The influence of low-intensity resistance training combined with neuromuscular electrical stimulation on autonomic activity in healthy adults: A randomized controlled cross-over trial

Background: Low-intensity resistance training (RT) combined with neuromuscular electrical stimulation (NMES) is one method of exercise to improve the deterioration of physical function. However, it is unclear whether low-intensity RT combined with NMES (RT + NMES) can be safely implemented. Objective: This study aimed to examine the influence of low-intensity RT + NMES on autonomic activity and cardiovascular responses in healthy adults. Methods: This study was an open-label, randomized controlled cross-over trial. The exercise intensity of isometric knee extension RT was set to 40% of the maximum voluntary contraction (peak torque). NMES was adjusted to a biphasic asymmetrical waveform with the frequency maintained at 50 Hz and a phase duration of 300 mu s. The difference in the change in autonomic activity and cardiovascular responses was compared by assessing heart rate variability, blood pressure, and heart rate during RT and RT + NMES. Results: Twenty healthy male college students (mean age 21.0 +/- 0.6 years) participated in this study. The ratio of low- and high-frequency components of heart rate variability, systolic blood pressure, and heart rate increased during exercise in the RT and RT + NMES sessions (P < 0.05). There were no significant differences in autonomic activity and cardiovascular responses throughout the sessions during RT and RT + NMES. Conclusion: In conclusion, our results demonstrated that low-intensity RT + NMES was safe and did not induce excessive autonomic and cardiovascular responses in healthy adults.