Effect of Low-Frequency Neuromuscular Electrical Stimulation Combined with Passive Cycle-ergometry on hemodynamics in Healthy Adults

Background: There have been few studies that have examined hemodynamic responses to Low-frequency neuromuscular electrical stimulation (LF-NMES), and the effects of combining passive cycle-ergometry are still unclear. The purpose of this study was to examine the effects of a combination of LF-NMES and passive cycle-ergometry on hemodynamic responses with a primary focus on the Fick principle in healthy adults.

Methods: A randomized, crossover trial was conducted to evaluate the responses to three types of supine exercises (LF-NMES alone, LF-NMES with passive cycle-ergometry, and voluntary cycle-ergometry) adjusted to the same exercise intensity as the oxygen consumption of 14 mL/kg/min in 13 healthy adult men. Blood pressure, heart rate, blood lactate concentration, stroke volume (SV), cardiac output (CO), and left ventricular end-diastolic volume (LVEDV) were measured during each exercise in all subjects. The arterial-venous oxygenation difference (A-VO₂ difference) was calculated based on Fick's equation.

Results: LVEDV, SV, and CO were lower, and the A-VO₂ difference and blood lactate concentration were higher in LF-NMES alone than in voluntary cycle-ergometry and LF-NMES with passive cycle-ergometry (p<0.05, respectively). The blood lactate concentration was lower in LF-NMES with passive cycle-ergometry than in LF-NMES alone, but slightly higher than in voluntary cycle-ergometry (p<0.05, respectively).

Conclusion: Hemodynamic and metabolic responses of exercise with LF-NMES alone seemed consistent with insufficient peripheral perfusion based on the elevation of A-VO₂ difference and blood lactate concentration. The findings suggest that combining passive cycle-ergometry with LF-NMES improves the insufficient peripheral perfusion induced by LF-NMES alone.