(16) STRENGTH GAINS OCCUR INDEPENDENT OF SIZE AND QUALITY CHANGES AFTER SIX WEEKS OF MODERATE AND HIGH-VOLUME TRAINING IN OLDER ADULTS: PRELIMINARY RESULTS

Purpose: Longitudinal aging studies indicate that the gradual decline in muscle strength is more closely linked to changes in muscle quality than to muscle mass. Muscle quality, often assessed using skeletal muscle echo intensity (EI) via B-mode ultrasonography, reflects intramuscular adiposity and fibrous tissue content. While high-intensity resistance training is commonly prescribed to mitigate these effects, it remains unclear whether adjusting training volume enhances muscle quality and strength—especially after short-term resistance training—and whether these improvements are related. The purpose of this study was to investigate whether moderate-volume (2 sets per exercise) or high-volume (6 sets per exercise) supervised lower-body resistance training enhances quadriceps strength, size, and quality. Additionally, we examined whether these improvements were associated. Methods: Fourteen older adults (7 males, 7 females; mean ± SD age = 71 ± 7 years, BMI = 24.6 ± 3 kg/m²) performed a supervised, lower-body resistance training program twice per week for 6 weeks. Participants were randomly assigned to perform either 2 sets (n=7) or 6 sets (n=7) of the leg extension, trap bar deadlift, and leg press (i.e., 6 or 18 sets total/session), with a full range of motion at 85% of their estimated one-repetition maximum (1RM) until failure. 1RM leg extension strength and vastus lateralis (VL) cross-sectional area (CSA) and EI were measured before and after the intervention. Results: In the moderate-volume group, leg extension 1RM strength increased by 49.1% (p < 0.01, d=2.25) VL CSA by 8.3% (p=0.400, d=0.342) and VL EI decreased by 0.8% (p=0.524, d = 0.256). In the high-volume group, leg extension 1RM strength increased by 37.3% (p=0.011, d=1.38), VL CSA by 0.1% (p=0.685, d=0.16), and VL EI increased by 1.3% (p=0.732, d=0.136). For the moderate-volume group, pre-post change scores showed no significant correlations between changes in 1RM leg extension strength and VL EI (r=0.255, p=0.581), changes in 1RM leg extension strength and VL CSA (r=-0.267, p=0.563), or changes in VL CSA and VL EI (r=-0.281, p=0.542). Similarly, in the high-volume group, pre-post change scores revealed no significant correlations between changes in 1RM leg extension strength and VL EI (r=-0.178, p=0.702), changes in 1RM leg extension strength and VL CSA (r=-0.042, p=0.928), or changes in VL CSA and VL EI (r=-0.382, p=0.398). Conclusions: After six weeks of moderate or high-volume resistance training, we observed substantial improvements in quadriceps muscle strength; however, these gains were not correlated with changes in muscle size or quality. Although preliminary, these findings suggest that EI may not be easily modified by resistance training or that its variability is influenced by multiple unrelated factors. Practical Applications: Enhancing muscle quality in older adults is a key goal for researchers and clinicians. While resistance training improves muscle strength, variations in training volume do not appear to significantly impact muscle size or quality. To effectively modify EI, longer-duration or multi-modal approaches may be necessary. Acknowledgements: None