Perceptions of fatigue and neuromuscular measures of performance fatigability during prolonged low-intensity elbow flexions.

NEW FINDINGS: What is the central question of this study? What is the predictive relationship between self-reported scales to quantify perceptions of fatigue during exercise and gold standard measures used to quantify the development of neuromuscular fatigue? What is the main finding and its importance? No scale was determined to be substantively more effective than another. However, the number of ongoing contractions performed was shown to be a better predictor of fatigue in the motor system than any of the subjective scales. ABSTRACT: The purpose of this study was to determine the relationship between transcranial magnetic stimulation (TMS) measures of performance fatigability and commonly used scales that quantify perceptions of fatigue during exercise. Twenty healthy participants (age 23 ± 3 years, 10 female) performed 10 submaximal isometric elbow flexions at 20% maximal voluntary contraction (MVC) for 2 min, separated by 45 s of rest. Biceps brachii muscle electromyography and elbow flexion torque responses to single-pulse TMS were obtained at the end of each contraction to assess central factors of performance fatigability. A rating of perceived exertion (RPE) scale, Omnibus Resistance scale, Likert scale, Rating of Fatigue scale and a visual analogue scale (VAS) were used to assess perceptions of fatigue at the end of each contraction. The RPE (root mean square error (RMSE) = 0.144) and Rating of Fatigue (RMSE = 0.145) scales were the best predictors of decline in MVC torque, whereas the Likert (RMSE= 0.266) and RPE (RMSE= 0.268) scales were the best predictors of electromyographic amplitude. Although the Likert (RMSE = 7.6) and Rating of Fatigue (RMSE = 7.6) scales were the best predictors of voluntary muscle activation of any scale, the number of contractions performed during the protocol was a better predictor (RMSE = 7.3). The ability of the scales to predict TMS measures of performance fatigability were in general similar. Interestingly, the number of contractions performed was a better predictor of TMS measures than the scales themselves.

Shoulder pain and injury risk factors in competitive swimmers: A systematic review.

AIM: To synthesize and assess the literature for shoulder pain and injury risk factors in competitive swimmers. DESIGN: Systematic review with best-evidence synthesis. DATA SOURCES: CINHAL, SportDiscus, Scorpus, PubMed, and Embase databases from 1966 to April 30 2022. SEARCH AND INCLUSION: Cohort, cross-sectional, and case-control studies investigating shoulder pain or injury risk factors in competitive swimmers were included. Quality of eligible studies were assessed using a modified Newcastle-Ottawa scale. Risk factors were divided into four categories: modifiable-intrinsic, modifiable-extrinsic, non-modifiable, and other/secondary. RESULTS: Of 1356 studies identified, 24 full texts were evaluated for methodological quality, 22 met the criteria and were included in best evidence synthesis. There was no strong evidence supporting or refuting the association between 80 assessed variables and shoulder injury or pain. The swimmers' competitive level (nondirectional), and shoulder muscle recruitment profiles (e.g., increased activity of serratus anterior) exhibited moderate evidence supporting an association. Conversely, internal and external range of motion, middle finger back scratch test, training frequency, specialty stroke, height/weight, sex, and age all had moderate evidence opposing an association. Limited evidence was found for 58 variables, and conflicting for 8. The highest quality study (n = 201) suggested high acute-to-chronic workload ratio and reduced posterior shoulder strength endurance are associated with injury. CONCLUSIONS: Due to the paucity of high-quality studies, future prospective studies are needed to reevaluate known risk factor associations over exploring additional potential risk factors. Swimming practitioners should be aware of the nondirectional association of a swimmer's competitive level and pain, as squad changes could impact injury incidence. Moreover, swimmers experiencing shoulder pain may show increased activity in shoulder stabilizers during specific movements. Importantly, shoulder strength-endurance may be the most clinically relevant modifiable intrinsic risk factor.

Hamstring and knee injuries are associated with isometric hip and trunk muscle strength in elite Australian Rules and Rugby League players.

OBJECTIVES: This study investigated relationships between isometric trunk and hip extensor strength, lumbar muscle morphology, and the risk of hamstring and knee ligament injuries in Australian Football League and National Rugby League players. DESIGN: Prospective cohort study. METHODS: Trunk and hip extensor strength, multifidus and quadratus lumborum cross-sectional area were measured during the 2020 pre-season. Logistic regressions and decision trees were employed to explore associations between maximum strength, strength endurance, multifidus and quadratus lumborum cross-sectional area, age, previous injuries, and hamstring and knee ligament injury risk. RESULTS: Greater strength endurance [odds ratio = 0.42 (0.23-0.74), p = 0.004] and maximum strength [odds ratio = 0.55 (0.31-0.94), p = 0.039] reduced hamstring injury risk. Increased risk of knee ligament injuries was associated with larger multifidus [odds ratio = 1.66 (1.14-2.45), p = 0.008] and higher multifidus to quadratus lumborum ratio (odds ratio = 1.57 (1.13-2.23), p = 0.008]. Decision tree models indicated that low strength endurance (< 99 Nm) characterised hamstring strains, while high (≥ 1.33) multifidus to quadratus lumborum ratio mitigated risk. Knee ligament injuries were associated with larger (≥ 8.49 cm2) multifidus, greater (≥ 1.25) multifidus to quadratus lumborum ratio, and lower maximum strength (< 9.24 N/kg). CONCLUSIONS: Players with lower trunk and hip extensor maximum strength and strength endurance had increased risk of hamstring injuries, while knee ligament injury risk was elevated with larger multifidus cross-sectional area, higher multifidus to quadratus lumborum ratio, and lower maximum trunk and hip extensor strength.

Hamstring strain injury prevention: current beliefs and practices of practitioners working in Major League Baseball.

CONTEXT: Hamstring strain injuries (HSIs) are the most frequently sustained injury in Major League Baseball (MLB). However, the beliefs and practices of MLB practitioners regarding HSI risk factors and prevention strategies in baseball athletes, have not been documented. OBJECTIVE: To document the current beliefs and practices of MLB practitioners in relation to HSI prevention. DESIGN: cross-sectional study. SETTING: Major League Baseball via an online survey. PARTICIPANTS: Athletic trainers, physical therapists and strength and conditioning coaches employed in MLB during the 2021 season. DATA COLLECTION AND ANALYSIS: An online survey was conducted with participants completing the survey once. Questions pertained to risk factor identification, the use and perceived effectiveness of preventative strategies, and barriers to implementation. Descriptive statistics were calculated for each question. RESULTS: 91 responses were received featuring respondents from 28 of 30 MLB organizations. The perceived most important intrinsic risk factor for first-time HSI was tolerance to high-speed running and previous HSI for recurrent injury. The perceived most important extrinsic risk factor for both first-time and recurrent HSI was internal communication between staff.The perceived most effective prevention strategies were managing overall workload, exposure to high-speed running, and periodization. The most used prevention strategies were core/lumbopelvic strengthening, resistance training and workload management.Approximately half (53%) of respondents reported barriers to effective implementation of HSI prevention strategies, including player and coach buy-in, compliance, training time constraints, and in-season scheduling/reduced recovery time. CONCLUSIONS: This was the first survey to investigate MLB practitioner beliefs and practices regarding HSI prevention. Responses from practitioners regarding their beliefs about risk factors and appropriate prevention strategies were varied, and discrepancies existed between the perceived most effective strategies and those most frequently employed.

Proximity-to-goal as a constraint on patterns of behaviour in attacker-defender dyads in team games.

The aim of this study was to determine whether spatiotemporal interactions between footballers and the ball in 1 vs. 1 sub-phases are influenced by their proximity to the goal area. Twelve participants (age 15.3 ± 0.5 years) performed as attackers and defenders in 1 vs. 1 dyads across three field positions: (a) attacking the goal, (b) in midfield, and (c) advancing away from the goal area. In each position, the dribbler was required to move beyond an immediate defender with the ball towards the opposition goal. Interactions of attacker-defender dyads were filmed with player and ball displacement trajectories digitized using manual tracking software. One-way repeated measures analysis of variance was used to examine differences in mean defender-to-ball distance after this value had stabilized. Maximum attacker-to-ball distance was also compared as a function of proximity-to-goal. Significant differences were observed for defender-to-ball distance between locations (a) and (c) at the moment when the defender-to-ball distance had stabilized (a: 1.69 ± 0.64 m; c: 1.15 ± 0.59 m; P < 0.05). Findings indicate that proximity-to-goal influenced the performance of players, particularly when attacking or advancing away from goal areas, providing implications for training design in football. In this study, the task constraints of football revealed subtly different player interactions than observed in previous studies of dyadic systems in basketball and rugby union.

Thinking beyond impairment: Recommendations from contemporary models of care for working with children and disability.

BACKGROUND: The National Disability Insurance Scheme emphasises the use of models that move beyond an impairment focus to a holistic and individualised approach to disability. Application of specific biopsychosocial models supports general practitioners (GPs) to advance best practice in disability care within these schemes by meeting the complex care needs of their clients. OBJECTIVE: The aims of this article are to: 1) review current biopsychosocial models that underpin the health and functioning of children living with a disability in order to identify common elements of relevance to the paediatric sector, and 2) provide considerations for applying a biopsychosocial approach to paediatric care in practice. DISCUSSION: A succinct summary of common concepts within biopsychosocial models used in the paediatric setting, and recommendations for how these models can be best applied in practice, are presented in this article. The GP plays a crucial part in initiating and supporting children and adolescents who have complex care needs. Understanding these key concepts is fundamental to this process.

Predicting Noncontact Lower Limb Injury Using Lumbar Morphology in Professional Australian Football and Rugby League Players.

INTRODUCTION: Noncontact lower limb injuries are common within the Australian Football League (AFL) and National Rugby League (NRL). Smaller (<8.5 cm2) lumbar multifidus at the fifth vertebra (LM L5) and larger (>8.2 cm2) quadratus lumborum (QL) cross-sectional area (CSA) have been associated with increased noncontact lower limb injury risk in AFL players. These associations have not been explored in an NRL cohort. This study will attempt to replicate previous research findings by confirming that muscle morphology is associated with noncontact lower limb injury. METHODS: AFL (n = 87) and NRL (n = 151) players underwent LM L2-L5 and QL CSA ultrasound measures during preseason. Each club's medical staff reported all noncontact lower limb injuries sustained in the subsequent regular season. LM and QL CSA, age, body mass index, and noncontact lower limb injuries were analyzed using multivariable logistic regression. RESULTS: Seventy-two players sustained a noncontact lower limb injury in the 2020 regular season (AFL = 21, NRL = 51). The multivariable logistic regression (odds ratio (OR) = 1.36; 95% confidence interval (CI), 1.02-1.85; P = 0.038) identified AFL players with larger QL CSA at increased risk of sustaining a noncontact lower limb injury during the regular season, but no relationship was found for LM CSA and noncontact lower limb injuries in the AFL (OR = 1.01; 95% CI, 0.36-2.78; P = 0.591) or NRL (OR = 0.63; 95% CI, 0.29-1.33; P = 0.149). CONCLUSIONS: AFL players who sustained regular season noncontact lower limb injuries had larger QL CSA in preseason tests. No significant associations between either LM L5 CSA or LM L5 to QL ratio and regular season noncontact lower limb injuries were found.

Mechanism of Anterior Cruciate Ligament Loading during Dynamic Motor Tasks.

INTRODUCTION: This study determined anterior cruciate ligament (ACL) force and its contributors during a standardized drop-land-lateral jump task using a validated computational model. METHODS: Three-dimensional whole-body kinematics, ground reaction forces, and muscle activation patterns from eight knee-spanning muscles were collected during dynamic tasks performed by healthy recreationally active females (n = 24). These data were used in a combined neuromusculoskeletal and ACL force model to determine lower limb muscle and ACL forces. RESULTS: Peak ACL force (2.3 ± 0.5 bodyweight) was observed at ~14% of stance during the drop-land-lateral jump. The ACL force was primarily generated through the sagittal plane, and muscle was the dominant source of ACL loading. The main ACL antagonists (i.e., loaders) were the gastrocnemii and quadriceps, whereas the hamstrings were the main ACL agonists (i.e., supporters). CONCLUSION: Combining neuromusculoskeletal and ACL force models, the roles of muscle in ACL loading and support were determined during a challenging motor task. Results highlighted the importance of the gastrocnemius in ACL loading, which could be considered more prominently in ACL injury prevention and rehabilitation programs.

The availability of task-specific feedback does not affect 20 km time trial cycling performance or test-retest reliability in trained cyclists.

OBJECTIVES: This study examined the influence of the availability of task-specific feedback on 20 km time trial (20TT) cycling performance and test-retest reliability. DESIGN: Thirty trained, club-level cyclists completed two 20TT's on different days, with (feedback, FB) or without (no-feedback, NFB) task-specific feedback (i.e., power output, cadence, gear and heart rate [HR]). Elapsed distance was provided in both conditions. METHODS: During trials, ergometer variables and HR were continuously recorded, and a rating of perceived exertion (RPE) was collected every 2 km. Data were analysed using linear mixed-effects models in a Bayesian framework, and Cohen's d was calculated for standardised differences. The reliability of finish time and mean power output (PO) was determined via multiple indices, including intraclass correlations (ICC). RESULTS: Performance, pacing behaviour, and RPE were not statistically different between conditions. The posterior mean difference [95% credible interval] between TT1 and TT2 for FB and NFB was 10s [-5, 25] and -2s [-17, 14], respectively. In TT2, HR was statistically higher (∼8bmin-1) in FB compared to NFB after 13 km (d = 2.08-2.25). However, this result was explained by differences in maximal HR. Finish time (FB: ICC= 0.99; NFB: ICC=0.99) and mean power output (FB: ICC=0.99; NFB: ICC=0.99) in each condition were substantially reliable. CONCLUSIONS: The availability of task-specific information did not affect 20TT performance or reliability. Except for elapsed distance, task-specific feedback should be withheld from trained cyclists when evaluating interventions that may affect performance, to prevent participants from recalling previous performance settings.

Taekwondo Fighting in Training Does Not Simulate the Affective and Cognitive Demands of Competition: Implications for Behavior and Transfer.

Enhancing practice design is critical to facilitate transfer of learning. Considerable research has focused on the role of perceptual information in practice simulation, yet has neglected how affect and cognition are shaped by practice environments and whether this influences the fidelity of behavior (Headrick et al., 2015). This study filled this gap by examining the fidelity of individual (cognition, affect, and actions) and interpersonal behavior of 10 highly skilled Australian Taekwondo athletes fighting in training compared to competition. Interpersonal behavior was assessed by tracking location coordinates to analyze distance-time coordination tendencies of the fighter-fighter system. Individual actions were assessed through notational analysis and approximate entropy calculations of coordinate data to quantify the (un)predictability of movement displacement. Affect and cognition were assessed with mixed-methods that included perceptual scales measuring anxiety, arousal, and mental effort, and post-fight video-facilitated confrontational interviews to explore how affect and cognitions might differ. Quantitative differences were assessed with mixed models and dependent t-tests. Results reveal that individual and interpersonal behavior differed between training and competition. In training, individuals attacked less (d = 0.81, p < 0.05), initiated attacks from further away (d = -0.20, p < 0.05) and displayed more predictable movement trajectories (d = 0.84, p < 0.05). In training, fighters had lower anxiety (d = -1.26, p < 0.05), arousal (d = -1.07, p < 0.05), and mental effort (d = -0.77, p < 0.05). These results were accompanied by changes in interpersonal behavior, with larger interpersonal distances generated by the fighter-fighter system in training (d = 0.80, p < 0.05). Qualitative data revealed the emergence of cognitions and affect specific to the training environment, such as reductions in pressure, arousal, and mental challenge. Findings highlight the specificity of performer-environment interactions. Fighting in training affords reduced affective and cognitive demands and a decrease in action fidelity compared to competition. In addition to sampling information, representative practice needs to consider modeling the cognitions and affect of competition to enhance transfer.

Attunement to haptic information helps skilled performers select implements for striking a ball in cricket.

This study examined the perceptual attunement of relatively skilled individuals to the physical properties of striking implements in the sport of cricket. We also sought to assess whether utilizing bats with different physical properties would influence performance of a specific striking action: the front foot straight drive. Eleven skilled male cricketers (mean age = 16.6 ± 0.3 years) from an elite school cricket development program consented to participate in the study. While blindfolded, participants wielded six bats exhibiting different mass and moment of inertia (MOI) characteristics and were asked to identify the three bats they preferred the most for hitting a ball to a maximum distance by performing a front foot straight drive (a common shot in cricket). Next, participants actually attempted to hit balls projected from a ball machine using each of the six bat configurations to enable kinematic analysis of front foot straight drive performance with each implement. Results revealed that, on first choice, the two bats with the smallest mass and MOI values (1 and 2) were most preferred by almost two thirds (63.7 %) of the participants. Kinematic analysis of movement patterns revealed that bat velocity, step length, and bat-ball contact position measures significantly differed between bats. Data revealed how skilled youth cricketers were attuned to the different bat characteristics and harnessed movement system degeneracy to perform this complex interceptive action.