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Hopping, skipping, jumping and sprinting are common tasks in both active play and competitive sports. These movements utilise the stretch-shortening cycle (SSC), which is considered a naturally occurring muscle action for most forms of human locomotion. This muscle action results in more efficient movements and helps optimise relative force generated per motor unit recruited. Innate SSC development throughout childhood and adolescence enables children to increase power (jump higher and sprint faster) as they mature. Despite these improvements in physical performance, the underpinning mechanisms of SSC development during maturational years remain unclear. To the best of our knowledge, a comprehensive review of the potential structural and neuromuscular adaptations that underpin the SSC muscle action does not exist in the literature. Considering the importance of the SSC in human movement, it is imperative to understand how neural and structural adaptations throughout growth and maturation can influence this key muscle action. By understanding the factors that underpin functional SSC development, practitioners and clinicians will possess a better understanding of normal development processes, which will help differentiate between training-induced adaptations and those changes that occur naturally due to growth and maturation. Therefore, the focus of this article is to identify the potential underpinning mechanisms that drive development of SSC muscle action and to examine how SSC function is influenced by growth and maturation.

In 2013, the Oslo Sports Trauma Research Center Overuse Injury Questionnaire (OSTRC-O) was developed to record the magnitude, symptoms and consequences of overuse injuries in sport. Shortly afterwards, a modified version of the OSTRC-O was developed to capture all types of injuries and illnesses—The Oslo Sports Trauma Research Center Questionnaire on Health Problems (OSTRC-H). Since then, users from a range of research and clinical environments have identified areas in which these questionnaires may be improved. Therefore, the structure and content of the questionnaires was reviewed by an international panel consisting of the original developers, other user groups and experts in sports epidemiology and applied statistical methodology. Following a review panel meeting in October 2017, several changes were made to the questionnaires, including minor wording alterations, changes to the content of one question and the addition of questionnaire logic. In this paper, we present the updated versions of the questionnaires (OSTRC-O2 and OSTRC-H2), assess the likely impact of the updates on future data collection and discuss practical issues related to application of the questionnaires. We believe this update will improve respondent adherence and improve the quality of collected data.

Running economy (RE) has a strong relationship with running performance, and modifiable running biomechanics are a determining factor of RE. The purposes of this review were to (1) examine the intrinsic and extrinsic modifiable biomechanical factors affecting RE; (2) assess training-induced changes in RE and running biomechanics; (3) evaluate whether an economical running technique can be recommended and; (4) discuss potential areas for future research. Based on current evidence, the intrinsic factors that appeared beneficial for RE were using a preferred stride length range, which allows for stride length deviations up to 3 % shorter than preferred stride length; lower vertical oscillation; greater leg stiffness; low lower limb moment of inertia; less leg extension at toe-off; larger stride angles; alignment of the ground reaction force and leg axis during propulsion; maintaining arm swing; low thigh antagonist–agonist muscular coactivation; and low activation of lower limb muscles during propulsion. Extrinsic factors associated with a better RE were a firm, compliant shoe–surface interaction and being barefoot or wearing lightweight shoes. Several other modifiable biomechanical factors presented inconsistent relationships with RE. Running biomechanics during ground contact appeared to play an important role, specifically those during propulsion. Therefore, this phase has the strongest direct links with RE. Recurring methodological problems exist within the literature, such as cross-comparisons, assessing variables in isolation, and acute to short-term interventions. Therefore, recommending a general economical running technique should be approached with caution. Future work should focus on interdisciplinary longitudinal investigations combining RE, kinematics, kinetics, and neuromuscular and anatomical aspects, as well as applying a synergistic approach to understanding the role of kinetics.

Given the high rates of both primary and secondary anterior cruciate ligament (ACL) injuries in multidirectional field sports, there is a need to develop easily accessible methods for practitioners to monitor ACL injury risk. Field-based methods to assess knee variables associated with ACL injury are of particular interest to practitioners for monitoring injury risk in applied sports settings. Knee variables or proxy measures derived from wearable inertial measurement units (IMUs) may thus provide a powerful tool for efficient injury risk management. Therefore, the aim of this study was to identify whether there were correlations between laboratory-derived knee variables (knee range of motion (RoM), change in knee moment, and knee stiffness) and metrics derived from IMUs (angular velocities and accelerations) placed on the tibia and thigh, across a range of movements performed in practitioner assessments used to monitor ACL injury risk. Ground reaction forces, three-dimensional kinematics, and triaxial IMU data were recorded from nineteen healthy male participants performing bilateral and unilateral drop jumps, and a 90° cutting task. Spearman’s correlations were used to examine the correlations between knee variables and IMU-derived metrics. A significant strong positive correlation was observed between knee RoM and the area under the tibia angular velocity curve in all movements. Significant strong correlations were also observed in the unilateral drop jump between knee RoM, change in knee moment, and knee stiffness, and the area under the tibia acceleration curve (rs = 0.776, rs = −0.712, and rs = −0.765, respectively). A significant moderate correlation was observed between both knee RoM and knee stiffness, and the area under the thigh angular velocity curve (rs = 0.682 and rs = −0.641, respectively). The findings from this study suggest that it may be feasible to use IMU-derived angular velocities and acceleration measurements as proxy measures of knee variables in movements included in practitioner assessments used to monitor ACL injury risk.

Cricket was the first sport to publish recommended methods for injury surveillance in 2005. Since then, there have been changes to the nature of both cricket and injury surveillance. Researchers representing the major cricket playing nations met to propose changes to the previous recommendations, with an agreed voting block of 14. It was decided that 10 of 14 votes (70%) were required to add a new definition element and 11 of 14 (80%) were required to amend a previous definition. In addition to the previously agreed ‘Match time-loss’ injury, definitions of ‘General time-loss’, ‘Medical presentation’, ‘Player-reported’ and ‘Imaging-abnormality’ injuries are now provided. Further, new injury incidence units of match injuries per 1000 player days, and annual injuries per 100 players per year are recommended. There was a shift towards recommending a greater number of possible definitions, due to differing contexts and foci of cricket research (eg, professional vs amateur; injury surveillance systems vs specific injury category studies). It is recommended that researchers use and report as many of the definitions as possible to assist both comparisons between studies within cricket and with those from other sports.

Muscular coactivation can help stabilise a joint, but contrasting results in previous gait studies highlight that it is not clear whether this is metabolically beneficial. The aim was to assess the relationship between the metabolic cost of running and muscular coactivation across different running speeds, in addition to assessing the reliability and precision of lower limb muscular coactivation. Eleven female recreational runners visited the laboratory on two separate occasions. On both occasions subjects ran at three speeds (9.1, 11 and 12kmh−1) for six minutes each. Oxygen consumption and electromyographic data were simultaneously recorded during the final two minutes of each speed. Temporal coactivations of lower limb muscles during the stance phase were calculated. Five muscles were assessed: rectus femoris, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius lateralis. Nonparametric correlations revealed at least one significant, positive association between lower limb muscular coactivation and the metabolic cost of running for each speed. The length of tibialis anterior activation and muscular coactivation of the biceps femoris-tibialis anterior and gastrocnemius lateralis-tibialis anterior decreased with speed. These results show that longer coactivations of the proximal (rectus femoris-biceps femoris and vastus lateralis-biceps femoris) and leg extensor (rectus femoris-gastrocnemius lateralis) muscles were related to a greater metabolic cost of running, which could be detrimental to performance. The decrease in coactivation in the flexor and distal muscles at faster speeds occurs due to the shorter duration of tibialis anterior activation as speed increases, yet stability may be maintained.

ObjectivesFemale athletes engaging in high-impact sports have a higher prevalence of experiencing stress urinary incontinence (SUI). However, the prevalence of sport-specific SUI and associated risk factors in female rugby players is relatively unknown. We aimed to determine the prevalence of general and rugby-related SUI and identify associated risk factors and inciting events in female rugby players.MethodsObservational, cross-sectional study of 396 female rugby players (age 28±8 years, mass 80±18 kg, height 1.90±0.19 m, playing years 7±6 years) participating in rugby across UK and Ireland completed an electronic questionnaire regardless of SUI status.Results63 to 88% of players had SUI, and 43% had rugby-related SUI. There was an association with players reporting a change in incontinence status due to playing rugby (p<0.001). Players who experienced constipation (OR 2.33 (95% CI 1.49 to 3.66)), had given birth (OR 2.36 (95% CI 1.18 to 4.73)) or who had a higher body mass index (BMI) (OR 1.04 (95% CI 1.01 to 1.08)), were identified as having increased odds of rugby-related SUI. For rugby-specific risk factors, playing as a forward (OR 1.97 (95% CI 1.29 to 3.01)) increased the odds, whereas playing at a national compared with amateur level (OR 0.44 (95% CI 0.20 to 0.97)) decreased the odds of rugby-related SUI. The most prevalent inciting SUI events were being tackled (75%), tackling (66%), running (63%) and jumping/landing (59%).ConclusionRugby-related SUI was prevalent in female rugby players. Risk factors were having constipation, a high BMI, being postpartum, playing position and level. Player welfare strategies addressing pelvic floor dysfunction and postpartum rehabilitation are warranted.

Advances in medicine and public health initiatives have resulted in a health paradox: populations are living longer than ever before and the burden of chronic conditions such as cardiovascular disease, metabolic disorders, osteoarthritis and neurodegenerative illnesses continues to increase.1 In this issue of BJSM, the use of physical activity within this paradox will be examined, as we consider how physical activity can reduce and manage chronic illness, ultimately supporting healthy ageing in pursuit of both quantity and quality of life. The insights into physical activity in atrial fibrillation are expanded on in a systematic review and meta-analysis by Buckley and colleagues, focused on exercise-based cardiac rehabilitation for atrial fibrillation, demonstrating several benefits such as reduced symptom severity (see page 1242) . Health Benefits of Different Sports: a Systematic Review and Meta-Analysis of Longitudinal and Intervention Studies Including 2.6 Million Adult Participants.

Running biomechanics is considered an important determinant of running economy (RE). However, studies examining associations between running biomechanics and RE report inconsistent findings. The aim of this systematic review was to determine associations between running biomechanics and RE and explore potential causes of inconsistency. Three databases were searched and monitored up to April 2023. Observational studies were included if they (i) examined associations between running biomechanics and RE, or (ii) compared running biomechanics between groups differing in RE, or (iii) compared RE between groups differing in running biomechanics during level, constant-speed, and submaximal running in healthy humans (18-65 years). Risk of bias was assessed using a modified tool for observational studies and considered in the results interpretation using GRADE. Meta-analyses were performed when two or more studies reported on the same outcome. Meta-regressions were used to explore heterogeneity with speed, coefficient of variation of height, mass, and age as continuous outcomes, and standardization of running shoes, oxygen versus energetic cost, and correction for resting oxygen or energy cost as categorical outcomes. Fifty-one studies (n = 1115 participants) were included. Most spatiotemporal outcomes showed trivial and non-significant associations with RE: contact time r = - 0.02 (95% confidence interval [CI] - 0.15 to 0.12); flight time r = 0.11 (- 0.09 to 0.32); stride time r = 0.01 (- 0.8 to 0.50); duty factor r = - 0.06 (- 0.18 to 0.06); stride length r = 0.12 (- 0.15 to 0.38), and swing time r = 0.12 (- 0.13 to 0.36). A higher cadence showed a small significant association with a lower oxygen/energy cost (r = - 0.20 [- 0.35 to - 0.05]). A smaller vertical displacement and higher vertical and leg stiffness showed significant moderate associations with lower oxygen/energy cost (r = 0.35, - 0.31, - 0.28, respectively). Ankle, knee, and hip angles at initial contact, midstance or toe-off as well as their range of motion, peak vertical ground reaction force, mechanical work variables, and electromyographic activation were not significantly associated with RE, although potentially relevant trends were observed for some outcomes. Running biomechanics can explain 4-12% of the between-individual variation in RE when considered in isolation, with this magnitude potentially increasing when combining different variables. Implications for athletes, coaches, wearable technology, and researchers are discussed in the review. https://doi.org/10.17605/OSF.IO/293 ND (OpenScience Framework).

For these athletes and their multidisciplinary teams, the perinatal period provides challenges due to the complex changes to bodily systems.5 6 It is recommended that the following factors are considered within a whole-systems, biopsychosocial approach to perinatal athlete support: childbirth-related trauma (such as abdominal wall dysfunction, pelvic floor dysfunction or post-traumatic stress), menstrual health, breast health, energy balance, psychological well-being, fear of movement and sleep.5 6 Additionally, athletes should be supported in their choice to breastfeed, with consideration given to the physiological impact and practicalities surrounding breastfeeding with training and competition.5 Unlike musculoskeletal injury return-to-sport, pregnancy and childbirth offer athletes and their multidisciplinary teams a unique opportunity to plan ahead for the impending physical and psychological changes.9 This opportunity for forward planning calls for the development of athlete driven services to formulate proactive rather than reactive approaches to athlete care. The 6 Rs framework encourages practitioners to reframe perinatal athlete evaluation within a whole-systems, biopsychosocial model of care.5 It also supports a criterion-based approach3 to facilitate return to performance via individualised, evidence-informed, systematic and planned phases. Ready (prenatal—early postpartum) Ready the athlete for anticipated whole-systems, biopsychosocial changes* by proactively educating them about perinatal health considerations during the transition into pregnancy and motherhood (eg, weight gain, pelvic floor function, perinatal mental health). Refine Refine whole-systems, biopsychosocial strategies* (eg, optimise sleep quality, monitor for signs of relative energy deficiency syndrome) to enhance athlete training and competition availability, retaining the athlete in their sport and optimising performance.