1. Investigación

To assess the effects of a progressive resistance training program at different intensities on health-related quality of life, anxiety, and motivation towards engaging in physical activity among older people. Prospective, municipal multicenters, non-randomized controlled trial. 76 older adults were assigned to: vigorous intensity (n = 19), vigorousmoderate intensity (n = 21), moderate intensity (n = 19), or control group (n = 17). The exercise groups performed six exercises with elastic bands per session, twice a week, for 8 months. Vigorous intensity, vigorous-moderate intensity and moderate intensity group performed 6, 10 and 15 repetitions, respectively. Health-related quality of life was assessed using the 36-Item Short Form Health Survey, trait and state anxiety using the State-Trait Anxiety Inventory, and motivation towards engaging in physical activity using the Behavioural Regulation in Exercise Questionnaire. The moderate intensity group showed a significant increase in the summary of the physical components of health-related quality of life (p = 0.001; ηp2 = 0.158) and a significant decrease in external regulation (p = 0.002; ηp2 = 0.145) and amotivation (p = 0.013; ηp2 = 0.97). In contrast, the vigorous intensity group showed a significant increase in state anxiety (p = 0.004; ηp2 = 0.076) and a significant decrease in introjected regulation (p = 0.018; ηp2 = 0.097). Moderate intensity strength training programs are best suited for older adults because they improve health-related quality of life and decrease less self-determined forms of regulation, all without increasing anxiety states.