Resistance Training Increases Fatigue Resistance But Not Artery Size Or Function In Individuals With SCI

Abstract

PURPOSE The purpose of this study was to evaluate the effect of lower extremity resistance-training on quadriceps fatigability, femoral artery diameter, and femoral artery blood flow. METHODS Five male chronic SCI individuals (ASIA A complete; C5 - T10; 36 +/− 5 yrs old) completed 18 weeks of home-based neuromuscular electrical stimulation (NMES) resistance training. Subjects trained the quadriceps muscle group twice a week with 4 sets of 10 dynamic knee extensions against resistance while in a seated position. Ultrasound was used to measure femoral artery diameter and blood flow. Blood flow was measured before, during, and after 5 and 10 minutes of distal cuff occlusion. A 4-minute isometric electrical stimulation protocol was also completed. All measurements were made before training and after 8, 12, and 18 weeks of training. RESULTS Training resulted in significant increases in weight lifted and muscle mass, as well as a 60% reduction in muscle fatigue (P=0.001). However, femoral arterial diameter did not increase. The range was 0.44±0.03 cm to 0.46±0.05 cm over the 4 time points (P=0.70). Resting, reactive hyperemic, and exercise blood flow did not appear to change with training. CONCLUSIONS NMES resistance training improved muscle size and fatigue despite an absence of response in the supplying vasculature. These results suggest that the decreases in arterial caliber and blood flow seen with SCI are not tightly linked to muscle mass and fatigue resistance. In addition, muscle fatigue in SCI patients can be improved without increases in arterial diameter or blood flow capacity. SPONSORSHIP: Grants HL65179, HD39676, and HD39676S2.