The Effect Of Multiple Muscle Stimulation On Lower-body Metabolic Rate And Blood Flow

BACKGROUND: Neuromuscular electrical stimulation (NMES) may provide similar health benefits to those seen with voluntary exercise. PURPOSE: The purpose of this project was to evaluate acute changes in whole-body metabolism, local muscle metabolism, and arterial blood flow in response to NMES of eight muscle groups in the legs of healthy, college-aged volunteers. METHODS: For each participant, measurements were assessed once at rest, twice during stimulation (5- & 10-min.), and once following NMES. Stimulation was set to a frequency of 5 Hz, with currents producing vigorous, submaximal contractions. The muscles stimulated included the vastus lateralis, biceps femoris, tibialis anterior, and the medial gastrocnemius of both legs. Data were collected over three sessions. In the first session, arterial occlusion using a pressure-supplied cuff was combined with near-infrared spectroscopy (NIRS) to measure the rate of muscle oxygen consumption. For the second session, whole-body oxygen consumption was assessed via a metabolic cart. During the final session, femoral arterial blood flow was measured using Doppler ultrasound technology. Significance (*) when p < 0.05. RESULTS: Group average results (n = 5) are detailed below (means and SD). - Heart Rate (BPM) Whole-Body Metabolism (VO2) Local-Muscle Metabolic Rate (O2Hb/s) Peak Sys Blood Velocity (cm/s) Peak Dia Blood Velocity (cm/s) Femoral Artery Diameter (cm) Resting 70.5 ± 11.3 3.8 ± 0.7 5.5 ± 4.9 102.5 ± 28.4 -36.1 ± 12.9 0.58 ± 0.11 5-Min of Stimulation - 3.77 ± 0.66 30.1 ± 18.4 * 126.8 ± 53.1 -27.0 ± 21.9 0.58 ± 0.11 10-Min of Stimulation 83.0 ± 17.6 * 5.3 ± 1.3 * 69.1 ± 68.9 115.3 ± 55.9 -17.4 ± 18.6 * 0.59 ± 0.10 Post- Stimulation 71.0 ± 12.7 4.5 ± 1.0 * 24.4 ± 17.8 98.3 ± 33.6 -33.0 ± 33.6 0.57 ± 0.10 CONCLUSIONS: NMES stimulation of eight lower-body muscles produced small but significant increases in local muscle metabolic rate during stimulation, associated with increases in metabolism and arterial blood flow. Higher stimulation levels may produce greater metabolic and blood flow increases; however, such currents were avoided to ensure participant comfort. The resulting submaximal, multiple muscle NMES may, however, still be beneficial for individuals with severely low levels of physical activity.