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Abstract

International Journal of Exercise Science 16(4): 1228-1243, 2023. The study aimed to investigate sex differences and the effect of physical activity on the hamstring:quadriceps (H:Q) ratio, activities of daily living (ADLs), and the Functional Movement Screen (FMS) in older adults. Thirty older adults (72.56 + 6.22) completed maximal voluntary isometric contractions (MVICs), ADLs, the FMS, and three closed-kinetic chain exercises (CKCs); front lunge (FL), side lunge (SL), and bilateral squat (BLSQ). Electromyography was recorded from the biceps femoris (BF) and vastus lateralis (VL) on the dominant and non-dominant limbs during the MVICs and CKCs. Raw EMG recordings were normalized to MVICs and analyzed for root mean square (RMS). The H:Q ratio was calculated using RMS as BF/VL. It was determined that males had significantly higher H:Q ratios during the FL (p = 0.002), SL (p = 0.012) and BLSQ (p = 0.023), as well as higher RMS of the BF during the FL (p = 0.031), SL (p = 0.01), and BLSQ (p = 0.042). Females scored higher on the ADLs and FMS. A significant positive correlation was observed between ADLs and RMS of the VL (p < 0.05, r > 0.40), whereas a negative correlation was observed between ADLs and RMS of the BF (p < 0.05, r < -0.5). The results suggest that males may activate their hamstrings more effectively than females and that females may tend to remain quadriceps dominant. High motor unit recruitment of the hamstring muscles may coincide with reduced functional ability, whereas high motor unit recruitment of the quadriceps may coincide with enhanced functional ability.

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