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AGING MAY CONTRIBUTE TO LEARNING EFFECTS BUT DOES NOT INFLUENCE RELIABILITY OF ISOMETRIC MUSCLE PERFORMANCE

Abstract

Little research has identified if aging presents potential learning effects or influences test-retest reliability during maximum voluntary isometric contraction (MVIC) testing. PURPOSE: To identify potential learning challenges and measures of test-retest reliability for isometric testing in young (YW), middle-aged (MAW) and older women (OW) in muscles of the upper and lower body. METHODS: Ninety women YW [n=30]: 23.8±1.3years, 166.3±3.9cm, 64.7±5.2kg; MAW [n=30]: 52.3±1.4years, 167.8±7.2cm, 64.0±3.4kg; OW [n=30]: 76.5±5.7years, 164.8±1.8cm,68.1±2.9kg) completed three trials of MVIC testing for the elbow flexors (EF) and extensors (EE), knee flexors (KF) and extensors (KE), and plantar-(PF) and dorsiflexors (DF). Testing consisted of 1set of 6 repetitions at each joint. Alternating contractions were performed between opposing muscle groups (i.e. EF then EE) and each contraction was separated by 30 seconds rest periods. Three trials (T)were performed with 7-10 days between the previous session. Two-way (age x Trial) repeated measures analyses of variance was performed for each muscle group in addition to relative reliability between T2and T3, with significance set at p<0.05. RESULTS: MVIC force significantly decreased between YW, MAW, and OW for the KE (p<0.001), KF (p<0.04), and PF (p<0.001). The YW and MAW displayed no differences for EF, EE, and DF, while, the OW were significantly weaker than both the YW and MAW for those muscle groups(p≤0.002). Significant differences were observed between T1 and T2 for the EF (+13.1%, p=0.04), EE(+8.7%, p=0.03), KE(+15.3%, p<0.001), KF(+9.6%,p=0.04)and DF(+6.8%, p=0.02)in OW. Similar changes were noted for the KF (+5.3%, p=0.01), KE(+6.2%, p=0.02)in MAW, while no differences were observed in YW. High reliability was observed betweenT2 and T3 across all exercises for YW (ICC: 0.91-0.99), MA (ICC: 0.88-0.99) and OW (ICC: 0.84-0.98). CONCLUSIONS: Learning effects were evident in MAW and OW during MVIC testing for upper and lower body muscle groups. Further, T2 and T3displayed high reliability across all age groups. These data support the inclusion of more than two maximal testing days to account for potential learning effects, in turn providing a more accurate representation of MVIC performance in MAW and OW.

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