Effects of 12 weeks resistance training on muscle quality and physical performance in normal-weight and obese older women.

Ageing and obesity are major public health issues, both associated with reductions in muscle mass, strength, and physical performance. Muscle quality, which integrates the morphological and functional characteristics of skeletal muscle, is a key predictor of independence and mortality in older adults. Obesity is linked to additional structural and functional alterations in muscle during ageing, alongside a potential anabolic resistance. Although resistance training (RT) has been shown to improve muscle mass and quality in older adults, evidence in older women with obesity remains limited. This study aimed to compare the effects of a 12-week progressive, whole-body RT programme on muscle quality parameters and physical performance in women aged 60-79 years with obesity (68 ± 4.21 years; body mass index [BMI] = 33.01 ± 2.62 kg/m²; body fat percentage= 42.23% ± 2.98%; n = 16) versus age-matched normal-weight women (66 ± 4.31 years; BMI = 22.60 ± 1.36 kg/m²; body fat percentage= 33.11% ± 3.61%; n = 14). RT was performed three times per week for 12 weeks. Before and after the intervention, morphological indicators of muscle quality (quadriceps muscle thickness and echointensity) and physical performance were assessed. Both groups showed significant post-training improvements in quadriceps thickness (time effect, p < 0.001); maximal strength in leg extension, leg flexion, leg press, chest press, and elbow extension (p < 0.001), lower-limb power, and muscle quality index (p < 0.001), as well as physical performance (p < 0.001); In conclusion, although the increase in muscle thickness and the reduction in body fat percentage were only significant in the normal-weight group, 12 weeks of RT are effective in improving functional parameters of muscle quality and physical performance in normal-weight and obese older women. This supports RT as an effective strategy to optimise musculoskeletal health in this population.