Many people wonder how blood flow restriction can be so effective at loads as light as 20-40% 1 RM in producing similar gains in muscle mass and (to a lesser extent) strength as heavier load (60-70+% 1RM) protocols.

It all comes down to understanding three main concepts: the force-velocity (FV) curve, fatigue and the effect of fatigue on muscle activation patterns.

As we introduce our blog to the fitness and rehab community, the BFR Pros is excited to announce that our inaugural blog posts will be focused on breaking down the science behind blood flow restriction. 

Concept 1: The Force-Velocity Curve

The Force Velocity Curve

The Force-Velocity Curve describes how much force a muscle fiber can generate at different shortening speeds. The caveat here is that it only describes maximum effort attempts during a concentric muscle contraction. Under this lens, low-load training (under 50% 1 RM) is ineffective at building muscle mass because the muscle force per muscle fiber at very fast speeds is minimal. When a muscle fiber is able to produce significant force through adequate tension (mechanical tension) from the load, mechanotransduction occurs and muscle protein synthesis shortly follows. Although in the case of a very fast muscle muscle contraction, the muscle fiber is not producing high levels of force and as a result, negligible muscle protein synthesis signaling. However, when lifting heavy weights (> 70% 1RM), it’s very difficult to lift the weight very fast even with very high amounts of intent/effort. This leads to high levels of muscle force and strong stimulation of muscle protein synthesis that will promote muscle growth (along with a good nutrition plan surrounding the workout).

Want to learn more about the science behind BFR? Check out our blog archives, where we break down the other 2 concepts behind the effectiveness of Blood Flow Restriction.

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