Acute effect of different exercise intensities and differences related to age on muscle performance in young and older women

BACKGROUND: The aim of this study was to compare the acute effect of different exercise intensities on the number of repetitions and total volume and differences related to age on the fatigue index. METHODS: Twelve young women (19.0 +/- 1.6 years) and ten older women (66.6 +/- 5.8 years) performed two experimental sessions for the elbow flexor muscles in a balanced cross-over design. In one experimental session, the participants performed three sets to concentric muscle failure at 100% of 10-12 maximum repetitions (RM). In the other experimental session, the participants performed two sets of 12 repetitions and one final set until concentric muscle failure at 90% of 10-12 RM. A 90-second rest interval was adopted between sets. RESULTS: The session performed at 90% of 10-12 RM showed a higher number of repetitions in the second and third sets and a greater total volume, compared to the session at 100% of 10-12 RM for both young and older women (all P< 0.05). However, significant no differences were observed in the fatigue index between the young and older women for the sessions performed at 90% or 100% of 10-12 RM (P>0.05). CONCLUSIONS: These findings suggest that a 10% load reduction promotes a greater number of repetitions and higher total volume in young and older adults. Moreover, the results indicate that young and older women present the same Fatigue Index for the elbow flexor muscles.