Effects of an 8-week mental preparation program combining progressive muscle relaxation and mental imagery on self-determined motivation and dynamic postural control in youth female handball players: an experimental study.

INTRODUCTION: Mental preparation strategies are widely used in youth sport to enhance both psychological and motor performance; however, the combined effects of progressive muscle relaxation and mental imagery on self-determined motivation and dynamic postural control remain insufficiently explored. This study investigated the effects of an 8-week mental preparation program combining Jacobson's progressive muscle relaxation and mental imagery in cadet female handball players. METHODS: A quasi-experimental pretest-post-test design with two parallel groups was employed. Thirty-six cadet female handball players were allocated to an experimental group (n = 18) and a control group (n = 18). Self-determined motivation was assessed using the Sport Motivation Scale (SMS-28), and dynamic postural control was evaluated using the Lower Quarter Y-Balance Test (YBT-LQ) before and after the intervention. The experimental group completed three weekly mental preparation sessions in addition to their regular handball training, whereas the control group continued their usual training program. RESULTS: Significant improvements in YBT-LQ performance were observed over time in both groups, with greater gains in the experimental group (Time × Group interaction: p < 0.001, η p 2 = 0.37, 95% CI [0.13, 0.57]). Significant Time × Group interactions were also found for intrinsic motivation toward accomplishment (p < 0.001, η p 2 = 0.41, 95% CI [0.16, 0.60]), intrinsic motivation to experience stimulation (p < 0.001, η p 2 = 0.35, 95% CI [0.11, 0.55]), intrinsic motivation to know (p < 0.043, η p 2 = 0.12, 95% CI [0.00, 0.33]), identified regulation (p < 0.001, η p 2 = 0.31, 95% CI [0.08, 0.51]), and external regulation (p < 0.001, η p 2 = 0.55, 95% CI [0.31, 0.70]). The interaction for introjected regulation was small ( η p 2 = 0.02) and did not remain significant after correction. Amotivation decreased over time in both groups without a significant Time ×Group interaction (p = 0.097, η p 2 = 0.079, 95% CI [0.00, 0.25]). DISCUSSION: An 8-week mental preparation program combining progressive muscle relaxation and mental imagery improved dynamic postural control and promoted more autonomous motivational regulation in cadet female handball players. These findings support the integration of structured mental preparation strategies into youth handball training programs to enhance both psychological and motor performance.