Peter Hamer

Evans Blue Dye as an in vivo marker of myofibre damage: optimising parameters for detecting initial myofibre membrane permeability

Evans Blue Dye (EBD) is widely used to study cellular membrane permeability and has recently been utilised in mdx mice to identify permeable skeletal myofibres that have become damaged as a result of muscular dystrophy. EBD has the potential to be a useful vital stain of myofibre permeability in other models of skeletal muscle injury and membrane‐associated fragility. The parameters for its use for such purposes were optimised in the present study. Of particular interest is the use of EBD to identify the onset of muscle damage. This study compared intravenous vs. intraperitoneal injection; tissue fixation; volume of EBD; time of availability in tissue; and persistence after injection in mdx mice (with endogenous muscle damage) and control mice. Satisfactory labelling of permeable myofibres was seen in frozen sections viewed with fluorescence microscopy when intraperitoneal injection of a 1% EBD solution injected at 1% volume relative to body mass was administered between 16 and 24 h prior to tissue sampling. EBD labelling was then assessed in three mouse models of experimental injury and repair – cut injury, whole muscle grafts, and exercise‐induced muscle damage. These experiments demonstrated that (i) following a cut injury across myofibres, EBD penetrated up to 150 µm from the injury site over a 20‐h period; (ii) EBD was present throughout myofibres of avascular whole muscle graft by one day after transplantation; and (iii) damaged myofibres were detected within 20 min after controlled lengthening–contraction exercise. This simple and inexpensive technique has sensitivity for the detection of increased myofibre permeability and/or sublethal damage that has advantages over other traditional histological techniques at the light microscopy level.

Sport, age, and sex specific incidence of sports injuries in Western Australia

Objective—To describe the trends in recreational sports injury in Perth, Western Australia. Design—A prospective cohort study of sports injuries during the 1997 winter season (May to September). Setting—Sample of Australian football, field hockey, basketball, and netball players from the Perth metropolitan area, Western Australia. Methods—A cohort of sports participants was followed over the five month winter sports season. Before the season, participants completed a baseline questionnaire and during the season were interviewed every four weeks by telephone. Results—Overall, 92% of participants (n = 1391) who completed a baseline questionnaire completed at least one follow up telephone interview. About half (51%) of the cohort sustained one or more injuries during the winter season accounting for a total of 1034 injuries. Most injuries were of moderate (58%, n = 598) or minor (40%, n = 412) severity, with only 3% (n = 24) requiring emergency department treatment or a hospital stay. The injury incidence rate was greatest for football (20.3/1000 hours of participation), similar for field hockey and basketball (15.2/1000 hours and 15.1/1000 hours respectively), and lowest for netball (12.1/1000 hours). The incidence of injury was greatest in the first four weeks of the season, and participants aged between 26 and 30 years had about a 55% greater risk of injury than those aged less than 18 years. Conclusions—This is one of the first studies to show that recreational sports are safe. Although the likelihood of injury was greatest in the first month of the season, few injuries required admission to hospital or emergency department treatment. A greater emphasis on prevention in the early part of the season should help to reduce the elevated incidence of injury found at this time.

The validity of a four week self-recall of sports injuries

The ability of sports injury studies to provide reliable incidence estimates depends on accurate injury data. One of the most commonly used methods of collecting injury data is through self-report, but the validity of such information is largely unknown. This study validated a four week self-report sports injury recall against a range of external sources including hospital records, health practitioner records, and third parties. Cases were drawn from the larger, Western Australian Sports Injury Study (WASIS). This study demonstrates acceptable to good levels of agreement between self-report and more objective data in relation to details such as the nature and body part injured, and the level of injury treatment sought (κ = 0.48 to 0.78). However, self-reported injury severity did not agree with the Injury Severity Score classification of severity.

Knee Strength and Knee Adduction Moments following Arthroscopic Partial Meniscectomy

PURPOSE This study investigated the relationship between muscular strength about the knee and knee joint moments during gait in patients who had undergone arthroscopic partial meniscectomy (APM). METHODS One hundred and two APM patients and 42 age-matched nonoperated controls underwent strength testing and three-dimensional gait analysis. Patients were divided into weak and normal subgroups and compared with controls for spatiotemporal, kinematic, and kinetic gait parameters. RESULTS Spatiotemporal parameters, kinematics, and sagittal plane kinetics were similar between APM patients and controls. The APM group displayed weaker concentric knee extension and flexion strength compared with controls. The weak APM subgroup had an increased average and peak knee adduction moments over stance compared with the APM subgroup with normal strength levels and controls. The normal strength APM subgroup had a larger peak knee adduction moment in early stance compared with controls. CONCLUSION Achieving normal lower limb muscle strength following APM appears important to resume normal frontal plane loading of the knee while walking.

Sports injury experiences from the Western Australian sports injury cohort study

Objective: The Western Australian Sports Injury Study is the first prospective cohort study of sports injuries sustained during community‐level sports participation in Australia.

The Recovery of Repeated-Sprint Exercise Is Associated with PCr Resynthesis, while Muscle pH and EMG Amplitude Remain Depressed

The physiological equivalents of power output maintenance and recovery during repeated-sprint exercise (RSE) remain to be fully elucidated. In an attempt to improve our understanding of the determinants of RSE performance we therefore aimed to determine its recovery following exhaustive exercise (which affected intramuscular and neural factors) concomitantly with those of intramuscular concentrations of adenosine triphosphate [ATP], phosphocreatine [PCr] and pH values and electromyography (EMG) activity (a proxy for net motor unit activity) changes. Eight young men performed 10, 6-s all-out sprints on a cycle ergometer, interspersed with 30 s of recovery, followed, after 6 min of passive recovery, by five 6-s sprints, again interspersed by 30 s of passive recovery. Biopsies of the vastus lateralis were obtained at rest, immediately after the first 10 sprints and after 6 min of recovery. EMG activity of the vastus lateralis was obtained from surface electrodes throughout exercise. Total work (TW), [ATP], [PCr], pH and EMG amplitude decreased significantly throughout the first ten sprints (P<0.05). After 6 min of recovery, TW during sprint 11 recovered to 86.3±7.7% of sprint 1. ATP and PCr were resynthesized to 92.6±6.0% and 85.3±10.3% of the resting value, respectively, but muscle pH and EMG amplitude remained depressed. PCr resynthesis was correlated with TW done in sprint 11 (r = 0.79, P<0.05) and TW done during sprints 11 to 15 (r = 0.67, P<0.05). There was a ∼2-fold greater decrease in the TW/EMG ratio in the last five sprints (sprint 11 to 15) than in the first five sprints (sprint 1 to 5) resulting in a disproportionate decrease in mechanical power (i.e., TW) in relation to EMG. Thus, we conclude that the inability to produce power output during repeated sprints is mostly mediated by intramuscular fatigue signals probably related with the control of PCr metabolism.

Incidence and risk factors for injury in non-elite Australian football

This paper identifies the risk and protective factors for injury in non-elite Australian Football. Five hundred and thirty five non-elite Australian footballers completed a baseline questionnaire at the commencement of the 1997 preseason. Participants were telephoned each month during the 1997 and 1998 playing seasons to provide details of their exposure at training and games and any injury experiences in the previous four weeks. The incidence of injury in this study was 24 injuries per 1000 player hours. The risk factors for injury were identified as: not wearing sports-specific football boots (IRR 1.40, 95% CI 1.03-1.90); an existing back pathology (IRR 1.29, 95% CI 1.10-1.51); excessive foot pronation (IRR 1.29, 95% CI 1.07-1.56); and extroverted behaviour (IRR 1.01, 95% CI 1.00-1.03). Cooling down after training (IRR 0.95, 95% CI 0.90-0.99) and not being injured in the previous 12 months (IRR 0.73, 95% CI 0.61-0.88) were found to be protective against injury. This study found that there was a high risk of injury associated with playing Australian Football at a community level. Further research is required to gain an understanding of the mechanisms by which the identified risk factors influence injury risk in community level Australian Football.

Neuromuscular adaptations to eccentric strength training in children and adolescents with cerebral palsy.

Aim  To determine the neuromuscular outcomes of an eccentric strength‐training programme for children and adolescents with cerebral palsy (CP).

Enhancing Muscular Qualities in Untrained Women: Linear versus Undulating Periodization

PURPOSE This study compared linear (LP) and undulating periodization (UP) on strength changes in untrained women when total workload and average training intensity were matched by the end of training. METHODS Twenty females (20 +/- 2 yr) were conditioned (3 wk) and assessed for one-repetition maximum squat (1RMSQ) and bench press (1RMBP) before being assigned to LP or UP training (9 wk), with training performed at 3 d.wk. Maximal strength, average power output during squat jumps with countermovement (SQJpwr) and bench press throws (BPTpwr), body mass, limb girth, and muscle cross-sectional area (CSA) were assessed at baseline (T1) and after every 3 wk (T2, T3, and T4) to differentiate the efficacy of LP and UP training. RESULTS Both groups improved significantly (P < 0.05) in 1RMSQ (LP 34.8%, UP 41.2%), 1RMBP (LP 21.8%, UP 28.3%), SQJpwr (LP 10.4%, UP 9.5%), BPTpwr (LP 11.1%, UP 13.8%), arm girth (LP 1.14%, UP 1.73%), and thigh girth (LP 1.58%, UP 1.99%), with no significant difference between them. Muscle CSA for the LP group increased significantly at T2 before maintaining similar hypertrophic responses until T4, whereas the UP group recorded significant increments from T1 to T2 and T2 to T3, before stabilizing between T3 and T4. Pooled CSA increase was higher than previously found (6.8% at T2, 11.3% at T3, and 11.8% at T4). CONCLUSIONS The comparison of LP and UP training with matched volume load and intensity suggests that both programs were equally adept in improving different strength qualities in active but untrained women. In addition, muscle hypertrophic responses were larger and occurred earlier than previously reported.

The Western Australian sports injury study

The magnitude and key risk and protective factors for sports injury at the population level in Australia have been established While rates of regular physical activity are increasing among Australians, there is potential for an increase in the number of injuries. It is important therefore to consider the benefits attributed to participation in sport and recreational pursuits in the light of the increased physical risks.1 Until now, there has been a lack of valid, reliable, and recent data on the incidence and up to date costs of sports injuries in Australia. Furthermore, much of the research has focused on elite participants,2 with a paucity of research among non-elite sports participants, despite the fact that most sports participants play at a non-elite level.3 As the risk of injury and the concomitant rate of injury are likely to be different in elite and non-elite sports participants, there was a need for research that could be translated into injury prevention policy and practice for non-elite sports participants. A proposal to establish the first Australian longitudinal population based study of sports injuries—the Western Australian sports injury study—was developed in collaboration with the peak non-government organisation for sports medicine in Australia—Sports Medicine Australia—and the authors. The broad aims of the study were to: The study was designed to provide information about a large number of sports participants and their resultant injuries. Although this approach limits the detailed examination of specific clinical, anthropometric, and biomechanical influences on injury, it was capable of quantifying the key risk and protective …