Optimization of Protocols Using Neuromuscular Electrical Stimulation for Paralyzed Lower-Limb Muscles to Increase Energy Expenditure in People With Spinal Cord Injury

Objective The aim of this study was to evaluate whether using surface neuromuscular electrical stimulation (NMES) for paralyzed lower-limb muscles results in an increase in energy expenditure and whether the number of activated muscles and duty cycle affect the potential increase. Design This was a cross-sectional study. Results Energy expenditure during all NMES protocols was significantly higher than the condition without NMES (1.2 ± 0.2 kcal/min), with the highest increase (+51%; +0.7 kcal/min, 95% confidence interval, 0.3-1.2) for the protocol with more muscles activated and the duty cycle with a shorter rest period. A significant decrease in muscle contraction size during NMES was found with a longer stimulation time, more muscles activated, or the duty cycle with a shorter rest period. Conclusion Using NMES for paralyzed lower-limb muscles can significantly increase energy expenditure compared with sitting without NMES, with the highest increase for the protocol with more muscles activated and the duty cycle with a shorter rest period. Muscle fatigue occurred significantly with the more intense NMES protocols, which might cause a lower energy expenditure in a longer protocol. Future studies should further optimize the NMES parameters and investigate the long-term effects of NMES on weight management in people with SCI.