Comparative Effects of Complex Contrast Training and Traditional Training Methods on Physical Performance Within Female, Semiprofessional Australian Rules Football Players.

ABSTRACT: Luders, J, Garrett, J, Gleadhill, S, Mathews, L, and Bennett, H. Comparative effects of complex contrast training and traditional training methods on physical performance within female, semiprofessional Australian Rules Football players. J Strength Cond Res XX(X): 000-000, 2024-This study aimed to explore whether complex contrast training (CCT) would elicit greater strength and power adaptations than traditional (TRAD) training methods using a volume- and intensity-matched design. Fourteen semiprofessional female Australian Football players completed the study. Both CCT and TRAD saw improvements in all performance outcomes: 1 repetition maximum (1RM) back squat (21.3 ± 8.2 and 16.7 ± 6.8 kg), 1RM bench press (5.3 ± 3.6 and 2.1 ± 4.0 kg), 1RM trap bar deadlift (5.0 ± 6.6 and 11.3 ± 2.5 kg), 5 m sprint (0.002 ± 0.09 and 0.02 ± 0.2 s), 10 m sprint (0.04 ± 0.17 and 0.02 ± 0.1 s), 15 m sprint (0.009 ± 0.15 and 0.08 ± 0.2 s), countermovement jump (CMJ) height (230 ± 150 and 340 ± 390 cm), CMJ absolute peak power (158.5 ± 69.6 and 235.6 ± 229.6 N), CMJ relative peak power (3.46 ± 4.1 and 2.68 ± 1.4 N·kg-1)), and plyometric push-up peak relative power (20.5 ± 13.4 and 15.2 ± 13.5 N). There were no between-group differences except for TRAD recording slightly greater improvements in 1RM Trap bar deadlift (Bayes factor [BF10] = 1.210). Complex contrast training completed sessions on average ∼7 minutes quicker than TRAD (BF10 = 5.722), while both groups reporting similar ratings of perceived exertion (RPE) with CCT (±SD) 58.4 ± 6.7 minutes and TRAD 65.5 ± 4.8. Based on the results, CCT training provides the same performance outcomes as traditional training methods across a period of 8 weeks, while taking less time to achieve these outcomes and with similar RPE.

Changes in injury and illness incidence and burden in elite junior male Australian footballers over a 6-year period.

OBJECTIVES: The study aimed to determine a contemporary multi-year junior Australian football (AF) injury and illness profile and secondly, explore changes in incidence and burden over the six-year period. DESIGN: Prospective cohort study. METHODS: This study involved an elite male junior Under-18 competition and included six seasons of injury data between 2015 and 2021. A total of 1559 eligible players were included in the analysis. An injury was defined as 'any physical or medical condition that resulted in a player missing one or more regular competition season matches.' A Poisson regression model determined injury and illness incidence and burden across the league over a 6-year period and explored changes in injury incidence and burden over time. RESULTS: The frequency of injuries was 1023 over the six seasons. The most frequently reported injuries were ankle sprain or joint injuries (26.5 injuries/season), hamstring strains (15.8 injuries/season), and concussion (15.1 injuries/season). The most burdensome injuries were ankle sprain or joint injuries with 82.5 missed matches/season, followed by anterior cruciate ligament injuries with 53.7 missed matches/season and hamstring strains with 46.9 missed matches/season. Injury incidence did not change for the most common injury types over time (all p > 0.05). Injury burden significantly increased for concussions, ACL injuries, MCL injuries, and ankle sprain or joint injuries (all p < 0.05). CONCLUSIONS: The multi-year injury surveillance methodology identified injuries with the highest consistent incidence and those that caused the most burden to elite male junior AF players. The results can be used to reliably guide future injury prevention methodologies to reduce the impact on players and clubs.

The effect of individualised post-exercise blood flow restriction on recovery following strenuous resistance exercise: A randomised controlled trial.

The purpose was to clarify the effect of individualised post-exercise blood flow restriction (PE-BFR) on measures of recovery following strenuous resistance exercise. Twenty resistance-trained adults were randomised to a PE-BFR or control (CON) group and completed a fatigue protocol of five sets of 10 repetitions of maximal intensity concentric and eccentric seated knee extension exercise. Participants then lied supine with cuffs applied to the upper thigh and intermittently inflated to 80% limb occlusion pressure (PE-BFR) or 20 mmHg (CON) for 30 min (3 × 5 min per leg). Peak torque (PT), time-to-peak torque (TTP), countermovement jump height (CMJ), muscle soreness (DOMS) and perceived recovery (PR) were measured pre-fatigue, immediately post-fatigue and at 1, 24, 48 and 72 h post-fatigue. Using a linear mixed-effect model, PE-BFR was found to have greater recovery of CMJ at 48 h (mean difference [MD]=-2.8, 95% confidence interval [CI] -5.1, 0.5, p = 0.019), lower DOMS at 48 (MD = 3.0, 95% CI 1.2, 4.9, p = 0.001) and 72 h (MD = 1.95, 95% CI -1.2, 1.5, p = 0.038) and higher PR scores at 24 (MD = -1.7, 95% CI -3.4, -0.1, p = 0.038), 48 (MD = -3.1, 95% CI -4.8, -1.5, p < 0.001) and 72 h (MD = -2.2, 95% CI -3.8, -0.5, p = 0.011). These findings suggest that individualised PE-BFR accelerates recovery after strenuous exercise.

Ankle sprain, concussion, and anterior cruciate ligament injuries are common and burdensome in sub-elite female Australian football players.

OBJECTIVES: To describe the epidemiology of injuries in sub-elite female Australian Football (AF). DESIGN: Prospective cohort. METHODS: 424 athletes were tracked across a 12-match season. Injury characteristics (location, severity, mechanism) were reported. Injury incidence (injuries per 1000 h) and injury burden (days absent per 1000 h) were calculated. Severity was considered as the number of days missed between injury onset and return to full training. Incidence was compared using incidence rate ratios, and severity using a Mann-Whitney U test. RESULTS: Total injury incidence was 10.8 (95 % confidence interval [CI] = 9.0, 12.8) injuries per 1000 h. Match incidence was 34.6 (95 % CI = 28.0, 42.4) injuries per 1000 h. Ankle sprain injuries (2.2 per 1000 h, 95 % CI = 1.4, 3.1) and concussion (1.6 per 1000 h, 95 % CI = 1.0, 2.5) injuries were the most frequent, followed by anterior cruciate ligament (ACL) injuries (0.9 per 1000 h, 95 % CI = 0.4, 1.6). ACL (40.4 days per 1000 h, 95 % CI = 36.9, 44.1), ankle sprain injuries (31.4 per 1000 h, 95 % CI =28.4, 34.7), and concussion (19.9 per 1000 h, 95 % CI = 17.5, 22.5) injuries were also the most burdensome. There were 78 mild, 34 moderate, and 21 severe injuries. ACL injuries were the most severe injury (56.0 [77.0] in-season days missed). CONCLUSIONS: This research describes the first large-scale injury profile of sub-elite female AF, reporting time-loss measures of incidence and burden for many injury types. Ankle sprain injuries, concussions, and ACL injuries are common and burdensome, and should be prioritised for prevention.

Musculoskeletal model degrees of Freedom: Frontal plane constraints are hindering our understanding of human movement.

Induced acceleration analyses have expanded our understanding on the contributions of muscle forces to center of mass and segmental kinematics during a myriad of tasks. While these techniques have identified a subset of major muscle that contribute to locomotion, most analyses have included models with only one frontal plane degree of freedom (dof) actuated by the hip joint. The purpose of this study was to define the impact of including knee and subtalar joint frontal plane dof on model superposition accuracy and muscle specific contributions to mediolateral accelerations. Induced acceleration analyses were performed using OpenSim with the Lai model on a freely available dataset of one subject running at 4 m/s. Analyses were performed on four models (standard, with subtalar joint, with frontal plane knee, and combined frontal plane knee with subtalar) with the kinematic constraint and perturbation analyses. Root mean square error and correlations were computed against experimental kinematics. Adding frontal plane dofs improved mediolateral acceleration correlations on average by > 0.25 while only minimally impacting errors. The constraints method performed better than the perturbation method for mediolateral accelerations. Including frontal plane knee dof resulted in muscle and method specific responses. All muscles presented with a complete flip of polarity for constraint method, imparted by allowing the medial/lateral muscles to contribute according to their anatomical function. Only the gluteus medius flipped for the perturbation method. This study provides significant support for the inclusion of frontal plane knee and subtalar dof and the need for reevaluation of muscle contributions via induced acceleration.

Dose-Response Effect of an Inertia Flywheel Postactivation Performance Enhancement Protocol on Countermovement Jump Performance.

The purpose of this study was to investigate the dose-response effect of a high-load, 6-repetition, maximum effort inertial flywheel (IFw) squat postactivation performance enhancement (PAPE) protocol on countermovement jump (CMJ) performance metrics. Thirteen subjects completed 5 squat testing sessions: 1 session to determine back-squat 6-repetition maximum, 1 session to determine 6-repetition maximum IFw load, and 3 sessions to investigate the dose-response effect of an IFw PAPE protocol set at the load determined in the second session. In the IFw PAPE sessions, subjects completed either 1, 2, or 3 sets of IFw squats, then performed 5 CMJs over 12 minutes (1, 3, 6, 9, and 12 min post-IFw). All CMJ tests were conducted on a force platform where CMJ performance outcomes and impulse variables were calculated. There was no main time or volume effect for jump height, contact time, reactive strength index, peak force, or any of the impulse variables. A main time effect was identified for flight time (P = .006, effect size = 0.24) and peak power (P = .001, effect size = 0.28). The lack of change in jump height may indicate that too much fatigue was generated following this near-maximal IFw squat protocol, thereby reducing the PAPE effect.

Predicting Knee Joint Contact Forces During Normal Walking Using Kinematic Inputs With a Long-Short Term Neural Network.

Knee joint contact forces are commonly estimated via surrogate measures (i.e., external knee adduction moments or musculoskeletal modeling). Despite its capabilities, modeling is not optimal for clinicians or persons with limited experience. The purpose of this study was to design a novel prediction method for knee joint contact forces that is simplistic in terms of required inputs. This study included marker trajectories and instrumented knee forces during normal walking from the "Grand Challenge" (n = 6) and "CAMS" (n = 2) datasets. Inverse kinematics were used to derive stance phase hip (sagittal, frontal, transverse), knee (sagittal, frontal), ankle (sagittal), and trunk (frontal) kinematics. A long-short term memory network (LSTM) was created using matlab to predict medial and lateral knee force waveforms using combinations of the kinematics. The Grand Challenge and CAMS datasets trained and tested the network, respectively. Musculoskeletal modeling forces were derived using static optimization and joint reaction tools in OpenSim. Waveform accuracy was determined as the proportion of variance and root-mean-square error between network predictions and in vivo data. The LSTM network was highly accurate for medial forces (R2 = 0.77, RMSE = 0.27 BW) and required only frontal hip and knee and sagittal hip and ankle kinematics. Modeled medial force predictions were excellent (R2 = 0.77, RMSE = 0.33 BW). Lateral force predictions were poor for both methods (LSTM R2 = 0.18, RMSE = 0.08 BW; modeling R2 = 0.21, RMSE = 0.54 BW). The designed LSTM network outperformed most reports of musculoskeletal modeling, including those reached in this study, revealing knee joint forces can accurately be predicted by using only kinematic input variables.

Just Run: Development of a theory-based motivational online intervention for promoting ongoing running participation.

Running is a popular form of physical activity yet discontinuation is common. Interventions targeting physical activity adoption have shown modest effects, often with little translation into long-term participation, which may limit the health benefits available to the wider community. This paper details the development of a new online running intervention (Just Run) aimed at improving continuation of running activity in new runners through a motivational and psychological lens, including aspects of design, content, refinement, and usability testing. A six-step intervention mapping process was used to develop a theory-based online intervention using a mix of research designs. Key stakeholders including runners, coaches and relevant experts in physical activity and behavior change provided valuable insight, feedback and refinement of the education to be delivered. The final Just Run intervention included ten modules delivered online over twelve weeks to promote ongoing running participation through videos, testimonials, and activities. Key themes identified through the literature and stakeholder engagement process related to goal setting, self-efficacy, intrinsic motivation, social support and overcoming barriers to running participation. Usability testing confirmed the quality and suitability of the education to the target population. Just Run has been developed with a range of stakeholders to address an area of unmet need in the adoption and promotion of running. Just Run is a robust online intervention that has been designed and pre-tested with positive feedback and unique insights from key stakeholders. Further investigation is required to support its implementation to the wider community.

Evaluation of the Value of the Y-Balance Test to Predict Lower Limb Injuries in Professional Male Footballers.

CONTEXT: The aim of this prospective cohort study was to identify whether Y-Balance Test (YBT) performance and asymmetry are associated with lower limb injury in elite adult football athletes. DESIGN: A prospective cohort study. METHODS: Preseason YBT measures were obtained from 121 male footballers participating in National League One across the 2021-2022 season. Lower limb injuries were tracked across the season to determine the relationship between YBT variables and injury incidence using logistic regression analysis. The statistical significance level was .05. RESULTS: The average YBT score was 111.0 (5.8) cm on the left limb and 112.0 (5.5) cm on the right limb, with an average asymmetry of 2.3 (1.4) cm. Athletes with lower YBT scores on both the left (odds ratio = 2.9; 95% confidence interval, 1.7 to 4.8: P ≤ .001) and right (odds ratio = 2.3; 95% confidence interval, 1.6 to 3.2: P ≤ .001) limbs were at a greater risk of injury. Similarly, athletes with greater amounts of asymmetry were also more likely to get injured (odds ratio = 2.1; 95% confidence interval, 1.3 to 3.3: P = .002). CONCLUSIONS: Results indicate that lower and asymmetrical YBT scores have a significant relationship with future lower limb injuries in professional male footballers. The YBT offers a simple, reliable, and effective screening tool that can be used by practitioners in football to help identify players at a greater risk of injury before the season commences.

Rotation sequences for the calculation of shoulder kinematics of the volleyball attack.

Calculating upper extremity kinematics during overhead movements presents with problems typically not seen for the lower extremity due to the large range of motion. Due to these unique issues, different rotation sequences have been suggested to circumvent challenges due to gimbal lock (GL) and angle coherence (AC). The purpose of this study is to determine the most appropriate rotation sequence for shoulder angle calculation during a volleyball attack. METHODS: 15 healthy experienced volleyball players (women = 8) performed 5 attacks off a stationary ball. A 12-camera 3D motion capture system was utilized to record trunk and arm kinematics to compare joint angles calculated using the YXY, ZXY, XZY, YXZ, ZYX, and XYZ rotation sequences. Instances of GL and AC inconsistences were marked for each trial. The last 3 trials were used for analysis. RESULTS: The YXY and XYZ sequences presented with the least total number of errors (12 and 5, respectively). 5 instances of GL were present in the XYZ sequence while none were recorded for the YXY sequence. All other sequences returned incoherent angles that greatly exceeded known ranges of motion. CONCLUSION: When performing kinematic analyses during a volleyball attack, researchers should adhere to ISB recommendations and employ the Eulerian YXY sequence for calculations. If greater anatomical understanding is desired, the XYZ sequence may be utilized for most subjects.

Impact of Aerobic Training on Cardiovascular Function, Fitness, and Patient Reported Outcomes During Anthracycline Chemotherapy: A Case Series in Women With Breast Cancer.

BACKGROUND: Chemotherapy for breast cancer can increase the risk of cancer therapy related cardiac dysfunction (CTRCD). Exercise has been proposed to prevent CTRCD, however, research to date has indicated high degrees of individual variability following exercise interventions in this population. AIM: This study aimed to explore the impact of regular, individualized aerobic exercise on CTRCD incidence (defined by global longitudinal strain [GLS]) during and immediately upon the completion of dose-dense anthracycline (DDAC) chemotherapy in 5 women with breast cancer. METHODS: Five women receiving DDAC with stage I-III breast cancer enrolled. Participants underwent resting echocardiography and exercise testing before, during, upon the completion of, and 3 months after the completion of DDAC treatment to measure GLS and aerobic fitness (VO2peak). Participants opted-in to an individualized 8-week aerobic exercise intervention (3 sessions per week, 24 sessions total) or standard care for the duration of their DDAC treatment. Data for each participant were presented descriptively. RESULTS: Four of the 5 participants completed the exercise intervention during DDAC treatment (adherence 79.2%-91.7%). Mild asymptomatic CTRCD occurred in 2 of the 4 exercising participants, of whom both were at an increased risk (one was >65 years of age and diagnosed with hypertension, with the other receiving trastuzumab prior to DDAC treatment). Varied responses in VO2peak were observed and did not align with changes in GLS. The only participant not to complete the exercise intervention reported poorer health related quality of life and increased cancer related fatigue at all measurement timepoints. CONCLUSION: This study details the individual variability in cardiovascular responses to exercise that can occur during DDAC treatment in women with breast cancer, which can inform exercise professionals and researchers when designing individualized exercise programs for this population.

How do practitioners prescribe exercise to patients with breast cancer? Professional perspectives on the key considerations for aerobic exercise in patients with breast cancer undergoing chemotherapy.

OBJECTIVES: This study aimed to understand the key factors experienced accredited exercise physiologists (AEPs) and medical professionals consider when prescribing/recommending aerobic exercise to patients with breast cancer undergoing chemotherapy. DESIGN: Modified Delphi Survey. METHODS: A four-round, two-phase survey was conducted. Following a Delphi approach, four cancer-specific AEPs, four oncologists, and one breast cancer surgeon (median 13-yr breast-cancer-specific experience) completed phase one. Eighty-four AEPs (median 5-yr experience) completed phase two. Phase one participants answered open- and close-ended questions regarding key considerations for aerobic exercise in patients with breast cancer undergoing chemotherapy, and what information should be collected to guide exercise prescription. All questions and considerations agreed upon in phase one (>70 % rating 7-9 on a 0-9 Likert Scale) were rated by AEPs in phase two. RESULTS: Key considerations for exercise assessment and prescription aligned closely with exercise guidelines for cancer survivors. Common strategies for exercise individualisation were identified by AEPs, including separating aerobic exercise into 5-to--9-minute bouts when required and avoiding exercising to complete exhaustion. Exercise intensity and duration should be adjusted throughout chemotherapy to improve tolerance and adherence. Novel considerations for subjective questioning and objective assessments to tailor exercise prescription were outlined. CONCLUSIONS: This study identifies how professionals approach exercise assessment and prescription in patients with breast cancer undergoing chemotherapy. Findings can guide AEPs in practice when prescribing tailored exercise to breast cancer patients undergoing chemotherapy and inform future guidelines.

Effect of Aging on Movement Quality in Australian Urban Firefighters.

ABSTRACT: Redshaw, AS, Carrick-Ranson, G, Bennett, H, Norton, KI, and Walker, A. Effect of aging on movement quality in Australian urban firefighters. J Strength Cond Res 37(11): e601-e608, 2023-Adequate levels of movement quality (MQ) are required to safely perform occupational tasks in physically demanding and hazardous professions such as firefighting. Although it is well established that MQ deteriorates with age in population studies, there is conflicting evidence in older tactical populations. This study sought to examine the relationship between age and MQ in Australian urban firefighters. The impact of physical activity, injury history, and body mass index on MQ were also explored. The MQ of 324 professional Australian urban firefighters was assessed using MovementSCREEN MQ assessment tool. Scores of whole-body MQ ranged from 35.3 to 82.6 (0-100 scale), with a mean score of 59.2 ± 10.0. There was a moderate, negative association between MQ and age (r = -0.500; p ≤ 0.001), with those older than 50 years of age having significantly lower scores of MQ than their younger counterparts (p ≤ 0.001). Secondary analysis found that higher body mass index (r = -0.285; p ≤ 0.001), lower habitual physical activity levels (r = 0.165; p ≤ 0.003), and the presence of any musculoskeletal injury in the previous 12 months (p = 0.016) had significant negative effects on composite MQ. Firefighters older than 50, obese, and engaging in low levels of physical activity should be considered a high priority for functional strength training interventions to maintain adequate MQ throughout their careers.

Discrimination of cell-intrinsic and environment-dependent effects of natural genetic variation on Kupffer cell epigenomes and transcriptomes.

Noncoding genetic variation drives phenotypic diversity, but underlying mechanisms and affected cell types are incompletely understood. Here, investigation of effects of natural genetic variation on the epigenomes and transcriptomes of Kupffer cells derived from inbred mouse strains identified strain-specific environmental factors influencing Kupffer cell phenotypes, including leptin signaling in Kupffer cells from a steatohepatitis-resistant strain. Cell-autonomous and non-cell-autonomous effects of genetic variation were resolved by analysis of F1 hybrid mice and cells engrafted into an immunodeficient host. During homeostasis, non-cell-autonomous trans effects of genetic variation dominated control of Kupffer cells, while strain-specific responses to acute lipopolysaccharide injection were dominated by actions of cis-acting effects modifying response elements for lineage-determining and signal-dependent transcription factors. These findings demonstrate that epigenetic landscapes report on trans effects of genetic variation and serve as a resource for deeper analyses into genetic control of transcription in Kupffer cells and macrophages in vitro.

Human microglia maturation is underpinned by specific gene regulatory networks.

Microglia phenotypes are highly regulated by the brain environment, but the transcriptional networks that specify the maturation of human microglia are poorly understood. Here, we characterized stage-specific transcriptomes and epigenetic landscapes of fetal and postnatal human microglia and acquired corresponding data in induced pluripotent stem cell (iPSC)-derived microglia, in cerebral organoids, and following engraftment into humanized mice. Parallel development of computational approaches that considered transcription factor (TF) co-occurrence and enhancer activity allowed prediction of shared and state-specific gene regulatory networks associated with fetal and postnatal microglia. Additionally, many features of the human fetal-to-postnatal transition were recapitulated in a time-dependent manner following the engraftment of iPSC cells into humanized mice. These data and accompanying computational approaches will facilitate further efforts to elucidate mechanisms by which human microglia acquire stage- and disease-specific phenotypes.

Oxygen uptake and heart rate responses to 4 weeks of RPE-guided handcycle training.

PURPOSE: To investigate the efficacy of using Ratings of Perceived Exertion (RPE) to prescribe and regulate a 4-week handcycle training intervention. METHODS: Thirty active adults, untrained in upper body endurance exercise, were divided into three groups to complete a 4-week intervention: (i) RPE-guided training (n = 10; 2 female), (ii) power output (PO)-guided (n = 10; 2 female) training, or (iii) non-training control (n = 10; 4 female). Training groups performed three sessions of handcycling each week. Oxygen uptake ([Formula: see text]), heart rate (HR), and Feeling Scale (FS) rating were collected during training sessions. RPE-guided training was performed at RPE 13. PO-guided training was matched for percentage of peak PO per session, based upon that achieved by the RPE-guided training group. RESULTS: There were no differences in percentage of peak [Formula: see text] (66 ± 13% vs 61 ± 9%, p = 0.22), peak HR (75 ± 8% vs 71 ± 6%, p = 0.11) or FS rating (1.2 ± 1.9 vs 0.8 ± 1.6, p = 0.48) between RPE- and PO-guided training, respectively. The average coefficient of variation in percentage of peak HR between consecutive training sessions was 2.8% during RPE-guided training, and 3.4% during PO-guided training. CONCLUSION: Moderate-vigorous intensity handcycling exercise can be prescribed effectively using RPE across a chronic training intervention, suggesting utility for practitioners in a variety of rehabilitation settings.

A Comparison of Squat Depth and Sex on Knee Kinematics and Muscle Activation.

The squat is an essential exercise for strengthening lower body musculature. Although squats are frequently employed to improve lower extremity strength and neuromuscular control, differences between sexes and slight modifications, such as squat depth, can dramatically alter muscle recruitment and thus the foci of the exercise. The purpose of this study was to assess the effect of sex and squat depth on lower extremity coactivation and kinematics. Twenty recreationally active (female = 10) participants were recruited. The first visit consisted of one repetition maximum testing. For the second visit, muscle activation was recorded of the gluteus maximus (GM), semitendinosus, biceps femoris (BF), vastus medialis, vastus lateralis, rectus femoris, and gastrocnemius. Reflective markers were placed on the lower body for three-dimensional motion capture. Participants performed a series of squats to 90 deg knee flexion and 120 deg knee flexion. Benjamin-Hochberg procedure was employed and the alpha level was set at 0.05. Knee flexion (p < 0.001), adduction (p < 0.001), and external rotation (p = 0.008) were reduced during 90 deg compared to deep squats. Hip flexion, abduction, and external rotation were greater in deep squats (p < 0.001). Males had greater hip extensor to quad (HE:Q) cocontraction in 90 deg compared to deep squats (p = 0.007); females produced greater posterior chain activation in deep squats (p = 0.001) on ascent. When comparing sexes, males displayed greater HE:Q in the 90 deg squat during ascent (p = 0.013). The addition of deep squats into a preventative training program could be beneficial in reducing deficits prevalent in females and decrease injury incidence.

The impact of concussion on subsequent injury risk in elite junior Australian football athletes.

OBJECTIVES: Concussion increases injury risk. However, this has not been investigated in junior Australian football and it is unknown whether the location, severity, and mechanism of subsequent injuries differ after concussion vs. non-concussion injury. DESIGN: Prospective cohort. METHODS: 1455 elite adolescent male Australian footballers were tracked across seven seasons to determine whether subsequent injury risk was greater after concussion compared to non-concussion index injury using multilevel survival analysis. Mixed-effects logistic regression compared location and mechanism. Mixed-effects Poisson regression compared severity. RESULTS: Of 1455 athletes, 632 were injured and included in subsequent-injury analysis. There were no differences in injury incidence after a concussion compared to upper- (hazard ratio = 1.0, 0.6 to 1.9, P = 0.892; trivial effect) and lower (hazard ratio = 1.1, 0.6 to 1.9, P = 0.810; trivial effect) index injury, or in location. Subsequent injuries were more likely to be contact-based after a non-concussion injury than concussion (odds ratio = 4.6, 1.3 to 16.0; P = 0.017; large effect). There was no difference in subsequent injury severity after lower- (3.4 ±â€¯3.0 missed matches; incidence rate ratio = 1.4, 0.9 to 2.1; P ≤ 0.117; small effect) and upper-limb injuries (3.4 ±â€¯3.1 missed matches; incidence rate ratio = 1.4, 0.9 to 2.2; P = 0.189; small effect) compared to concussion (2.4 ±â€¯2.0 missed matches). CONCLUSIONS: Subsequent injury risk, severity, and location in junior Australian football are similar following concussion compared to non-concussion index injuries, although contact injuries are less likely.

Lower extremity joint stiffness of autistic adolescents during running at dual speeds.

Running is one of the most common forms of physical activity for autistic adolescents. However, research examining their lower extremity dynamics is sparse. In particular, no information exists regarding lower extremity joint stiffness in autistic adolescents. This study compared knee and ankle joint stiffness during the absorption phase of running between autistic adolescents and non-autistic controls. Motion capture and ground reaction forces were recorded for 22 autistic adolescents and 17 non-autistic age, sex, and BMI matched peers who ran at self-selected and standardized (3.0 m/s) speeds. Group × speed knee and ankle joint stiffness, change in moment, and range of motion were compared using mixed-model ANOVAs. There were no group × speed interactions for any variable. Autistic adolescents presented with significant (12 % and 19 %) reduced knee and ankle joint stiffness, respectively. In addition, autistic adolescents had significant reduced changes in knee and ankle joint moments by 11 % and 21 %, respectively, compared to their non-autistic peers. Only knee joint stiffness and knee joint moments were sensitive to running speed, each significantly increasing with speed by 6 %. Current literature suggests joint stiffness is an important mechanism for stability and usage of the stretch shortening cycle (or elastic recoil); as such, it is possible that the reduced ankle plantar flexor and knee extensor stiffness found in autistic adolescents in this study could be indicative of reduced efficiency during running. As group differences existed across both speeds, autistic adolescents may benefit from therapeutic and/or educational interventions targeting efficient running mechanics.