Electromyography and high-speed elbow flexor exercise

Our study assessed motor unit behavior and muscle function from high-speed unilateral elbow flexor workouts. Electromyography and performance data were obtained from subjects who completed three workouts on an Impulse (Impulse Training Systems; Newnan, GA) exercise machine. Comprised of both tonic and phasic repetitions, workouts were done with three different loads (1.13, 3.4 and 6.8 kg) added to the machine. Electromyography was measured from three muscles (biceps brachii, triceps brachii, brachioradialis). Dependent variable means, obtained as the elbow flexed and extended, were compared with 2 (tonic, phasic) x2 (men, women) x3 (1.13, 3.4 and 6.8 kg) ANOVAs, with repeated measures for repetition and load. Bonferroni's adjustment preserved family-wise error rates and t-tests served as a post-hoc. With α=0.05, several dependent variables displayed intra-repetition and -load effects. However triceps root mean square (RMS) values displayed repetition x load interactions for both elbow flexion and extension. The triceps, an elbow flexion antagonist, may act as an important joint stabilizer, particularly at faster velocities and more extended joint angles. Unlike isometric or standard low-velocity paradigms performed against heavy loads, high-speed exercise may entail a more equitable distribution among factors (motor unit recruitment, rate coding, reflex potentiation, antagonist co-contraction) responsible for current triceps RMS values.