Electromyographic Analysis of Suspension Elbow Flexion Curls and Standard Elbow Flexion Curls

Abstract

Anecdotal claims state that the TRX suspension trainer increases muscle recruitment compared to standard modes of training. Despite these claims, a comparison of muscle activation between standard free weight exercise and TRX suspension training has not been previously examined. PURPOSE: To compare muscle recruitment during a suspended standing elbow flexion curl and a standard standing elbow flexion curl at a moderate (50% 1RM) and heavy (75% 1RM) resistance load. METHODS: Seven college aged (24 ± 2.6 yrs; ± SD) students (4 males and 3 females) participated in this study. The resistance for the TRX suspension and standard flexion curl corresponded to 50% and 75% 1RM for a standardized preacher curl. Recruitment of the targeted muscle groups (medial biceps brachii, lateral biceps brachii, anterior deltoid, trapezius, and lower rectus abdominus) was recorded using surface electromyography (sEMG). All sEMG recordings were obtained on the same day; the order of contraction intensity and exercise mode was randomized between subjects. Each subject performed 5 contractions at a controlled duty cycle of 2 s concentric, 2 s eccentric, 4 s rest period for each intensity and exercise mode. sEMG was analyzed by averaging the rectified and integrated EMG signal determined for each contraction. Prior to data collection, subjects performed three familiarization workouts on the TRX suspension system and standard curls to minimize learning effects. RESULTS: The measured resistance was similar for TRX suspension and standard flexion curl at both 50% (16.4 ± 7.1 kg)and 75% (24.7 ± 10.7 kg)1RM. Compared to the standard flexion curl, the anterior deltoid exhibited greater (p<0.05) activation during TRX suspended elbow flexion curl at both 50% and 75% 1RM. There was no difference in muscle activation between exercise modes or as a function of contraction intensity for the other muscles examined. CONCLUSIONS: Greater activation of the anterior deltoid was likely due to the greater shoulder flexion that is required throughout the range of motion during TRX suspension exercise. Further detailed investigations are required to determine if differences in muscle activation occur during the concentric, eccentric or rest phase between TRX suspension exercise and standard free weight exercise.