Mark Kramer

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.

Tracking knee joint movement during activities of daily living can have the potential to transform the rehabilitation and functional assessment of patients. The present study evaluated the validity of a low-cost, instrumented knee brace to determine whether it was appropriate for the monitoring and quantification of human knee function during five activity-of-daily-living (ADL) tasks including walking, inclined walking, stepping, sitting, and object manipulation. A sensor platform was designed to acquire sagittal plane knee data from 13 healthy participants across five different tasks and compared to gold-standard motion analysis. The brace showed good-to-excellent validity (RMSE: 4.97–8.65°), with differences in knee joint angles and angular velocities noted during various ADLs, specifically during early and late portions of a given movement. The results for instantaneous knee joint angles and angular velocities were very similar to those of the gold-standard system (mean bias: 0.59–9.52°·s⁻¹), which may be applicable to everyday movement tasks, but may preclude analyses at a clinical level. Although the low-cost sensor platform shows promise an effective monitoring tool, it is not ready yet for a clinical application.

The rehabilitation of patients following anterior cruciate ligament reconstruction (ACLR) requires objective assessments that can identify between-limb asy

Background: Proprioception encompasses position sense, posture and body movements, providing essential sensory information for learning and controlling movements, which is critical for children’s motor development, coordination and school readiness. Existing proprioceptive tests are primarily clinical, costly and difficult to apply in resource-limited settings, thus creating a need for feasible and reliable tasks to evaluate proprioception. Aim: This study aimed to establish inter-rater and test-retest reliability of existing proprioceptive tasks. Setting: This study was conducted in the Mangaung area of South Africa, involving participants from a Quintile 3 school. Methods: Twenty-four participants (50% males and 50% females) between the ages of 6 and 9 years completed six proprioceptive tasks on two occasions, 5 days apart. The performances were video recorded and rated by three reviewers. Test-retest and inter-rater reliability of each task item was calculated using the intraclass correlation coefficient for a single rater and for absolute agreement across multiple raters. Results: Three of the tests exhibited moderate test-retest reliability (shoulder-level-arm-raise both arms, finger-to-nose total and shoulder-level-arm-raise total), and one showed good reliability (Finger-to-nose eyes closed). Inter-rater reliability showed greater consistency; excellent reliability was shown for two task items (Rhomberg and force perception), and three showed moderate reliability (shoulder-level-arm-raise, both arms, and preferred arm, angels-in-the-snow and reciprocal imitations). Conclusion: The proprioceptive task items were deemed reliable to use in a field-based setting for children. Contribution: This study provides the first evidence of reliability for field-based proprioceptive tasks for South African children, identifying several tasks that can be confidently applied in school and community settings.

Heavy schoolbags are common among school-aged adolescents, yet biomechanical consequences across developmental stages and between sexes remain poorly defined, especially in low- and middle-income countries. This study investigated the effect of schoolbag carriage on gait in South African adolescents. A total of 186 injury-free adolescents (ages 12–18) completed barefoot walking trials over a pressure platform under unloaded and loaded conditions. Spatiotemporal and kinetic gait parameters were recorded and normalized to body height and weight. Analyses included (1) comparison of schoolbag mass by sex and grade (ie, school year); (2) evaluation of gait by loading condition, grade, and sex; and (3) prediction of loaded-condition gait parameters by relative schoolbag mass. Grades 8 to 11 carried higher absolute loads and grade 8 carried highest relative loads, with 58% exceeding 15% body mass, but no sex differences were found. Load carriage increased stance and double support time; reduced swing phase; and elevated vertical forces, pressures, and loading rates. Females exhibited higher forefoot and midfoot pressures and narrower step width. Relative schoolbag mass predicted greater forefoot/heel loads, lower midfoot loads, and narrower step width. Schoolbag carriage imposes substantial biomechanical demands, particularly in early adolescence and among females, emphasizing need for age- and sex-specific guidelines to mitigate long-term musculoskeletal risk.

Context : Clinicians assessing limb symmetry after ACL reconstruction (ACLR) use various tools including functional tests (eg, countermovement jump [CMJ]) and isolated strength tests (eg, isometric isokinetic dynamometry). However, it is unclear how these different assessment modalities and calculation methods compare, which may have significant implications for clinical decision making when interpreting asymmetry. Design : A repeated-measures, cross-sectional observational study. Methods : Fourteen participants post-ACLR (phase 3 rehabilitation) and 25 healthy controls were assessed. Participants completed unilateral isometric knee extension testing on an isokinetic dynamometer and bilateral CMJ testing on a dual force plate system. Asymmetry was calculated using 5 different equations. Results : A within-group analysis showed that participants post-ACLR had significantly different asymmetry magnitudes when comparing the CMJ and isometric tests (mean difference = 5.64%–12.45%, P < .006). Healthy controls showed no difference in asymmetry between the 2 tests ( P > .617). A between-group analysis showed that the ACLR group was significantly more asymmetric than controls on both the CMJ test (mean difference = 7.95%–22.12%, P < .001) and the isometric test (mean difference = 14.02%–36.24%, P < .001). However, both testing methods exhibited adequate sensitivity (0.79) and specificity (0.99) for differentiating those with ACLR from healthy controls. Conclusion : Asymmetry values are highly dependent on the assessment modality (functional jump vs isolated strength). While participants post-ACLR were more asymmetric than healthy controls on both tests, the magnitude of their asymmetry differed significantly between the 2 tests. This finding indicates that asymmetry values from functional and isolated tests are not interchangeable and underscores the need for test-specific interpretation in clinical practice.

Netball is a popular, high-intensity team sport played globally by more than 20 million players. Due to the high intensity and high participation levels, there is a high injury prevalence. The lower back region has been identified as the third most common site of injury within female team sports, with somatotype also influencing injury rates within netball. The objective of this research was to evaluate changes and explore relationships between somatotype and lower back strength (LBS) during a single netball season in university-level female netball players. A lack of evidence was found to support a relationship between changes in LBS and changes in a raw ectomorph (p=0.741), mesomorph (p=0.677) and endomorph (p=0.81) somatotype score during a single netball season in university-level female netball players. Statistically significant differences were noted for mesomorph somatotype score which increased LBS (12.35 kg) at the end of the season compared with the beginning of the season (p=0.004). A relationship between whole-body muscle strength and a dominant mesomorph somatotype score is important in netball because increased strength leads to adequate lumbo-pelvic hip-complex stability, thus reducing injuries and improving athletic performance.

Rehabilitation following successful ACL reconstruction (ACLR) requires restoring physical strength, neuromuscular function, and psychological readiness. However, the interplay between reactive agility, strength, and psychological confidence across rehabilitation phases remains unclear, particularly when compared to uninjured individuals. This study investigates the interrelationships between the reactive agility test (RAT), the isometric mid-thigh pull (IMTP), and the anterior cruciate ligament return-to-sport after injury (ACL-RSI) scale across three rehabilitation phases (Phase 4 [P4], return-to-play [RTP]1, and RTP2) following ACLR. The aim was to examine how reactive agility, strength, and psychological readiness evolve over time and compare ACLR participants to a healthy control group. Fifteen ACLR participants (15–27 years old) and thirty healthy controls (18– 30 years old) completed RAT, isometric mid-thigh pull (IMTP), and ACL-RSI assessments. ACLR participants were assessed at three rehabilitation phases (P4, RTP1, and RTP2), while controls completed a single testing session. Repeated measures analyses were used to track mean changes in performance across rehabilitation phases, and between-group comparisons were conducted using independent samples tests. ACL-RSI scores improved significantly across phases (p = 0.001), exceeding the smallest worthwhile change (SWC), indicating progressive psychological recovery. Reactive agility improved, with faster left-side decision-making (split 2) from P4 to RTP1 (p = 0.037), while right-side agility remained stable but met the SWC threshold (1.1%). Limited between-group differences in total RAT times and sub-phases suggest ACLR participants regained agility comparable to controls. IMTP strength plateaued after RTP1, reinforcing the greater role of agility and cognitive factors within the RTP framework. Reactive agility and psychological confidence progressively improved post-ACLR, with decision-making speed recovering earlier than acceleration ability. Minimal between-group differences suggest rehabilitation effectively restores agility, but directional asymmetries and plateaued strength warrant targeted interventions. Future research should explore neurocognitive training to optimize RTP outcomes and minimize re-injury risk. Clinical trial number not applicable.