Blood Flow Restriction (BFR)

What is BFR ? 

Blood Flow Restriction (BFR) is a training technique that combines low-intensity loading with occlusion of blood flow to achieve the same results as high-intensity training. BFR modifies acute physiological stressors such as local oxygen availability in the muscle and vascular shear stress, which can lead to adaptations not easily achieved with conventional training (1). This technique can be used in rehabilitation but also in injury prevention by allowing the athlete to better withstand the training loads. Indeed, the weights lifted are much lower than usual, thus reducing the stress on the joints without reducing the effectiveness of the training. In addition, BFR has contributed greatly to the physiological understanding of muscle fatigue, blood pressure reflexes and metabolism in humans (1).

And what does it do ? 

Effects : 

• Rapid increases in muscle size, strength and endurance capacity even with lower intensity and resistance!
• Improves power and speed of change of direction by increasing the maximum ability to produce force against an external object. The development of this muscle strength can influence the economy of submaximal movements and the potential for explosive movements, such as sprinting and jumping (2)
• Increased daily myofibrillar protein synthesis from the first BFR session. This adaptation increases the number of contractile units in the muscle.
• It is possible that some neural adaptations occur to improve the ability to generate muscle power (1). Thus better muscle activation could be induced during exercise although this is difficult to prove at the moment. 

Physiologically what is actually happening ? 

When exercise is combined with BFR, the availability of essential substrates such as oxygen or extracellular fuel sources usually carried by the blood will be reduced. Thus, the body will be forced to turn to local substrates such as glycogen or phosphocreatine to produce ATP, which are sources of metabolic energy for the body. These changes in the supply of energy substrates could increase physiological stress, and thus potentiate mitochondrial adaptations (1). Indeed, Egan et al (3) proved that, depending on the constraints of the environment in which the muscle was located, the mitochondria and their oxygenation capacities could evolve and above all adapt. Groennebaek et al (4) provided physiological evidence for these adaptations in our organism. Following their study, it was possible to observe that in 6 weeks of low load resistance training combined with BFR, muscle mitochondrial protein synthesis and respiratory capacity increased in a similar way to the changes observed after high load resistance training. Thus, it is possible to achieve the same effects while decreasing the training load. However, further research into mitochondrial adaptations and their precise role in the development of physical capacity seems essential. 

To qualify this, it is essential to consider the cardiorespiratory system, which is fundamental to substrate delivery, waste disposal and whole-body regulatory processes (e.g. acid-base balance and thermoregulation). Structural changes within the heart are known to take months to years of training (5), leaving the primary mechanism of short-term BFR training in doubt. Thus it is still important to take a step back from these techniques in order to use them wisely and not just try to achieve results on cardiorespiratory parameters. 

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