The principle of training specificity states that muscle will adapt to the specific demands placed on it. Blood flow restricted training (BFR) places specific demands on muscle tissue such as high metabolic stress and high momentary muscle fatigue. One would expect that this type of training would result in significant increases in muscle strength and/or strength endurance.
The University of Southern Denmark took 20 subjects and split them into two groups; one group performed 20 workouts of leg extensions (four sets to failure at 20% 1RM) with BFR over the course of 19 days while the other group performed the same workout with the same amount of weight and reps but without BFR. Strength and muscle biopsies were taken before, during, and five and 12 days after training had stopped.
Gains in rapid muscle force-generating capacity and strength were not manifested before 12 days after all training had stopped. The group that didn’t use blood flow restriction experienced no changes at all.
Blood flow–restricted exercise produces substantial metabolic stress which reduces muscle contractile capacity for an extended period (days to weeks) resulting in delayed manifestation of strength gains after training has stopped.
This study had subjects perform BFR training every weekday, twice per day. This led to prolonged decrements in strength and delayed strength gains for nearly two weeks after training stopped. If incorporating BFR into your routine, leave sufficient recovery time between BFR sessions and if strength becomes stagnant or even declines, discontinue BFR training for a couple weeks.