Frontiers in Sports and Active Living

PurposeThe para-cycling classification system aims to minimize the impact of impairments on competition outcomes with the help of scientific evidence. This study investigated the impact of unilateral and bilateral ankle immobility on cycling performance, quantified by the maximal average mechanical power output (AMPO) over one revolution relative to that without ankle immobility. MethodsTen well-trained non-disabled cyclists performed all-out 6-second sprints on a cycle ergometer at 120 rpm under three conditions: without ankle foot orthoses (AFOs), with 1 AFO and with 2 AFOs immobilizing the ankle joint(s). Mechanical power output, pedal forces, cycling kinematics and surface-electromyography were measured. Maximal AMPO; ankle, knee and hip joint AMPO; and the amount of muscle excitation were calculated. ResultsWith 1 AFO and 2 AFOs, respectively, maximal AMPO was 96% (p<0.05) and 91% (p<0.001) of that without AFOs (1188 W). The decrease in maximal AMPO with ankle immobilization was less than the decrease in ankle joint AMPO (126 W decrease with 2 AFOs; p<0.001), due to an increase in hip joint AMPO (69 W increase with 2 AFOs; p<0.05). The amount of muscle excitation was not significantly different across conditions. ConclusionsThese findings provide a first quantitative and mechanistic indication of the impact of ankle immobility on cycling performance, which may offer valuable evidence to support the development of an evidence-based para-cycling classification system.

Objectives: Given the high injury burden in football and the documented limitations of strength-based screening, novel approaches are warranted. Adaptive Force (AF)being closer to injury-prone movements than pushing/pulling strength--offers an alternative. This study examined the association between AF-based muscle stability and musculoskeletal complaints in football players and compared AF-derived and conventional strength parameters in their discriminative capacity, complemented by a preliminary prospective follow-up. Methods: AF and maximal voluntary isometric contraction (MVIC) were measured in 23 male football players across five bilateral muscle groups (knee extensors/flexors; hip flexors/adductors/abductors). AF parameters (maximal isometric AF, maximal AF, AF-Ratio), MVIC and hamstrings-to-quadriceps (H:Q) ratio were compared between players with and without complaints assessed via questionnaire at baseline and six-month follow-up (n=13). Results: Stability deficits were strongly associated with complaints (OR=54.0, 82% side concordance). AF-Ratio discriminated clearly between players with and without complaints (d=-1.47), with hip abductors showing the strongest effect (d=-1.64). Players with subsequent complaints showed lower baseline AF-Ratio (d=-1.45) and more stability deficits (d=1.67). MVIC and H:Q ratio did not discriminate (p>0.430). Conclusion: The findings suggest that muscle stability assessment outperforms conventional strength parameters in discriminating players with and without complaints, with preliminary follow-up data providing tentative support for predictive value. The concept of functional instability syndrome (FIS) provides a mechanistic framework for non-contact injuries and musculoskeletal complaints. AF assessment offers potential for screening, including return-to-sport decisions. Further studies are needed to verify the results, investigate predictive value, and evaluate whether personalised stability-based interventions can reduce injury incidence.

BackgroundThe clinical assessment of knee stability after an Anterior Cruciate Ligament (ACL) injury is routinely conducted via operator-dependent physical examination tests (i.e. pivot shift) and standardized patient-reported outcomes. Unfortunately, both are unable to perceive and quantify the subtle rotational biomechanical deficiencies from an ACL tear. Although specialized laboratory-based motion capture systems may provide objective measurements, they are found in research institutions and thus, are not suitable for clinical use. In contrast, GATOR PRO is a clinic-based multimodal wearable sensor system that uses a machine learning (ML) model (ensemble deep learning) to differentiate and classify its data outputs for assessing in-vivo dynamic rotational knee stability. ObjectiveThe purpose of this study is to validate the deep machine learning model and its performance used in GATOR PRO, which integrates knee-mounted Inertial Measurement Units (IMUs) with ultrasound images to derive high-fidelity in-vivo biomechanical rotational data. Based on this data collected by the GATOR PRO, it is hypothesized that the model can effectively classify knee stability after ACL injury and reconstruction. MethodsThis prospective clinical study at Singapore General Hospital (SGH) (CIRB 2019/2766, PDPA-compliant) aimed to enroll 60 patients (30 ACL-deficient, 30 ACL-reconstructed [&ge;]6 months post-surgery). At the halfway point of the clinical trial, 29 patients (8 ACL-deficient, 21 ACL-reconstructed [&ge;]6 months post-surgery) were recruited through physician referral at SGH outpatient clinics to perform standardized chair-stand tests. An ensemble deep learning model that combines convolutional (EfficientNet) and time-series (InceptionTime) classifiers is used to output binary stability classifications (ACL-deficient/ACL-reconstructed). The models performance was evaluated using 10-fold stratified cross-validation with patient-wise splitting, repeated across 100 random seeds to assess variability. ResultsAt the halfway point of the trial, the ensemble model performance with regard to the Receiver Operating Characteristic area under the curve (ROC-AUC) was 0.8365 (SD: 0.042, p-value < 0.001), and the classification accuracy was 75.9% (SD: 3.2%) when the model was tested on the 29 CIRB-approved patients. For the ACL-reconstructed class, the performance indicators were as follows: precision 71.4%, recall 93.8%, F1-score 81.1%. For the ACL-deficient class, the indicators were: precision 87.5%, recall 53.8%, F1-score 66.7%.Against the clinical pivot shift tests low sensitivity (24-32%), the model delivers an almost 2X better sensitivity (53.8%)[2, 3], with a comparable specificity (93.8% vs. 90-98%) ConclusionThe multimodal machine learning model was able to perform at a level that was relevant to clinical classification (AUC-ROC 0.8365, accuracy 75.9%) in differentiating between ACL-deficient and ACL-reconstructed knees. Moreover, the model demonstrated far superior sensitivity than previously published estimates for manual pivot shift testing (53.8% vs. 24-32%). These findings demonstrate that rotational knee instability can be reliably differentiated in clinical settings with a ML model deployed on GATOR PRO data.

This cross-sectional derivation and internal validation study aimed to develop and internally validate a clinical triage scoring system (CTSS) for field-based identification of collegiate athletes requiring priority intervention for lumbopelvic-hip (LPH) dysfunction. A total of 864 collegiate athletes (mean age 21.3 {+/-} 2.4 years; 80.8% male) were recruited from 10 universities. Participants underwent standardized assessments including demographic characteristics, clinical history, and LPH functional testing. Using an expert-adjudicated binary reference standard (priority intervention vs self-management), a multivariable logistic regression model was developed to derive the weighted CTSS. Model performance was evaluated using discrimination, calibration, and decision curve analysis (DCA), and internal validation was performed using 1,000 bootstrap resamples. Of the 864 participants, 463 athletes (53.6%) were classified as requiring priority intervention. The final 14-factor CTSS comprised 12 positive-weight predictors, such as localized LPH pain, muscle weakness, and higher body mass index, and 2 negative-weight predictors, positive Lasegues sign and hamstring weakness, which functioned served as safety-related modifiers. The model demonstrated acceptable discrimination (AUROC = 0.851, 95% CI: 0.824-0.876), with minimal optimism (optimism-corrected AUROC = 0.842) and excellent calibration (calibration slope = 1.000; calibration intercept = 0.000). A total score of [&ge;]9 was identified as the optimal threshold, yielding a sensitivity of 84.4% and specificity of 71.8%. DCA showed greater net benefit than treat-all and treat-none strategies across clinically relevant threshold probabilities (20%-50%), with a net benefit of 0.319 at a 50% threshold probability. The CTSS may provide a pragmatic field-based triage tool to support early identification of athletes who may require priority intervention, although external validation is needed before broader implementation in sports medicine settings.

ABSTRACT Background: Athletes who return to soccer after anterior cruciate ligament reconstruction (ACLR) remain at elevated risk of secondary injury despite meeting conventional discharge criteria, and neuromuscular deficits in the reconstructed limb are known to be exposed by fatigue. Objective: To determine whether match-play fatigue differentially affects muscle stiffness, countermovement jump (CMJ) force symmetry, and rate of force development (RFD) asymmetry between soccer players with a history of ACLR and uninjured teammates. Methods: A prospective, cross-sectional, matched-control study enrolled 128 competitive soccer players (64 ACLR, 6-22 months post-surgery; 64 uninjured controls) across five recruitment waves (February-June 2026). Bilateral CMJ peak vertical force, jump height, RFD, and myotonometric stiffness of the rectus femoris (RF), vastus medialis (VM), and biceps femoris (BF) were recorded immediately before and after a standardized competitive match. Fatigue was quantified from second-half heart rate (percentage of age-predicted maximum) and end-match rating of perceived exertion (RPE). Within-group pre-to-post changes were evaluated with paired t-tests, between-group differences in the magnitude of change with independent-samples t-tests, and associations between fatigue indices and asymmetry changes with Pearson correlations. Results: Match play reduced CMJ limb symmetry index (LSI) in both groups, but the decline was more than three-fold greater in the ACLR group, 92.6% (SD 5.4%) to 85.1% (SD 7.1%), than in control group, 97.3% (SD 3.9%) to 95.0% (SD 4.2%), group-by-time difference, p < 0.001, (d = 0.64). RFD asymmetry approximately doubled in the ACLR group, 10.6% (SD 4.1%) to 17.6% (SD 6.5%), compared with a smaller rise in control group, 4.6% (SD 2.4%) to 6.3% (SD 3.7%); p < 0.001, d = 0.77). Involved-limb stiffness losses in the ACLR group exceeded those of controls for the RF (-21.2 vs. -9.2 N/m, p < 0.001), VM (-17.7 vs. -6.1 N/m, p < 0.001), and BF (-13.3 vs. -6.6 N/m, p < 0.001), whereas uninvolved-limb stiffness losses did not differ between groups (all p > 0.05). Fatigue markers (heart rate, RPE) were not significantly correlated with the magnitude of individual asymmetry change (|r| [&le;] 0.18, p > 0.15). Conclusions: In competitive soccer players 6-22 months after ACLR, match-play fatigue selectively compromises stiffness and explosive force output of the reconstructed limb, widening inter-limb asymmetries beyond what is seen in uninjured teammates, even though global cardiovascular and perceptual fatigue were comparable between groups. These findings suggest that return-to-sport testing performed only in a rested state may underestimate residual neuromuscular deficits, and support fatigue-inclusive assessment protocols before athletes are cleared for unrestricted competition. Abbreviations: ACL: anterior cruciate ligament, ACLR: anterior cruciate ligament reconstruction, BF: biceps femoris, CMJ: countermovement jump, HRmax: maximum heart rate, LSI: limb symmetry index, RF: rectus femoris, RFD: rate of force development, RPE: rating of perceived exertion, RTS: return to sport, VM: vastus medialis, SD: standard deviation. Keywords: Anterior cruciate ligament reconstruction, muscle fatigue, muscle stiffness, countermovement jump, limb symmetry index, rate of force development, soccer, return to sport.

Background: Quadriceps strength and landing mechanics are two modifiable factors associated with anterior cruciate ligament (ACL) injury risk. Collecting detailed biomechanical data is an arduous task. Identifying a relationship using more easily measured variables, such as quadriceps strength, would offer value for athlete counseling and injury prevention programs. Although quadriceps weakness has been associated with altered landing strategies in ACL-reconstructed (ACLR) individuals, this relationship is less clear in healthy athletes. Purpose: To investigate the association between isokinetic quadriceps strength and peak knee flexion angle during a vertical drop jump in healthy adolescent athletes. Study Design: Secondary analysis of previously collected data. Methods: Healthy adolescent athletes had their dominant leg quadriceps strength measured using an isokinetic dynamometer at 60{degrees}/s from 0-90{degrees} of knee flexion. Landing mechanics were assessed during a vertical drop jump using three-dimensional motion capture synchronized with force plates. Pearson correlation was used to evaluate the association between quadriceps strength and peak knee flexion angle during landing, with statistical significance defined as p < .05. Results: There was a weak negative correlation between quadriceps strength and peak knee flexion angle (p = .017, R = -.22 [-.04, -.38]), suggesting that stronger athletes achieved greater knee flexion angles. Discussion: Greater quadriceps strength was associated with increased peak knee flexion angles during landing; however, the weak correlation suggests that strength explains only a small portion of the variability in landing mechanics. These findings deviate slightly from prior literature in healthy populations but are consistent with studies demonstrating that greater quadriceps strength is associated with achieving greater peak knee flexion in ACLR patients. Accordingly, quadriceps strengthening should remain a key component of multifactorial ACL injury prevention programs.

Biomechanics studies using traditional optical motion capture have been limited by small, homogeneous sample sizes and a focus on single movements, restricting the ability to capture clinically relevant adaptations across daily tasks. These limitations are particularly consequential in heterogeneous musculoskeletal conditions such as knee osteoarthritis (OA), where variability in demographic and clinical characteristics necessitates large, representative samples to identify patient-specific biomechanical intervention targets. Markerless motion capture enables faster, high-throughput data collection and offers the potential for community-based assessments; however, its feasibility of use in clinical populations across diverse tasks remains unclear. This study evaluated the feasibility of community-based, high-throughput markerless biomechanics data collection in individuals with knee OA. Participants (n = 85) completed a series of activities of daily living using a portable markerless motion capture system deployed across two community-based and two on-campus sites. Feasibility was assessed using timing metrics related to research operations (transit, setup, calibration, breakdown), participant workflow (consent, questionnaires, motion capture), and task-specific durations. No significant differences in timing metrics were observed across sites despite logistical and operational challenges. These findings support the feasibility of using high-throughput, community-based markerless motion capture and suggest a viable pathway for addressing long-standing limitations in sample size and representativeness through scalable data collection workflows in biomechanics studies.

BackgroundExplosive force generation during the initial acceleration phase is critical for successful base stealing in baseball. Preparatory balance control preceding movement onset may facilitate this process by constraining horizontal ground reaction force (GRF) toward a task-specific direction. However, its contribution to ballistic sprint initiation remains unclear. Research questionDoes preparatory force constraint influence explosive force generation during base stealing, and when during the preparatory phase is this influence greatest? MethodsFourteen baseball players performed 3-m maximal sprints simulating base stealing under time-constraint (Time) and self-paced (Self) conditions. GRF around movement onset were recorded. Peak rate of force development (peak RFD) was computed from onset to take-off. A 250-ms window before the onset was divided into 50-ms bins, and mean resultant length (Rlen), which represents the extent of force constraint, of each bin was calculated. Using statistics analyses, Differences between conditions were tested, and the relationship between the interaction (Rlen x condition) and peak RFD was assessed. ResultsThe peak RFD was greater under the Self condition than under the Time condition, accompanied by a larger Rlen. Furthermore, Results indicated that the force constraint in the 150-100 ms interval preceding the movement onset most strongly influenced the peak RFD. SignificanceThese findings demonstrate that temporally organized preparatory force constraint plays a critical role in explosive sprint initiation during base stealing. Identifying the specific preparatory timing linked to superior force production provides novel mechanistic insight into preparatory balance control and may inform targeted training strategies for ballistic athletic movements.

Pedalling cadence during an acute eccentric cycling exercise altered physiological and perceptual responses. We examined the influence of cycling cadence on neuromuscular adaptation induced by a 6-week eccentric cycling training period. Eighteen participants performed training (eighteen sessions) at a cadence of 30 or 60 rpm over six weeks. Power output was the same between the two groups. Perceived effort and heart rate were recorded at each training session. Muscle pain and fatigue were reported the day after each session. Maximal voluntary contractions torque, as well as concentric and eccentric cycling efficiency, were assessed before and after training. Additionally, the loss of maximal voluntary isometric torque was assessed after the first and last training sessions. Heart rate and perceived effort increased in the second week of training and then plateaued, with no difference between groups. Muscle pain and fatigue remained low throughout the training, with no difference between groups. Isometric (+28%) and eccentric (+13%) maximal voluntary torque of knee extensor muscles increased regardless of training cadence. Concentric maximal voluntary torque increased for the group pedalling at 60 rpm only (+21%). Cycling efficiency was improved in eccentric mode only (+43%), with no difference between the two training groups. Finally, the voluntary isometric torque loss induced by the first and last sessions were similar. While six weeks of eccentric cycling training improved neuromuscular and functional capacities, cadence had no observable effect. This finding suggest that patients could choose their preferred cadence to obtain better adherence to the rehabilitation program without altering the adaptations.

Advanced footwear technology (AFT) has transformed competitive running, yet individual and sex-specific responses to different AFT models remain unclear, particularly near race pace. This study examined running economy (RE) and gait biomechanics in response to three top-tier AFT models (Shoe A: adidas Pro Evo 2; Shoe B: Nike Alphafly 3; Shoe C: On CloudBoom Strike 2) in 14 male and 12 female well-trained runners at sex-specific submaximal speeds (16 and 14 km{middle dot}h-{superscript 1}). RE, spatiotemporal, and joint kinematic/kinetic data were collected via indirect calorimetry, accelerometry, and three-dimensional motion capture with force platforms. RE was significantly lower in Shoe C than Shoe A (males: 2.1%; females: 1.4%) and Shoe B (males: 1.9%; females: 0.9%), with 73% of runners responding favourably to Shoe C, a more consistent response than previously reported. Despite being lightest, Shoe A produced the poorest RE, challenging conventional mass-economy assumptions. Biomechanically, Shoe C elicited greater impact magnitude, lower ankle quasi-stiffness, and greater ankle angular velocity during early stance. Female runners showed smaller RE improvements, potentially related to lower running velocity and body mass limiting midsole engagement. The most efficient AFT enabled these well-trained runners to be more spring-like through tolerating higher forces and faster angular velocities without greater demand on metabolic cost.

BackgroundThe pivot shift (PS) test is the most specific clinical examination for anterolateral rotational instability in ACL-deficient knees, yet grading remains subjective, as evidenced by poor inter-observer reliability, particularly for Grade 2. Since low-grade (Grade 1) versus high-grade (Grades 2/3) PS is the threshold for recommending lateral extra-articular augmentation, performing the test in awake clinic patients limits grading reproducibility and introduces variability in surgical decision-making. Existing methods to quantify the pivot shift usually require examiner-performed testing under general anaesthesia. No prior approach has ascertained PS grading from a separate patient-performed functional movement. PurposeTo evaluate the feasibility of a machine learning (ML) classifier, trained on kinematic ultrasound bone-tracking signals acquired during a patients sit-stand-sit (SSS) knee movement, to predict their PS grade, and to clinically validate its ability to differentiate low versus high-grade PS. MethodsUltrasound bone-tracking kinematic data were collected during SSS manoeuvres in 23 ACL-injured patients using the GATOR device, and ground truth PS grades (0-3) were assigned under general anaesthesia by fellowship-trained orthopaedic sports surgeons. From the data collected, Leave-one-out cross-validation (LOOCV) was used to train the ML classifier. Clinical SSS data from 6 ACL-deficient patients was used for independent held-out validation of their low-grade (Grade 1) versus high-grade (Grade 2/3) PS. Multiple deep learning architectures (XceptionTime, InceptionTime, FCN, ResNet, ResCNN) and training strategies (including mixup augmentation and supervised contrastive learning) were tested. Performance was measured by one-versus-rest (OVR) AUC under LOOCV and by AUC (low vs high grade PS) from the held-out patient sessions. ResultsThe ML classifier achieved a maximum OVR AUC of 0.928 {+/-} 0.084 under LOOCV. Classifier performance increased with pivot-shift severity: Grade 3 was identified most reliably (AUC ~0.81; sensitivity 0.70-0.80), whereas Grade 2 remained the most challenging boundary (sensitivity 0.20-0.75 across configurations). For the clinically relevant binary classification of low-versus high-grade pivot shift, the classifier generalised well to a completely unseen patient cohort (AUC 0.889; accuracy 0.860; sensitivity 0.850; minimum-class sensitivity 0.767). ConclusionThe study demonstrates that kinematic ultrasound bone-tracking during sit-stand-sit contains transferable information about rotational instability severity in ACL-deficient patients, and represents the first reported approach to predict pivot shift grade from a patient-performed functional movement. The strong cross-validation performance confirms that the signals contain meaningful PS grade-discriminative information, but larger datasets targeting 50-100 sessions per grade will be required to achieve patient-level generalisation and advance this novel rotational instability assessment tool toward full clinical adoption. Level of EvidenceLevel IV, diagnostic feasibility study.

This study aimed to investigate the test-retest reliability of the Jiu-Jitsu Anaerobic Performance Test (JJAPT), as well as its construct validity according to experience level (intermediate and advanced) and belt rank (blue, purple, brown, and black), in addition to its concurrent validity with physical performance measures. Twenty-three amateur Brazilian Jiu-Jitsu (BJJ) athletes participated in two assessment sessions. JJAPT repetitions (mean, peak, and total) were analyzed under 4 and 5-set protocols, along with physical tests including vertical jump, Wingate test, and specific strength-endurance tests. Reliability was assessed using the intraclass correlation coefficient (ICC), construct validity through t-tests and ANOVA, and concurrent validity through Pearsons correlation. Results indicated that the JJAPT showed moderate to good reliability (ICC = 0.74 to 0.82). No significant differences were observed between experience levels or belt ranks for any variables (p > 0.05), with trivial effect sizes, indicating a lack of discriminant validity. On the other hand, significant correlations were found between JJAPT performance and isometric and dynamic strength-endurance tests (r = 0.39 to 0.62), with moderate to large magnitudes. It is concluded that the JJAPT shows measurement stability; however, it demonstrates limited ability to discriminate performance between athletes of different experience levels and belt ranks, being more strongly associated with strength-endurance capacities. Keywords: Brazilian Jiu-Jitsu; anaerobic performance; training monitoring

This study examined the utility of HRV detrended fluctuation analysis alpha-1 (DFA1) to assess readiness-to-train and exercise durability under varying acute training loads. Nineteen trained cyclists completed two 20-minute time-trials (TT) under rested and fatigued conditions. DFA1 was measured during a standardized warm-up (WU), 20-min TT, and standardized cool-down (CD). Power output (PO) and DFA1 responses were compared across conditions, and associations with performance and fitness (W/kg) were examined. DFA1 values declined with increasing WU and CD exercise intensity (p<0.001) and were significantly attenuated following the 20-min TT (p<0.001). While DFA1 profiles did not differ significantly between rested and fatigued conditions, lower pre-TT DFA1 was associated with reduced TT performance (p=0.022; r=0.55), suggesting relevance to training readiness. Additionally, an 18% decline in DFA1 between 10- and 20-min during the TT (p=0.031), and lower post-TT values at matched intensities were observed (p<0.001), indicating physiological perturbation from the 20-min TT. Fitter participants exhibited lower DFA1 values during the 20-min TT (p<0.001; r=-0.77), suggesting a greater capacity to sustain physiological stress. While DFA1 is responsive to exercise intensity and stress, offering potential to assess training readiness and durability, more robust fatigue protocols are needed to validate DFA1 as training load monitoring tool.

ObjectivesTo determine whether early functional severity at presentation explains variability in return to sport (RTS) after ankle sprain in young athletes, compared with sprain subtype and injury mechanism. DesignRetrospective cohort study. MethodsAthletes aged [&le;]22 years with acute ankle sprains were identified from a prospectively maintained institutional database. Surgically treated cases were excluded. Functional severity at presentation was classified into three grades based on the ability to continue sports participation and ambulate immediately after injury. Injury mechanisms were categorized as high-energy deceleration (HED) or non-HED. RTS was analyzed as time to return and as prolonged RTS ([&ge;]4 weeks). Multivariable logistic regression was performed to identify factors independently associated with prolonged RTS. ResultsA total of 437 cases were included. Median RTS was 2.0 weeks (interquartile range, 0.0-4.0), and prolonged RTS occurred in 33.0% of cases. RTS duration increased stepwise with greater functional severity (p < 0.001). In multivariable analysis, functional severity was strongly associated with prolonged RTS (Grade 2: adjusted odds ratio [OR], 3.58; 95% confidence interval [CI], 2.07-6.19; Grade 3: adjusted OR, 24.53; 95% CI, 10.67-56.43; p < 0.001), and age was also independently associated (adjusted OR, 1.19 per year; 95% CI, 1.11-1.27; p < 0.001). Sprain subtype and injury mechanism were not independently associated with RTS after adjustment. ConclusionsEarly functional severity at presentation is the primary determinant of RTS after ankle sprain in young athletes. Apparent differences related to sprain subtype and injury mechanism are largely explained by initial functional impairment.

Gait asymmetry is a common manifestation of walking impairment among clinical populations. We recently developed a novel treadmill walking approach called dynamic treadmill walking that can provide asymmetric gait training by changing the treadmill speed between fast and slow speeds within a single stride. Here, we studied the energy expenditure associated with a variety of dynamic treadmill walking conditions. We hypothesized that the metabolic power required for dynamic treadmill walking in all conditions would approximate the metabolic power associated with conventional walking at the mean of the fast and slow speeds employed in the task. Eleven young adults without gait impairment walked on an instrumented treadmill and breathed into a metabolic measurement system. During dynamic treadmill walking, the treadmill fluctuated between 0.75m/s and 1.50m/s, each for 50% of an individuals stride time. We used a metronome to synchronize participants right heel-strikes with four different timing conditions. Net metabolic power during dynamic treadmill walking was significantly greater than normal walking at the mean speed of the task (1.125m/s) and generally lower than walking at the fast speed (1.5m/s). We did not observe any significant associations between net metabolic power and several measures of gait asymmetry during dynamic treadmill walking. These findings establish dynamic treadmill walking as a promising technique for improving gait symmetry in individuals who cannot tolerate fast treadmill walking, a common gait rehabilitation approach. Future work will assess the feasibility, metabolic demands, and clinical efficacy of using dynamic treadmill walking to improve gait symmetry in clinical populations. Key Points SummaryO_LIDynamic treadmill walking (i.e., walking with oscillating treadmill speeds) has previously been shown to drive gait asymmetries, but little is known about the energy expenditure required to complete the task. C_LIO_LIOur hypothesis was that dynamic treadmill walking would have similar metabolic power requirements to normal walking at a speed that is intermediate between the two dynamic treadmill walking speeds. C_LIO_LIWe found that dynamic treadmill walking actually requires metabolic power that is greater than the average of the two belt speeds, but less than that used for fast walking. C_LIO_LIDynamic treadmill walking is a promising and clinically translatable technique for rehabilitating populations with gait asymmetries that is not more energetically costly than fast treadmill walking, a common gait rehabilitation approach. C_LI

ObjectivesTo investigate the epidemiology of acute sports-related upper-extremity injuries in young athletes, with a particular focus on the frequency, anatomical distribution, injury types, and mechanisms of digit injuries. MethodsThis single-center retrospective observational study included athletes aged [&le;]22 years who sustained acute sports-related upper-extremity injuries between January 2017 and November 2025. Digit injuries were defined as injuries involving the thumb and fingers at or distal to the metacarpophalangeal joint. Injury characteristics, mechanisms, and sports categories were analyzed using descriptive statistics. ResultsA total of 1,219 acute sports-related upper-extremity injuries were analyzed. Digit injuries were the most common injury location, accounting for 412 cases (33.8%), followed by shoulder (30.7%), elbow (17.5%), wrist (14.4%), and palm injuries (3.6%). Jammed finger was the most frequent injury type, comprising 64.8% of digit injuries, followed by fractures (20.1%) and dislocations (5.3%). Most injuries were caused by contact mechanisms (90.3%), with ball contact being the predominant cause (49.5%). Ball sports accounted for 85.4% of all digit injuries. ConclusionsDigit injuries represent the most frequent acute sports-related upper-extremity injuries in athletes aged [&le;]22 years, with jammed finger accounting for the majority of cases. Most injuries were associated with ball contact, highlighting the need for preventive strategies and appropriate initial management for digit injuries in young athletes.

ObjectivesThis study aimed to compare exercise-induced changes in serum and salivary concentrations of cardiac troponin-I (cTnI) in athletes during and after a marathon. MethodsThirty-six male runners were recruited. Eighteen participants in group 1 completed a marathon (42.195 km), while eighteen participants in group 2 did not undergo this exercise. Blood and saliva samples were collected at twelve different time points and then analyzed for cTnI using an immunoassay. ResultsBiphasic cTnI release into the circulation was observed during and after the marathon. Moreover, a similar pattern of biphasic cTnI elevation was found in saliva. In group 1, salivary and serum concentrations of cTnI first peaked after 60 min of exercise (0.67{+/-}0.08 ng/mL and 0.76{+/-}0.07 ng/mL), decreased slightly towards the end of the marathon (0.40{+/-}0.06 ng/mL and 0.46{+/-}0.06 ng/mL), and then reached a second, higher peak 4 h post-exercise (0.72{+/-}0.09 ng/mL and 0.82{+/-}0.09 ng/mL), returning to baseline by 48 h after marathon completion (0.16{+/-}0.04 ng/mL and 0.18{+/-}0.04 ng/mL). In group 2, there were no time-dependent changes in cTnI concentrations in both saliva and serum. Deming regression and Passing-Bablok regression demonstrated that there was proportional agreement between salivary and serum levels of cTnI in both groups at all twelve time points. The Bland-Altman method revealed that there was a negative differential bias but no proportional bias in the data. ConclusionsDocumenting a similar, biphasic pattern of cTnI elevations in saliva and serum during and after the marathon provides a reliable non-invasive alternative without requiring a blood draw.

Background and Purpose: Walking after stroke is often characterized by persistent biomechanical impairments and reduced walking capacity. While visual biofeedback can improve gait mechanics and fast walking can enhance capacity, it is unclear whether individuals post-stroke can effectively use biofeedback at higher walking speeds to address both deficits simultaneously. This study examined the effects of walking speed on the ability of participants with chronic stroke to reduce step length (SL) errors using visual biofeedback. Methods: Sixteen individuals with chronic stroke walked on a treadmill at slow, self-selected, and fast speeds with and without visual SL biofeedback. Absolute SL error relative to individualized targets was calculated for paretic and non-paretic limbs. Linear mixed-effects models with piecewise linear splines assessed the effects of speed, limb, and feedback condition. Post hoc comparisons were performed for significant interactions. Results: At lower speeds, increasing speed reduced SL error in both limbs (p < 0.001). At higher speeds, the effects of speed were dependent on limb and condition (p < 0.001). Paretic SL error increased with speed without feedback but remained stable with feedback (p < 0.001). Non-paretic SL error decreased with speed regardless of condition. SL error was greater in the paretic limb overall (p < 0.001). Discussion and Conclusions: Fast walking alone did not reduce paretic SL errors. Participants with chronic stroke can effectively use visual biofeedback to reduce paretic SL errors at higher speeds, supporting its integration into high-intensity gait training to simultaneously treat biomechanical impairments and walking capacity deficits after stroke.

Purposeto characterize the dynamic postural control during weight load shifting with and without support surface reduction with temporal metrics commonly used in linear control systems identification. MethodsFrom the COP coordinates temporal, global and structural parameters were calculated. Reliability of derived parameters were determined using Bland-Altman analysis. ResultsFor the observed population, temporal variables tend to decrease when the complexity of the task is increased with the reduction in the support surface and the non dominance. ConclusionDelay and rise times were significantly shorter for the non-dominant limb in the anteroposterior direction when volunteers performed the same task with different limbs. In the mediolateral direction, delay and rise times were shorter in both unipodal stances with respect to their bipodal homologues. An increase in COP path length, velocity and sample entropy was observed when the support area was reduced. All parameters showed good reliability in both directions at all stances. This framework could be used in the clinical practice to assess dynamic postural control capabilities in patients whose balance is pathologically affected. The trial was evaluated and approved by the Central Committee of Bioethics in Biomedical Practice and Research of the province of Entre Rios.

High intensity and unaccustomed physical activity can induce skeletal muscle damage, while even routine movements can cause similar alterations in patients with neuromuscular disease. However, reliable assessment of muscle damage using indirect markers such as muscle function evaluation, invasive measurements, or imaging techniques is difficult to implement in routine clinical follow-up and sport field settings. Bioimpedance spectroscopy appears as a promising non-invasive, easy-to-use and transportable tool to assess indirect markers of muscle damage. The aim of this study was to determine whether bioimpedance spectroscopy data are sensitive to eccentric exercise-induced muscle damage and if these potential changes mirror responses in muscle function and tissue mechanical properties. Changes in knee extensors maximal isometric contraction torque, muscle soreness, resting rigidity of the quadriceps femoris muscle tissue, and bioimpedance parameters at rest and during maximal isometric contraction were assessed in nine healthy males before, immediately after and in the three days following 120 maximal isokinetic eccentric contractions. Maximal contraction torque was significantly reduced during the three days following the eccentric exercise (up to -24.2%) while muscle soreness and rigidity of the quadriceps femoris were elevated until the second day (+494.4% and +7.6%). Changes in bioimpedance spectroscopy parameters were transiently observed at rest immediately after the damaging exercise, but not in the days that followed. Although the changes in bioimpedance parameters correlated with that of the indirect markers of muscle damage, they had already returned to baseline while functional and mechanical impairments persisted. Therefore, bioimpedance spectroscopy measurements may represent a suitable and cost-effective means of monitoring muscle fatigue.