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 d·wk−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°·s−1 and +8.3% at 180°·s−1) voluntary contractions. In addition, maximal isometric strength decreased (−6.8%), whereas no large fall (−1.9% at 90°·s−1 and −0.6% at 180°·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.