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 exercise cessation versus reduction on circulating myonectin 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 four-week off-season. Assessments were performed at baseline (three days post-season; T0), after two weeks (T2), and after four 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.