Biceps femoris long head muscle and aponeurosis geometry in males with and without a history of hamstring strain injury.

OBJECTIVES: Hamstring strain injuries (HSIs) commonly affect the proximal biceps femoris long head (BFlh) musculotendinous junction. Biomechanical modeling suggests narrow proximal BFlh aponeuroses and large muscle-to-aponeurosis width ratios increase localized tissue strains and presumably risk of HSI. This study aimed to determine if BFlh muscle and proximal aponeurosis geometry differed between limbs with and without a history of HSI. METHODS: Twenty-six recreationally active males with (n = 13) and without (n = 13) a history of unilateral HSI in the last 24 months underwent magnetic resonance imaging of both thighs. BFlh muscle and proximal aponeurosis cross-sectional areas, length, volume, and interface area between muscle and aponeurosis were extracted. Previously injured limbs were compared to uninjured contralateral and control limbs for discrete variables and ratios, and along the relative length of tissues using statistical parametric mapping. RESULTS: Previously injured limbs displayed significantly smaller muscle-to-aponeurosis volume ratios (p = 0.029, Wilcoxon effect size (ES) = 0.43) and larger proximal BFlh aponeurosis volumes (p = 0.019, ES = 0.46) than control limbs with no history of HSI. No significant differences were found between previously injured and uninjured contralateral limbs for any outcome measure (p = 0.216-1.000, ES = 0.01-0.36). CONCLUSIONS: Aponeurosis geometry differed between limbs with and without a history of HSI. The significantly larger BFlh proximal aponeuroses and smaller muscle-to-aponeurosis volume ratios in previously injured limbs could alter the strain experienced in muscle adjacent to the musculotendinous junction during active lengthening. Future research is required to determine if geometric differences influence the risk of re-injury and whether they can be altered via targeted training.

Vertical Jump Testing after Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis.

INTRODUCTION: Recently, there has been a call for vertical jump testing via force-plate analysis to be included in the assessment of individuals after anterior cruciate ligament reconstruction (ACLR) and as part of return-to-play criteria. However, a synthesis of current literature is needed to help guide clinicians on what tests to perform, which force-plate metrics to assess, and how these may change over the time course of rehabilitation. METHODS: Four online databases were searched from inception to July 2022. The Downs and Black checklist was used to assess study quality. Multilevel meta-analyses and meta-regressions were undertaken in conjunction with a best evidence synthesis. RESULTS: Forty-two articles were included, capturing 2375 participants with a history of ACLR. Reconstructed limbs displayed 1) lower peak eccentric forces, concentric forces, landing forces, and lower eccentric and concentric impulses (standardized means difference [SMD] = -1.84 to -0.46) than uninjured contralateral limbs during bilateral countermovement jumps (CMJ) and drop vertical jumps (DVJ); 2) lower jump heights and reactive strength indices (RSI), and longer contact times than uninjured contralateral limbs during unilateral CMJ and DVJ (SMD = -0.86 to 0.26); and 3) lower jump heights, RSI, and longer contact times during bilateral and unilateral CMJ, and unilateral DVJ, than uninjured controls (SMD = -1.19 to 1.08). Meta-regression revealed that time postsurgery was a significant moderator ( P < 0.05) for 1) bilateral CMJ height, peak concentric force, and peak landing force; 2) between-limb differences in unilateral CMJ height; and 3) differences in unilateral DVJ height, RSI, and contact time between reconstructed limbs and healthy controls with no history of injury. CONCLUSIONS: Individuals with a history of ACLR display chronic deficits in vertical jumping performance during a range of bilateral and unilateral tasks, which may have implications for return-to-play criteria and the design of interventions targeted at restoring long-term deficits in explosive lower limb strength after ACLR.

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.

Mechanical, Material and Morphological Adaptations of Healthy Lower Limb Tendons to Mechanical Loading: A Systematic Review and Meta-Analysis.

BACKGROUND: Exposure to increased mechanical loading during physical training can lead to increased tendon stiffness. However, the loading regimen that maximises tendon adaptation and the extent to which adaptation is driven by changes in tendon material properties or tendon geometry is not fully understood. OBJECTIVE: To determine (1) the effect of mechanical loading on tendon stiffness, modulus and cross-sectional area (CSA); (2) whether adaptations in stiffness are driven primarily by changes in CSA or modulus; (3) the effect of training type and associated loading parameters (relative intensity; localised strain, load duration, load volume and contraction mode) on stiffness, modulus or CSA; and (4) whether the magnitude of adaptation in tendon properties differs between age groups. METHODS: Five databases (PubMed, Scopus, CINAHL, SPORTDiscus, EMBASE) were searched for studies detailing load-induced adaptations in tendon morphological, material or mechanical properties. Standardised mean differences (SMDs) with 95% confidence intervals (CIs) were calculated and data were pooled using a random effects model to estimate variance. Meta regression was used to examine the moderating effects of changes in tendon CSA and modulus on tendon stiffness. RESULTS: Sixty-one articles met the inclusion criteria. The total number of participants in the included studies was 763. The Achilles tendon (33 studies) and the patella tendon (24 studies) were the most commonly studied regions. Resistance training was the main type of intervention (49 studies). Mechanical loading produced moderate increases in stiffness (standardised mean difference (SMD) 0.74; 95% confidence interval (CI) 0.62-0.86), large increases in modulus (SMD 0.82; 95% CI 0.58-1.07), and small increases in CSA (SMD 0.22; 95% CI 0.12-0.33). Meta-regression revealed that the main moderator of increased stiffness was modulus. Resistance training interventions induced greater increases in modulus than other training types (SMD 0.90; 95% CI 0.65-1.15) and higher strain resistance training protocols induced greater increases in modulus (SMD 0.82; 95% CI 0.44-1.20; p = 0.009) and stiffness (SMD 1.04; 95% CI 0.65-1.43; p = 0.007) than low-strain protocols. The magnitude of stiffness and modulus differences were greater in adult participants. CONCLUSIONS: Mechanical loading leads to positive adaptation in lower limb tendon stiffness, modulus and CSA. Studies to date indicate that the main mechanism of increased tendon stiffness due to physical training is increased tendon modulus, and that resistance training performed at high compared to low localised tendon strains is associated with the greatest positive tendon adaptation. PROSPERO registration no.: CRD42019141299.

Does isometric exercise result in exercise induced hypoalgesia in people with local musculoskeletal pain? A systematic review.

OBJECTIVE: The aim of this review was to investigate if exercise induced hypoalgesia (EIH) occurs following isometric muscle contraction in people with local musculoskeletal symptoms. DESIGN: Systematic review. DATA SOURCES: MEDLINE, EMBASE, CINAHL & SportDiscus electronic databases were searched (inception to April 2020). ELIGIBILITY CRITERIA: Two authors independently evaluated eligibility. Randomised controlled and crossover (repeated measures) trials that measured the effects of isometric exercise in participants with localised musculoskeletal pain during, and up to 2 hours after isometric exercise were included. Other inclusion criteria included comparison to another intervention, or comparison to healthy controls. Primary outcomes were experimentally induced pain thresholds and secondary outcomes included measures of pain sensitivity from clinical testing. RESULTS: 13 studies with data from 346 participants were included for narrative synthesis. EIH was reported in some upper and lower limb studies but there were no consistent data to show isometric exercises were superior to comparison interventions. CONCLUSION: There was no consistent evidence for EIH following isometric exercise in people with musculoskeletal pain. These findings are different to those reported in asymptomatic populations (where EIH is consistently demonstrated) as well as conditions associated with widespread symptoms such as fibromyalgia (where isometric exercise may induce hyperalgesia). Although well tolerated when prescribed, isometric exercise did not induce EIH consistently for people seeking care for local musculoskeletal symptoms. The variance in the dose, location of contraction and intensity of protocols included in this review may explain the inconsistent findings. Further work is required to better understand endogenous analgesia in musculoskeletal pain conditions.

The epidemiology of kicking injuries in professional Rugby Union: A 15-season prospective study.

PURPOSE: While kicking in Rugby Union can be influential to match outcome, the epidemiology of kicking injuries remains unknown. This study therefore aimed to investigate the epidemiology of injuries attributed to kicking in professional rugby, including playing position-specific effects and differences in kicking volumes and kick types. METHODS: Fifteen seasons of injury surveillance data and two seasons of match kicking characteristics from professional rugby players were analyzed. Incidence, propensity, and severity of kicking-related injuries were calculated together with the locations and types of these injuries. Position-related differences in match kicking types and volumes were also established. RESULTS: Seventy-seven match and 55 training acute-onset kicking injuries were identified. The match kicking injury incidence for backs was 1.4/1000 player-match-hours. Across all playing positions, the propensity for match kicking injury was 0.57 injuries/1000 kicks. Fly-halves sustained the greatest proportion of match kicking injuries (47%) and performed the greatest proportion of match kicks (46%); an average propensity for match kicking injury (0.58/1000 kicks). Scrum-halves executed 27% of match-related kicks but had a very low propensity for match kicking injury (0.17/1000 kicks). All other positional groups executed a small proportion of match-related kicks but a high propensity for match kicking injury. Ninety-two percent of match kicking injuries occurred in the pelvis or lower limb, with the majority sustained by the kicking limb. 21% of all match kicking injuries were associated with the rectus femoris muscle. CONCLUSION: Match kicking profiles and kicking injuries sustained are position-dependent, which provides valuable insight for developing player-specific conditioning and rehabilitation protocols.

Epidemiology of Injuries in West End Performers.

Epidemiological studies in the performing arts are scarce, and only one such study in the last 20 years directly examined West End productions. Therefore, the aim of this study was to analyze the epidemiology of injuries sustained by West End performers over a 12-month period (2016 to 2017). Injury data were self-reported retrospectively by West End performers using an online injury surveillance questionnaire. The information collected covered participant characteristics, injury location, diagnosis, severity, mechanism of injury, and external risk factors. Simple proportions were calculated for injury location and type. Categorical data were assessed using chi-squared (p = 0.05) and magnitude-based inferences described between-group differences. Forty-seven performers responded (26 male, 21 female), with 65% suffering at least one injury in the previous year. The lower limb accounted for 50% of injuries, and muscle strains were the diagnosis in 37% of cases. Males sustained 53% of all injuries, but no differences were found between sexes in locations injured (χ² = 2.296, p = 0.513). Seventy-two percent of injuries were said to have occurred during performance, with one-third of the total injuries having a gradual onset. Little or no time was lost in the majority of cases.