Muscle quality index and phase angle responses to matched-volume resistance training at different frequencies in older women

PURPOSE: To compare the effects of two resistance training (RT) frequencies (two vs. three sessions per week) on phase angle (PhA), a bioimpedance-derived marker, and muscle quality index (MQI) in older women under matched weekly training volume. METHODS: Forty-five older women (G2x: n = 22; G3x: n = 23; 63.2 ± 4.5 years) completed 12 weeks of supervised RT. Outcomes included fat mass, FFM, resting metabolic rate, total body water, PhA, and MQI, calculated as one-repetition maximum (1RM) divided by the corresponding segment-specific fat-free mass (FFM) measured by DXA for the chest press, leg extension, and preacher curl exercises. This study represents a secondary analysis of data from a previously published trial, focusing on neuromuscular efficiency and PhA. RESULTS: MQI increased significantly over time in both groups (p < 0.001), with no time × group interactions observed across exercises. No group-level changes were detected for PhA, and mean fluctuations remained below the minimal detectable change. Fat mass decreased modestly in the 3×/week group, whereas FFM increased slightly in both groups. CONCLUSION: When weekly training volume was equated, RT performed two or three times per week resulted in similar improvements in MQI, with no group-level changes observed for PhA in older women.