Effects of High and Low Intensity Weight Training on iEMG and Force 1139

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To test the hypothesis that the EMG to Force relationship is a function of training intensity, thirteen weight trained college-age males were divided into two groups for 8 weeks of periodized training on the bench press. Prior to the study, subjects trained regularly for at least 1 year on the bench press. Subjects performed two 1RM tests separated by 48-96 hours for the pretest and posttest. After the pretest, subjects were assigned to either a High Repetition (HiRep) or Low Repetition (LoRep) group. There were no pretest differences in 1RM between groups. Subjects trained twice per week with 3-4 sets. HiRep trained at 10RM to 15RM per set while LoRep trained at 6RM to 2RM per set. Pretest and posttest EMG was measured on the lateral head of the triceps, the anterior deltoid and the pectoralis major. EMG was rectified, filtered and integrated. The iEMG was adjusted for the duration of the 1RM and averaged across the 3 muscles. A repeated measures ANOVA showed similar increases (p<.05) in 1RM for LoRep (112.9 ± 6.53 kg to 117.0± 7.07 kg) and HiRep (107.7 ± 7.42 kg to 114.5 ± 6.2 kg). The ratio of iEMG to 1RM increased (p<.05) for LoRep and decreased(p<.05) for HiRep from pretest to posttest. In summary, low RM loads increase activation and strength leading to an increased iEMG/1RM ratio. Conversely, high RM loads increase strength but not activation leading to a decreased iEMG/1RM ratio. In conclusion, the mechanism of strength increase by experienced weight lifters is dependent on the RM loads.