The main objective of our study was to determine whether constant and variable practice conditions lead to the development of different memory representations (GMP) and as a result, they benefit performance of a skill differently. We compared one of the Generalized Motor Program (GMP) invariant features, i.e., relative timing, of the same variation of skill developed in constant and variable practice conditions. In two experiments, participants, naïve to the basketball, were practicing free throws, receiving the same amount of practice. In constant conditions they practiced at one distance only (4.57 m), whereas in variable conditions they practiced at seven (2.74, 3.35, 3.96, 4.57, 5.18, 5.79, and 6.4 m) and five (3.35, 3.96, 4.57, 5.18, and 5.79 m) distances, in Experiments 1 and 2, respectively. We found that relative timing of skills developed in constant and variable practice conditions is the same, confirming that these practice conditions form the same memory representation. However, we also observed that constant practice (CP) conditions resulted in overall shorter movement time as compared to the skill practiced in variable conditions. We hypothesized that it may be due to the facilitation of parameters assignment as it takes place in especial skill.

Background: Sleep hygiene protocols (SHPs) have been shown to improve sleep and stress regulation; however, the role of cortisol in shaping downstream physiological and performance adaptations remains unclear. This study primarily examined the effects of a short-term SHP on sleep duration and salivary cortisol responses across resting, pre-exercise, and post-exercise states in female collegiate soccer players and, secondarily, whether cortisol statistically mediated selected aerobic and anaerobic performance outcomes. Methods: Fourteen players (22.1 ± 3.3 y; 157.8 ± 6.0 cm; 53.5 ± 3.9 kg) completed a randomised, counterbalanced crossover study comparing habitual sleep (no sleep hygiene protocol; nSHP) with a comprehensive SHP incorporating environmental, behavioural, and educational strategies. Salivary cortisol was sampled one hour post-waking and 30 min pre- and 15 min post-exercise during standardised testing sessions. Performance outcomes included vertical jump, sprint performance (40 m and repeated sprints [RAST]), and the Yo-Yo Intermittent Recovery Test Level 1. Linear mixed-effects models assessed cortisol responses, and mediation analyses explored cortisol–performance relationships. Results: After SHP, perceived (7.87 h vs. 6.5 h; p = 0.002, ESg = 1.0) and calculated sleep duration (8.5 h vs. 6.9 h; p = 0.004, ESg = 0.95) increased significantly. Cortisol was markedly lower following SHP at selected timepoints, including before RAST (−43.05%, p = 0.006, ESg = 0.84), with additional timepoint-specific, condition-dependent differences post-anaerobic and post-aerobic exercise (Δ = 7.37 and 5.98 nmol·L⁻¹, respectively; p < 0.001). Vertical jump height demonstrated significant total (9.92 cm, p = 0.002) and direct effects (7.72 cm, p = 0.034), and peak repeated-sprint performance showed a significant direct effect (p = 0.026). Cortisol did not significantly mediate any performance outcomes (ACME p > 0.05). Conclusions: Short-term sleep hygiene is associated with increased sleep duration, timepoint-specific modulation of cortisol responses, and selected anaerobic performance benefits; however, these effects were not explained by measured cortisol responses and are unlikely to be sustained without ongoing reinforcement or support, particularly in athletic populations.