The Effect of Low-Load Blood Flow Restricted Exercise Training on Voluntary Muscle Activation: Implications for Rehabilitation

The purpose of this study was to investigate the effects of short-term LL-BFRT on the level of voluntary neuromuscular activation of the quadriceps femoris (QF) muscle in people with knee joint impairments.

33 orthopaedic patients with QF weakness (ACL deficiency, patellofemoral pain syndrome) and 12 healthy subjects (control group) of both sexes participated. Over a period of 4 weeks, the participants completed 12 training sessions, 3 times per week, with each session consisting of 4 sets of unilateral leg press and knee extension. The LL-BFRT group (n = 16) and the control group exercised with restricted blood flow (cuff pressure 120-140 mmHg), while the sham LL-BFRT group (n = 17) exercised with apparently restricted blood flow (cuff pressure 20 mmHg). Mean differences were analysed with a 2 × 2 (time × group) factorial ANOVA for repeated measures on one factor. The study was approved by the Medical Ethics Committee of the Republic of Slovenia (No. 0120-496/2018/8) and was conducted in accordance with the Declaration of Helsinki and the Oviedo Convention.

There was no significant interaction between the factors time and group for maximal voluntary isometric contraction (MVIC) torque, time of sustained isometric contraction at 60% MVIC torque and level of voluntary activation (interpolated twitch technique). After the intervention (time factor), the level of voluntary muscle activation increased by 7.6 % (p = 0.039) in the LL-BFRT group and by 4.4 % (p = 0.037) in the control group. The MVIC torque increased by 7.2 % in the LL-BFRT group (p = 0.041) and by 11.8 % in the sham LL-BFRT group (p = 0.006). Isometric muscle endurance only increased in the control group by 15.4 % (p = 0.047).

Short-term LL-BFRT does not appear to increase the level of voluntary QF activation and strength in patients with knee pain more than standard low-load resistance training. The relatively small number of subjects included and their wide variability in response to treatment do not allow a clear conclusion in this regard. Future studies with more homogeneous groups of patients with knee impairment are needed.

Although treatment of QF muscle weakness with LL-BFRT did not significantly enhance the training effect in a specific cohort of subjects, the observed trend towards an enhanced increase in the level of voluntary neuromuscular activation warrants further investigation.