Journal of Functional Morphology and Kinesiology最新文献

Background: Acute alterations in biomechanical and viscoelastic muscle properties provide important insight into early fatigue mechanisms; however, their dependence on specific muscle contraction types remains insufficiently understood. Therefore, the aim of this study was to quantitatively compare the acute effects of eccentric, concentric, isometric, and mixed contractions on the biomechanical and viscoelastic properties of the biceps brachii using myotonometry. Methods: Eighty healthy men aged 40 to 50 years were randomly assigned to four contraction conditions: eccentric, concentric, isometric or mixed concentric-eccentric. Each participant performed four sets of isolated biceps brachii exercise to volitional failure. Myotonometric measurements of tone, stiffness, decrement, relaxation and creep were collected before exercise and after each set. Changes within and between contraction types were analyzed. Results: Muscle responses differed significantly depending on contraction type. Dynamic contractions induced immediate viscoelastic changes, with significant reductions in relaxation time after eccentric (p = 0.027), concentric (p = 0.026), and mixed contractions (p < 0.001), while no changes were observed after isometric contraction (p = 0.285). Stiffness remained stable across all contraction types (p > 0.05). Mixed contractions showed a biphasic response in decrement with a significant effect across series (p = 0.049), identifying decrement as the most sensitive indicator of early fatigue, whereas isometric contraction produced no significant modifications in any parameter. Conclusions: Dynamic muscle work induces rapid and contraction-dependent shifts in viscoelastic properties, whereas stiffness appears resistant to short-term loading. Isometric contractions display minimal mechanical disturbance. Myotonometry proved effective in detecting early fatigue-related changes and decrement may serve as a key marker of short-term muscle adaptation.

Background: The Identification of Functional Ankle Instability (IdFAI) questionnaire is widely used to screen for functional ankle instability (FAI), but its link to objective landing kinetics in multidirectional sports like netball is not well-understood. This study aimed to (i) compare landing kinetics between idFAI stratified netball players, and (ii) examine associations between IdFAI scores with dynamic postural stability (DPS) indices and peak vertical ground reaction forces (PvGRF) during vertical drop landings. Methods: A cross-sectional exploratory study using a repeated-measures landing protocol was conducted on female university netball players (n = 24), stratified into FAI (n = 12) and non-FAI (n = 12) groups using the IdFAI (≥11 indicating possible FAI). Participants completed 18 unilateral drop jump landings in forward (FW), diagonal (DI), and lateral (LA) directions. Ground reaction forces (GRFs) were recorded to obtain DPS and PvGRF metrics (1000 Hz). Mann-Whitney U tests compared FAI groups, and Spearman correlations assessed associations (p < 0.05). Results: Players with FAI showed greater anteroposterior instability during LA landings (U = 33.5, p = 0.020, ES = 0.65). IdFAI scores correlated moderately with lateral anteroposterior deficits (rs = 0.473, p = 0.020, CI = 0.062-0.746). Conclusions: These findings suggest that players with greater FAI display increased anteroposterior instability during LA landings, with higher IdFAI scores moderately associated with these deficits. Despite the small exploratory, hypothesis-generating sample, the results emphasize the practical relevance of direction-targeted landing-stability training to improve DPS in vertical landings. This may provide insight into ankle-injury risk among FAI netball players, given that LA landings represent a documented ankle sprain mechanism.

Ten years have already passed since we made this journal available to the academic community, I must say that after all the results we have achieved in these ten years, I was not wrong to launch and found this journal and for this I thank the Founder and Chairman of the MDPI Board, for believing in me and granting me this important mission and trust [...].

Objectives: To assess intra-session reliability of isometric and isotonic shoulder external rotation (ER) strength tests and to compare their outcomes. Methods: Thirty-eight healthy subjects (19 females; 19 males; 25.7 ± 6.0 years; 175 ± 9 cm; 70.3 ± 11.4 kg) completed a shoulder ER strength assessment including Prone and Standing ER Isometric tests and Seated 5 repetition maximum (RM) ER tests. Normality was checked with the Shapiro-Wilk test. Reliability was assessed using the CV and ICC (3, k, 95% CI). Linear mixed models examined sex and dominance effects. Correlations and multiple regression tested associations between tests (p < 0.05). Results: All tests performed displayed "excellent" reliability scores (CV from 1.9 to 3.1% and ICC from 0.970 to 0.994). No significant effect of dominance was observed in any strength test. Males showed significantly higher values than females in both Prone (3.8% higher, p < 0.001) and Standing (2.7% higher, p = 0.003) isometric ER strength tests. Prone and Standing isometric tests were moderately correlated (r = 0.62, 95% CI [0.46, 0.74], p < 0.001). A regression model explained 52.4% of the variance in Seated 5 RM ER strength (R² = 0.524, p < 0.001), with Prone isometric strength emerging as a significant predictor (β = 0.612, p < 0.001). Conclusions: This study provides previously unreported 5 RM shoulder ER strength values in healthy adults, with all included tests showing excellent reliability. Isometric measures did not fully capture isotonic ER strength. Males outperformed females in isometric tests, but no gender difference was observed in Seated 5 RM strength.

Background: Despite the increasing interest in combat sports within higher education, studies on technical skill acquisition among novice female students remains limited. This study examined the effects of a short-term structured boxing program on the acquisition and retention of fundamental technical skills, focusing on stance (S), straight punches (SP), hooks (H), and uppercuts (U) among novice female university students. Methods: Technical performance was assessed under static and dynamic conditions at baseline (T1), after four weeks of course (T2), and at a two-month follow-up (T3) using customized scoring system. Handgrip strength (HG) and countermovement jump (CMJ) were measured as exploratory neuromuscular outcomes. Results: Results showed significant improvements in all technical skills at T2 compared with T1, in both static and dynamic executions (p < 0.001). Straight punches showed higher composite scores than hooks and uppercuts, while static performance was superior to dynamic execution (p < 0.001). Compared with T2, T3 showed a partial decline in performance for each skill in both executions (p < 0.001) (S_static = -18%; SP_static = -17%; H_static = -19%; U_static = -19%; S_dynamic = -22%; SP_dynamic = -18%; H_dynamic = -19%; U_dynamic = -21%), although T3 values generally remained above T1 baseline (S_static = +3%; SP_static = +19%; H_static = +22%; U_static = +29%; S_dynamic = -7%; SP_dynamic = +29%; H_dynamic = +29%; U_dynamic = +31%). HG showed a significant time effect (p = 0.005), while CMJ did not change significantly. Conclusions: These findings indicate that a short-term structured boxing program can effectively improve the technical boxing skills in female beginners. This supports the inclusion of a boxing course in university sport science curricula to enhance technical, motor, and educational development.

This paper presents the rationale and design of a study of growth and development in young track and field athletes: the EXcellence and PERformance in Track and field (EXPERT) study, and details the methodologies used. Background: Longitudinal research examining individual-environment interactions in youth athletic development is scarce for track and field. Objectives: The EXPERT study investigates how individual (anthropometry, maturation, motivation) and environmental (family, coach, club) characteristics influence developmental trajectories in youth track and field athletes. Methods: A mixed-longitudinal design will follow 400 athletes (200♂, 200♀; aged 10-14 years) from 40 Portuguese clubs across five cohorts assessed biannually over three years. Guided by Bronfenbrenner's bioecological model, assessments encompass individual, performance, health, and environmental domains. Data quality control will consist of rigorous training of all research team members, implementation of standardized protocols, a pilot study, and an in-field reliability study. Multilevel growth models will examine trajectories and predictor effects of predictors. Conclusions: EXPERT will provide evidence to optimize training and support holistic youth athlete development.

Background: The subacromial space, measured as the acromiohumeral distance (AHD), is a key determinant of shoulder biomechanics and injury risk. Athletes performing repetitive upper-limb resistance training are particularly exposed to cumulative tendon stress. Musculoskeletal ultrasound (US) enables dynamic, cost-effective assessment, yet its role in strength athletes remains underexplored. The aim of this study was to determine whether young adults engaged in regular upper-limb weight training present a narrower acromiohumeral distance and a higher prevalence of ultrasound-detected tendon abnormalities compared with non-weight-training individuals. Methods: We conducted a post hoc subanalysis of a cross-sectional cohort of 66 young adults (18-45 years; mean 29.6 ± 9.0 years; 27 men/39 women) evaluated with standardized shoulder US. Participants were classified as weight-training (n = 15; 36.2 ± 5.7 years; 11 men/4 women) or non-weight-training (n = 51; 27.6 ± 8.8 years; 16 men/35 women). AHD was measured in millimeters, and abnormalities of the supraspinatus, subscapularis, long head of the biceps tendon (LHBT), and subacromial-subdeltoid bursa were recorded. Between-group comparisons used Welch's t-test or χ²/Fisher's exact test; effect sizes were expressed as Cohen's d or odds ratios (OR). Multiple testing was corrected with the false discovery rate (FDR). Results: Weight-training participants exhibited a significantly smaller AHD (7.13 ± 0.54 vs. 7.49 ± 0.68 mm; t (28) = -2.12, p = 0.038; mean difference -0.36 mm, 95% CI -0.70 to -0.03; Cohen's d = -0.56). Supraspinatus tendinopathy was more prevalent in weight-training athletes (93.3% vs. 41.2%; OR 17.7, 95% CI 2.16-145.8; FDR-adjusted p = 0.003). Subscapularis tendinitis (40.0% vs. 17.6%; OR 3.58, 95% CI 1.00-12.88; FDR p = 0.14) and LHBT tenosynovitis (20.0% vs. 3.9%; OR 6.82, 95% CI 1.02-45.8; FDR p = 0.09) showed non-significant trends. Conclusions: Upper-limb weight training in young adults is associated with reduced AHD and a markedly higher prevalence of supraspinatus tendinopathy. Ultrasound proved valuable for early detection of structural and morphological alterations in shoulder soft tissues. Preventive strategies focusing on load management, exercise technique, and targeted strengthening should be prioritized.

Background: Impaired postural balance is a common feature in individuals with chronic obstructive pulmonary disease (COPD), increasing their risk of falls. This study aimed to evaluate the test-retest reliability of force platform parameters used to assess postural balance in individuals with COPD. Methods: A test-retest reliability study was conducted with participants diagnosed with moderate to severe COPD. Each participant completed two standardized balance assessments on a force platform, separated by a seven-day interval. Center of pressure (COP) parameters-including sway area, mean velocity, and path length-were analyzed under eyes-open and eyes-closed conditions. Reliability was determined using intraclass correlation coefficients (ICC), standard error of measurement (SEM), and coefficient of variation (CV). Correlations were performed between force platform parameters, the Timed Up and Go (TUG) test, and the Downton Fall Risk Scale. Results: Twenty individuals with COPD (mean age: 67.8 ± 6.1 years; forced expiratory value in the first second: 54 ± 12% predicted) were evaluated. The COP parameters demonstrated good to excellent test-retest reliability (ICC = 0.82-0.95) across all conditions, with low measurement error (SEM < 10%). Moderate correlations were found between force platform parameters and both TUG performance (r = 0.52-0.67) and Downton scores (r = 0.48-0.61). Conclusions: Force platform measurements show high reliability for assessing postural balance in individuals with COPD. These findings support the use of objective balance assessment tools in pulmonary rehabilitation and for monitoring fall risk in this population.

Background: Evidence suggests that physical activity and fitness tend to decline during the transition to higher education, yet the influence of institutional environment on these variables remains unclear. Objectives: This study aimed to compare physical fitness and physical activity levels between first-year students from two higher education institutions within the same national context. Methods: Fifty-eight male university students (IPB (Instituto Politécnico de Bragança): n = 31; IPG (Instituto Politécnico da Guarda): n = 27; mean age IPB = 19.2 ± 1.8 years; IPG = 19.8 ± 5.5 years) were assessed for body composition, handgrip strength, mid-thigh pull, standing long jump, stork balance, flexibility, and estimated VO_2max (StepTest4all). Physical activity levels were determined using the International Physical Activity Questionnaire (IPAQ) and were classified as low, moderate, or high. Between-group comparisons were performed using independent samples t-tests, with statistical significance set at p < 0.05. Results: Students from IPB presented significantly higher IPAQ scores (2.97 ± 0.18) compared with those from IPG (2.56 ± 0.64; t = 3.235, p = 0.003, d = 0.90), along with superior standing long jump performance (1.95 ± 0.15 m vs. 2.12 ± 0.24 m; t = -3.239, p = 0.002, d = 0.85). No significant differences were observed for body composition, strength, flexibility, balance, psychological well-being or VO_2max (all p > 0.05), although small effects were noted for flexibility (d = 0.50) and VO_2max (d = 0.48). The distribution of physical activity categories revealed that 96.8% of IPB students were classified as highly active, whereas IPG students were more evenly distributed across high (63.0%), moderate (28.6%), and low (7.4%) activity levels. Conclusions: These findings indicate that institutional environment and access to exercise opportunities may influence physical activity behavior and lower-limb power in university students. Promoting structured physical activity programs and recreational opportunities within higher education may help sustain adequate fitness and health in this population.

Background: Tibial pilon fractures are, in most cases, complex injuries caused by high-energy trauma. This type of fracture requires surgical stabilization and immobilization that impairs ankle function by reducing range of motion, muscle strength, and affecting the mechanical properties of the muscles. Methods: We evaluated 22 patients who required surgery for tibial pilon fractures and 22 age-matched healthy controls. Dynamometry assessed the isometric strength of the dorsiflexors and plantar flexors. Myotonometry of the tibialis anterior, peroneus longus, and medial and lateral gastrocnemius muscles analyzed the muscle tone, biomechanical (stiffness and decrement), and viscoelastic properties (mechanical stress relaxation and ratio of relaxation time to deformation time (creep). Results: Compared to the control group, the patients had significantly decreased isometric strength in both the dorsal flexors and plantar flexors on the affected side. Myotonometric measurements did not reveal significant differences in the tibialis anterior and peroneus longus muscles. Both medial and lateral gastrocnemius muscles exhibited significantly increased frequency and stiffness, and significantly decreased relaxation and creep in patients when compared to the control group. Conclusions: When compared to healthy controls, patients with surgically treated unilateral pilon fracture had a decreased isometric muscle force of ankle dorsiflexors and plantar flexors of both affected and non-affected lower limbs. Myotonometry indicated increased frequency and stiffness, along with decreased values of viscoelastic parameters (stress relaxation time and creep) in the medial and lateral gastrocnemius muscles on both sides.