relevant for post-operative patients, for whom minimising muscle wastage (atrophy) is a priority. Additionally, research has found that occlusion training can increase cardiorespiratory endurance in shorter durations than traditional exercise, and local muscular endurance.
With hundreds of academic papers published on the topic of occlusion training this description only serves as an introduction to the physiological effects and benefits of occlusion training. The level of detail that could be delved into would have made this post a thesis had we discussed everything. So we will discuss each point in the detail it deserves in the next while.
There has also been a particularly busy flurry of recently published articles looking at a variety of applications for occlusion training. This means a lot of reading to do in order to keep up with what is a rapidly progressing phenomenon.