Abstract
This study compared electromyographic (EMG) amplitude, the number of repetitions completed, and exercise volume during three sets to failure of high- (80% 1RM) versus low-load (30% 1RM) forearm flexion resistance exercise on a subject-by-subject basis. Fifteen men were familiarized, completed forearm flexion 1RM testing. Forty-eight to 72 h later, the subjects completed three sets to failure of dumbbell forearm flexion resistance exercise with 80% (n = 8) or 30% (n = 7) 1RM. EMG amplitude was calculated for every repetition, and the number of repetitions performed and exercise volume were recorded. During sets 1, 2, and 3, one of eight subjects in the 80% 1RM group demonstrated a significant linear relationship for EMG amplitude versus repetition. For the 30% 1RM group, seven, five, and four of seven subjects demonstrated significant linear relationships during sets 1, 2, and 3, respectively. The mean EMG amplitude responses show that the fatigue-induced increases in EMG amplitude for the 30% 1RM group and no change in EMG amplitude for the 80% 1RM group resulted in similar levels of muscle activation in both groups. The numbers of repetitions completed were comparatively greater, while exercise volumes were similar in the 30% versus 80% 1RM group. Our results, in conjunction with those of previous studies in the leg extensors, suggest that there may be muscle specific differences in the responses to high- versus low-load exercise.
Highlights
The current American College of Sports Medicine [1] and National Strength and ConditioningAssociation [2] guidelines recommend the utilization of resistance exercise loads corresponding to60%–80% and 67%–85% of one repetition maximum (1RM), respectively, to maximize muscle hypertrophy
The individual EMG amplitude versus repetition responses in our study indicated that muscle activation increased linearly for all subjects in the 30% 1RM group during set 1
The results of the present study indicated that forearm flexion resistance exercise to failure at 30% 1RM caused fatigue-induced increases in EMG amplitude, whereas during 80% 1RM, EMG
Summary
The current American College of Sports Medicine [1] and National Strength and ConditioningAssociation [2] guidelines recommend the utilization of resistance exercise loads corresponding to60%–80% and 67%–85% of one repetition maximum (1RM), respectively, to maximize muscle hypertrophy. Burd et al [3] demonstrated that acute resistance exercise performed to failure at 30% 1RM resulted in similar magnitudes of muscle protein synthesis and anabolic signaling as resistance exercise at 90% 1RM. In a follow-up study, Mitchell et al [4] demonstrated that 10 weeks of leg extension resistance training to failure at 80% 1RM versus 30% 1RM resulted in comparable muscle hypertrophy. Ogasawara et al [5] showed that six weeks of bench press resistance training at 80% 1RM caused muscle hypertrophy equivalent to that observed after training at 30% 1RM. The disparity between current resistance training recommendations and recent experimental results [3,4,5] has sparked a debate [6,7] regarding the most effective loads to prescribe to enhance muscle size with resistance training
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