How blood flow restriction training builds muscle with light weights.

The cuff sits at the top of the limb and inflates to a pressure that partly restricts the arteries bringing blood in, and more fully restricts the veins carrying it out. The muscle below becomes a low-oxygen environment within one set. The 2019 position stand sets the pressure at 40 to 80 percent of your arterial occlusion pressure, the pressure at which flow into that limb would stop, so the number is personal to your limb rather than fixed.

Light weights are normally handled by slow, oxygen-dependent muscle fibres, and the fast fibres that grow most are never asked to work. Under the cuff the slow fibres run out of oxygen and fail, so the nervous system recruits the fast fibres to keep the movement going. The 2015 review by Pearson and Hussain lists that recruitment, plus the build-up of by-products in the trapped blood and swelling of the muscle cells, as the main reasons BFR produces growth at loads under 50 percent of maximum.

Because BFR grew up in research labs, the protocol is well defined. Your physiotherapist adapts it to your injury and your response.

The position stand links numbness and excess soreness to pressures set outside the guidelines, which is what a strap pulled tight by feel produces. In a 2024 survey of 397 practitioners, 81.1 percent set pressure from occlusion pressure and 68.2 percent screen for contraindications first. At Launch Rehab, BFR runs inside a physiotherapy visit at New Westminster with cuffs that calibrate to your limb.