Effect Of Neuromuscular Electrical Stimulation With Blood Flow Restriction On Muscle Size And Strength

Low load voluntary exercise can induce muscle hypertrophy and strength gain when combined with blood flow restriction (BFR). However, it is unknown whether muscle hypertrophy and strength gain can be induced by involuntary muscle contractions via low intensity neuromuscular electrical stimulation (NMES) combined with BFR. PURPOSE: To investigate the effects of low intensity NMES training combined with BFR on muscles hypertrophy and strength gain. METHODS: Eight untrained young men (age: 26.2±0.7 yrs, height: 1.74±0.02 m, body mass: 71.4±14.5 kg) received 23 minutes of unilateral very low-intensity (5-10 % of maximal voluntary contraction) NMES, twice a day, 5 days per week, for 2 weeks, with one leg combined with BFR (NMES-BFR) and the other receiving NMES only (NMES-CON). Knee extensors were stimulated at a fixed knee joint angle of 75°. After that, subjects completed 2 weeks of detraining. A nylon cuff with a width of 105 mm was applied tightly at the most proximal portion of the NMES-BFR leg. Subjects received four sets of BFR for 5 min with 1 min of rest between sets. The mean pressure was 158±6 mmHg. The quadriceps muscles thickness (MT) and isometric and isokinetic strength were measured before and every week throughout the training and detraining period. RESULTS: Two way repeated measures ANOVA revealed a significant main effect of time (p<0.001) and condition × time interaction (p<0.001), illustrating that MT increased (3.9%) after 2 weeks of training programs, which then decreased to the basal level (-3.0%) after 2 weeks of the detraining period in NMES-BFR. With regard to muscle strength, a main effect of time and condition × time interaction were significant (p<0.05) for all angular velocities. Specifically, NMES-BFR increased maximal knee extension strength under isometric (+14.2%) and isokinetic (+7.0% at 90°/s, +8.3% at 180°/s) conditions after the 2 weeks training period. In addition, isometric maximal strength decreased (-6.8%), whereas a large decrease in isokinetic maximal strength was not observed (-1.9% at 90°/s, -0.6% at 180°/s) after the 2 weeks detraining period. Meanwhile, NMES-CON showed no effect except for a negligible effect on isometric strength. CONCLUSIONS: Low intensity NMES combined with BFR can induce muscle hypertrophy and strength gain in untrained young men.