Effects of Electrostimulation with Blood Flow Restriction on Muscle Size and Strength

Purpose: Low-load voluntary exercise can induce muscle hypertrophy and strength gain in working muscles when combined with blood flow restriction ( BFR). However, it is unknown whether such hypertrophy and strength gain can be induced by involuntary muscle contractions triggered via low- intensity neuromuscular electrical stimulation ( NMES) combined with BFR. The purpose of this article was to investigate whether low- intensity NMES combined with BFR ( NMES- BFR) could elicit muscle hypertrophy and strength gain in the quadriceps. Methods: Eight untrained young male participants ( mean +/- SE; age, 26.2 +/- 0.7 yr; height, 1.74 +/- 0.02 m; body weight, 71.4 +/- 4.8 kg) were subjected to 23 min of unilateral low- intensity ( 5%- 10% of maximal voluntary contraction) NMES twice per day ( 5 dwk -1) for 2 wk: one leg received NMES- BFR and the other leg received NMES alone. Quadriceps muscle thickness and isometric and isokinetic strength were measured before and every week throughout the training and detraining periods. Results: In NMES- BFR legs, muscle thickness increased after 2 wk of training (+ 3.9%) and decreased after 2 wk of detraining ( -3.0%). NMES- BFR training also increased maximal knee extension strength in isometric (+ 14.2%) and isokinetic (+ 7.0% at 90 degrees s(-1) and + 8.3% at 180 degrees s(-1)) voluntary contractions. In addition, maximal isometric strength decreased ( -6.8%), whereas no large fall ( -1.9% at 90 degrees s(-1) and -0.6% at 180 degrees s(-1)) in isokinetic maximal strength was evident after 2 wk of detraining. In legs that received NMES alone, no prominent change was observed; there was a negligible effect on isometric strength. Conclusion: Low-intensity NMES- BFR induces muscle hypertrophy and strength gain in untrained young male participants.