Endocrine and metabolic consequences of off-season exercise cessation versus reduction in highly trained Division I female basketball players: a randomized controlled parallel-group study.

The off-season may induce adverse metabolic adaptations in highly trained Division I athletes due to reduced training load. Myonectin, a skeletal muscle-derived myokine, may be a sensitive marker of physical-activity change; however, its response to different off-season training strategies in highly trained female basketball players remains unclear. This study compared the effects of exercise cessation versus exercise reduction on circulating myonectin levels and metabolic health in highly trained Division I female basketball players. Thirty-four highly trained Division I female basketball players were allocated to either an exercise cessation (EC) group or an exercise reduction (ER) group during a 4-week off-season. Assessments were performed at baseline (3 days post-season; T0), after 2 weeks (T2), and after 4 weeks (T4). Outcomes included circulating myonectin, free fatty acids (FFA), high-sensitivity C-reactive protein (hs-CRP), and glucose-insulin homeostasis assessed using a standard 75 g oral glucose tolerance test. A significant group × time interaction was observed for circulating myonectin, with a greater decline in the EC group compared with the ER group (p < 0.05). Exercise cessation was associated with larger increases in FFA and insulin area under the curve, along with a greater reduction in whole-body insulin sensitivity assessed by the Matsuda index. Changes in fasting-based indices of insulin resistance were modest and diverged from dynamic OGTT-derived measures. Short-term off-season exercise cessation induces greater endocrine and metabolic disturbances than exercise reduction in highly trained Division I female basketball players. Maintaining a reduced level of physical activity during the off-season may attenuate early detraining-related alterations in myonectin and insulin sensitivity. Clinical Trial Registration: Iranian Registry of Clinical Trials (IRCT20180822040849N8), registered 5 January 2019.