Effects of Rest Period/Number of Reps in Arm Specific Resistance Exercise on Acute Hormonal Responses

Abstract

PURPOSE: In the present study, we investigated how resistance exercises with different rest times affect local hormone production. To determine the local hormonal responses induced by resistance exercise (RE), we designed RE protocols targeting the biceps and triceps muscles only. We hypothesize that short rest periods with light-medium weight/high reps induce higher hormonal responses than long rest periods with heavy weight/ lower reps. METHODS: 7 male students (24–37 yrs) were divided into 2 groups. All participants performed 3 exercises for biceps and triceps, respectively. For each exercise the participants executed 3 sets, each set taken to failure, the rest period between sets and exercises was 30 sec in the first groups (Short rest group, S). The weight was a weight the participants could perform between 15–25 reps (50% 1RM). The second group (Long rest group, L) performed the same training protocol except for the rest period between sets and exercises which has been lengthened to 3 min and the weight which has been increased to a max of 6–8 reps (80% 1RM). Blood collection was conducted immediately before, immediately after, 15 min, 30 min and 60 min after the exercise session. Blood samples were then analyzed for testosterone, free testosterone, IGF-1 and GH. The experiment was conducted twice with a recovery period of 2 months in a cross-over fashion in order to obtain n=8 for each group, each participant executing both RE protocols. RESULTS: The S group showed a significantly greater hormonal increase immediately after RE only in GH (282%, p<0.05 vs. rest, p<0.05 vs. before) . RE induced no significant changes in other anabolic hormones (testosterone, free testosterone and IGF-1). CONCLUSION: Arm only exercises can induce important acute hormonal increases if conducted with high intensity (short rest, high reps).