Objective: This study aimed to investigate the acute patellar tendon (PT) responses to different isometric resistance training regimens in healthy individuals, with a particular focus on low-intensity blood flow restriction training. Design: Randomized controlled experimental study. Methods: Sixty-six participants (22.3 ± 3 years) were randomly assigned to one of three groups: high-intensity isometric exercise (HI; 70% maximal voluntary isometric contraction [MVIC]), low-intensity isometric exercise with sham blood flow restriction (LI-Sham; 30% MVIC + 20 mmHg), or low-intensity isometric exercise with blood flow restriction (LI-BFR; 30% MVIC + 80% arterial occlusion pressure [AOP]). All participants performed five sets of 30-s isometric knee extensions. Patellar tendon thickness was assessed using ultrasonography at three sites (25%, 50%, and 75% of tendon length) before and immediately after exercise. Vastus medialis thickness and MVIC were also assessed. Results: Patellar tendon thickness decreased significantly over time, with a significant Group × Time interaction (F(2, 315) = 27.94, p < 0.001). When averaged across measurement sites, the estimated reductions were −0.586 mm in HI, −0.545 mm in LI-BFR, and −0.242 mm in LI-Sham. Reductions were greater in HI and LI-BFR than in LI-Sham (both Holm-adjusted p < 0.001), whereas no statistically significant difference was detected between HI and LI-BFR (Holm-adjusted p = 0.416). Vastus medialis thickness showed significant Time and Group × Time effects (both p < 0.001), with greater increases in HI and LI-BFR than in LI-Sham. No significant Time or Group × Time effects were observed for MVIC (p = 0.100 and p = 0.409, respectively). Conclusions: A single session of LI-BFR induced an acute reduction in ultrasound-measured PT thickness that was greater than that observed with LI-Sham. No statistically significant difference in tendon-thickness change was detected between LI-BFR and HI; however, this finding should not be interpreted as evidence of equivalence. These findings are limited to immediate responses in healthy young adults and should not be interpreted as evidence of long-term tendon adaptation or clinical benefit.
Motor competence is a key determinant of children’s physical activity and sport participation; however, contemporary data describing motor competence proficiency in young children in England are lacking. This study aimed to describe motor competence proficiency in English children aged 4–7 years, examining differences associated with sex while accounting for age and deprivation. Five hundred and thirty-five children (264 boys, 271 girls; 5.4 ± 0.9 years) completed the Motor Competence Assessment (MCA) as a measure of motor competence. Performance was classified using age and sex specific normative values, and analysis of covariance was used to examine the effects of sex, age, and deprivation. Children generally demonstrated age-appropriate locomotor and stability competence, with only 4.5% classified as below average for standing long jump, 25.8% for shuttle run, 10.1% for jumping sideways, and 19.1% for shifting platforms. In contrast, object control proficiency was markedly lower, with 77% of children below average for ball throwing velocity and 59% below average for ball kicking velocity. As the only norm values available for the MCA are based on Portuguese children, extreme normative deviations documented here may reflect cross-cultural normative misalignment rather than genuine motor impairment in this sample. No sex differences were evident for locomotor or stability skills, and deprivation was not associated with performance in any motor competence domain. However, a significant sex-by-age interaction was observed for object control skills, with boys increasingly outperforming girls from age four to seven years. These findings suggest that motor competence in these children is not uniformly poor, but substantially poorer performance was observed in object control skills, particularly among girls, highlighting a need for targeted early childhood interventions.
Background: Core stability is the foundational link in the kinetic chain of tennis strokes, yet the specific impact of supplementary core conditioning on the neuromuscular development of adolescent female players remains poorly quantified. This study investigated the effects of an 8-week core training program on dynamic balance and static trunk rotation strength in 13–14-year-old female tennis players. Methods: In this parallel-group randomized controlled trial, 24 female tennis players were assigned to an experimental group (EG; n = 12) or a control group (CG; n = 12). The EG performed a 45–60 min supplementary core protocol (3 days/week) focusing on progressive overload, while the CG engaged in matched-duration low-intensity technical drills. Assessment tools included the Star Excursion Balance Test (SEBT) for dynamic balance and a digital rope dynamometer for static trunk rotation strength (forehand/backhand). Results: Mixed-model repeated-measures ANOVA revealed significant Group × Time interaction effects with large magnitudes. The EG demonstrated significant improvements in right-foot dynamic balance (0.83% increase; p = 0.005), forehand trunk rotation strength (13.41% increase; p = 0.001), and backhand trunk rotation strength (12.00% increase; p = 0.012); the control condition did not result in significant improvements in any variable over the 8-week intervention period (all p > 0.05). Conclusions: An 8-week structured core training program significantly improved right-foot dynamic balance and static trunk rotation strength in adolescent female tennis players relative to technical training alone. These findings support considering core-specific conditioning as a component of training for this population; however, as tennis-specific performance, injury risk, and kinetic-chain function during actual strokes were not directly assessed, claims regarding broader clinical or sport-specific performance benefits require confirmation in future research. Trial Registration: This trial was retrospectively registered in the Iranian Registry of Clinical Trials (IRCT; a WHO ICTRP Primary Registry) on 30 September 2026 (registration number: IRCT20260904070908N1). Prospective registration was not undertaken because it was not required by the approving institutional ethics committee at the time the study was conducted (2019); ethics approval is not regarded as a substitute for prospective registration, and this is acknowledged as a limitation.
This cross-sectional study examined the correspondence between objective and self-rated sports nutrition knowledge and its associations with information practices and supplement use. Seven hundred adult gym users residing in Croatia completed an online survey including a study-specific 14-item knowledge index. The median score was 11 of 14 (interquartile range, 9–12). Internal consistency was moderate (KR-20 = 0.703), but scalability was limited (Loevinger’s H = 0.231). Self-rated knowledge was weakly correlated with the score (Spearman’s ρ = 0.129; p < 0.001), and adjusted scores were similar between respondents reporting good and partial knowledge. Selecting scientific articles or PubMed as a main information source was associated with a 0.83-point higher score (95% confidence interval, 0.32–1.35). Among 628 current or previous supplement users, sometimes and always reading labels were associated with 1.86- and 2.05-point higher scores than never reading labels. These associations persisted in bounded-outcome and alternative-adjustment analyses. The overall association with four-level supplement-use status in the full sample was inconclusive (p = 0.095), although regular users scored higher than never-users in an individual nominal comparison. Information practices were associated with performance on the sampled questions, whereas self-ratings provided limited information about tested performance. The study-specific index and cross-sectional design limit conclusions about individual competence and causal relationships.
Background/Objectives: Sex- and category-specific body-composition references are scarce for Latin American and female football players. We used dual-energy X-ray absorptiometry (DXA), which quantifies lean soft tissue, fat, and bone mineral content (BMC) regionally in one low-dose scan, to describe body composition across Mexican national squads and to explore associations with playing position. Methods: We analyzed 272 DXA records acquired in 2026 under one standardized protocol (females: n = 133, under-15 [U15] to senior; males: n = 139, under-14 [U14] to senior) using 95% confidence intervals and height-adjusted, sex-stratified linear models with heteroscedasticity-consistent (HC3) standard errors and Holm correction. Results: Senior squads had 8.83 kg (females) and 13.23 kg (males) more total lean mass than the youngest category (Hedges’ g > 2) and 6.32 and 2.59 percentage points less body fat. Male fat mass was similar across categories (10.4–11.7 kg), suggesting that the lower body-fat percentage of older male squads reflected greater lean mass; in females, it reflected both greater lean mass and lower fat mass. Category remained associated with lean mass and BMC after height adjustment (Holm-adjusted p < 0.001) but was not significantly associated with male body-fat percentage (p = 0.118). No association between position and body composition was observed in females; male forwards had more lean mass and less fat than goalkeepers. Conclusions: These preliminary cross-sectional references allow staff to benchmark players against their own squad and to flag atypical lean or bone values for multidisciplinary review; they are not developmental trajectories or body-composition targets.
