Electrical stimulation-evoked resistance exercise therapy improves arterial health after chronic spinal cord injury

Abstract

Study design: Repeated measures training intervention.

Objectives: To evaluate the effects of neuromuscular electrical stimulation (NMES)-induced resistance exercise therapy on lower extremity arterial health in individuals with chronic, complete spinal cord injury (SCI). We define "arterial health" using three surrogate markers: (a) resting diameter, (b) flow-mediated dilation (FMD), and (c) arterial range.

Setting: Department of Kinesiology, University of Georgia, USA.

Methods: We assessed five 36+/-5-year-old male individuals with chronic, complete SCI before, during, and after 18 weeks of training. The quadriceps femoris muscle group of both legs were trained twice a week with 4 x 10 repetitions of unilateral, dynamic knee extensions. The health of the posterior tibial artery was assessed using a B-mode ultrasound unit equipped with a high-resolution video capture device. Proximal occlusion was used to evoke ischemia for 5 min and then for 10 min. FMD was calculated using the peak diameter change (above rest) following 5 min occlusion. Arterial range was calculated using minimum (during occlusion) and maximum diameters (post 10 min occlusion). Hierarchical linear modeling accounted for the nested (repeated measures) experimental design.

Results: FMD improved from 0.08+/-0.11 mm (2.7%) to 0.18+/-0.15 mm (6.6%) (P=0.004), and arterial range improved from 0.36+/-0.28 to 0.94+/-0.40 mm (P=0.001), after 18 weeks of training. Resting diameter did not significantly change.

Conclusions: Home-based, self-administered NMES resistance exercise therapy consisting of 80 contractions/week improved FMD and arterial range. This provides evidence that resistance exercise therapy can improve arterial health after SCI, which may reduce the risk of future cardiovascular disease.