Equivalence of self-selected versus imposed intensity in resistance training: effects on muscle mass, strength, and performance in postmenopausal women.

Abstract

Objective: The objective of this study was to investigate the equivalence between resistance training protocol with self-selected intensity (RT-SSI) and resistance training protocol with imposed intensity (RT-II) in postmenopausal women.

Methods: A randomized study involving 49 women was carried out. Participants were randomly assigned to either RT-II or RT-SSI. The RT-II group performed with a training load initially imposed at 60%, increasing to the 70%-85% range of one maximum repetition (1RM), while the RT-SSI group performed with a training load self-selected by the volunteers for 12 weeks. Muscle strength (1RM), the 6-minute walk test (6MWT), and body composition were assessed before and after the intervention.

Results: Both groups showed significant improvements in strength (P<0.001), muscle mass (P=0.027), and physical performance (P=0.023) after the 12-week intervention. However, there were no significant differences in the effects of the time/group interaction on muscle mass (P=0.750), strength (P=0.651), and physical performance (P=0.724). The equivalence analysis indicated Cohen d values for the effect estimate above the lower limit value for equivalence (d=-0.5). These results suggest that there is no evidence of the inferiority of RT-SSI in relation to RT-II for muscle mass, muscle strength, and physical performance. However, equivalence between interventions was not established, as the upper limits for equivalence were exceeded by the 90% CI.

Conclusion: Our findings indicated that RT-SSI is comparable to RT-II in terms of muscle mass, muscle strength, and physical performance gains in postmenopausal women.