Effects of low-load resistance training with blood flow restriction on muscle size and strength of professional soccer players with muscle imbalance

The purposes of this study were to determine whether low intensity resistance training combined with blood flow restriction (LI-BFR) could affect the concentric hamstrings/quadriceps muscle strength ratio (Hcon:Qcon) of professional soccer players with Hcon:Qcon imbalance (Study 1), and whether hamstrings strength response observed after LI-BFR is associated with muscle hypertrophy (Study 2). In the Study 1, athletes were randomly divided into a training group (n = 6) and a control group (n = 5). In the Study 2, all athletes (n = 11) have performed the training programme. The athletes participated in a 6-week (twice a week) supervised training programme (unilateral knee flexion at 30% 1RM) consisting of 12 training sessions. Peak concentric torque of knee flexors (+8%; P < 0.001) and Hcon:Qcon (+9%; P < 0.01) were significantly increased after LI-BFR. Moreover, the cross sectional area (CSA) of the hamstrings was significantly increased (+10%; P < 0.001) after LI-BFR. Thus, the addition of hamstrings strength training programme using LI-BFR during preseason is able to enhance both Hcon:Qcon and hamstrings CSA of professional soccer players with Hcon:Qcon imbalance.