Training-induced changes in muscle contraction patterns enhance exercise performance after short-term neuromuscular electrical stimulation

BACKGROUND: Neuromuscular electrical stimulation (NMES) is a complementary tool for therapeutic exercise for muscle strengthening and may potentially enhance exercise performance. OBJECTIVE: To determine whether high-intensity interval training (HIIT) and continuous aerobic training (CA) coupled with NMES enhance the changes in the eccentric/concentric muscle contraction patterns of hamstring and quadriceps. METHODS: Forty-five healthy sedentary male participants performed cycling training 3 times per week for 8 weeks combined with/without NMES performed at a load equivalent to 65% and 120% of IVO2max (intensity associated with the achievement of maximal oxygen uptake). Anthropometrics, blood lactate measurements, IVO2max, TLimVO2max (time-to-exhaustion) and isokinetic strength parameters were measured at baseline and post-training using a randomized controlled trial. RESULTS: The conventional hamstring-to-quadriceps-ratio (HQR: Hcon/Qcon) at 60 degrees/s and the Dynamic Control Ratio (DCR: Hecc/Qcon) at 180 degrees/s significantly increased both in the dominant (D) and non-dominant (ND) limb in the HIIT + NMES group (p < 0.05). There was a positive significant correlation between the individual changes in D HQR at 60 degrees/s and IVO2max (r = 0.94, p = 0.005) and the DCR at 180 degrees/s and TLimVO2max (r = 0.90, p = 0.015), respectively. CONCLUSIONS: The increases in the eccentric muscle contraction and DCR following HIIT + NMES seem to improve fatigue tolerance, cause less fatigue and oxidative stress on the lower limb during pedaling at high intensities.