Muscle fibers need to have an increased tension applied to them to increase their size or muscle hypertrophy. This also translates into increased strength, directly. In our clinic, we try to aim for about 80% of 1 repetition maximum when selecting the amount of resistance a patient is to lift. However, in most cases, this is impossible since the patients come with injuries to the joint, ligament, nerve or muscles that prevent them from this much increase in resistance. However, with the use of the Blood Flow Restriction Training (BFR) this is possible. In a study by Takarada,(2004) low intensity exercises with BFR were compared to low intensity exercises without BFR. To clarify, low intensity means using only 20% to 30% of 1 repetition maximum. The results in muscle cross sectional area were larger in the group that had the BFR applied vs the one that did not. The knee extensions were 10.3 +/- 1.6 % bigger, and 9.3 +/- 2.2 % stronger in the group with BFR. The other group had no change in size and near 3% increase in strength. Other studies compared High Intensity training (HIT 80% 1 RM), low intensity BFR (30% 1 RM) and low intensity without BFR (30% 1 RM). Only the HIT and BFR groups had significant increments in strength and cross sectional area of the muscle or hypertrophy. In some cases, the BFR group had a significantly larger hypertrophy in muscles than the HIT group.
The current mechanism through which muscle hypertrophy and strength are obtained are unknown when using the BFR. However, there are several theories that are proposed to explain these physiological changes: increased fiber type recruitment, metabolic accumulation, activation of muscle protein synthesis, and cell swelling.
This information was obtained from Owens Recovery Science. Dr. Santiago Osorio, PT, DPT, OCS is certified Owens Recovery Science in the use of BFR.