Sports Medicine

An eccentric contraction involves the active lengthening of muscle under an external load. The molecular and neural mechanisms underpinning eccentric contractions differ from those of concentric and isometric contractions and remain less understood. A number of molecular theories have been put forth to explain the unexplained observations during eccentric contractions that deviate from the predictions of the established theories of muscle contraction. Postulated mechanisms include a strain-induced modulation of actin-myosin interactions at the level of the cross-bridge, the activation of the structural protein titin, and the winding of titin on actin. Accordingly, neural strategies controlling eccentric contractions also differ with a greater, and possibly distinct, cortical activation observed despite an apparently lower activation at the level of the motor unit. The characteristics of eccentric contractions are associated with several acute physiological responses to eccentrically-emphasised exercise. Differences in neuromuscular, metabolic, hormonal and anabolic signalling responses during, and following, an eccentric exercise bout have frequently been observed in comparison to concentric exercise. Subsequently, the high levels of muscular strain with such exercise can induce muscle damage which is rarely observed with other contraction types. The net result of these eccentric contraction characteristics and responses appears to be a novel adaptive signal within the neuromuscular system.

The high forces undergone during repetitive eccentric, or lengthening, contractions place skeletal muscle under considerable stress, in particular if unaccustomed. Although muscle is highly adaptive, the responses to stress may not be optimally regulated by the body. Reactive oxygen species (ROS)are one component of the stress response that may contribute to muscle damage after eccentric exercise. Antioxidants may in turn scavenge ROS, thereby preventing or attenuating muscle damage. The antioxidant vitamins C (ascorbic acid) and E (tocopherol) are among the most commonly used sport supplements, and are often taken in large doses by athletes and other sportspersons because of their potential protective effect against muscle damage. This review assesses studies that have investigated the effects of these two antioxidants, alone or in combination, on muscle damage and oxidative stress. Studies have used a variety of supplementation strategies, with variations in dosage, timing and duration of supplementation. Although there is some evidence to show that both antioxidants can reduce indices of oxidative stress, there is little evidence to support a role for vitamin C and/or vitamin E in protecting against muscle damage. Indeed, antioxidant supplementation may actually interfere with the cellular signalling functions of ROS, thereby adversely affecting muscle performance. Furthermore, recent studies have cast doubt on the benign effects of long-term, high-dosage antioxidant supplementation. High doses of vitamin E, in particular, may increase all-cause mortality. Although some equivocation remains in the extant literature regarding the beneficial effects of antioxidant vitamin supplementation on muscle damage, there is little evidence to support such a role. Since the potential for long-term harm does exist, the casual use of high doses of antioxidants by athletes and others should perhaps be curtailed.

The purpose of this study was to investigate the relationships between lower limb and back injuries with perceived landing patterns and podiatric variables for injured and uninjured elite netball players. 228 players of a possible 240 participants at the 1988 Australian netball championships completed injury questionnaires and were assessed for injury status. Approximately 92% of those who were part of the injury surveys were also given a podiatric assessment. Pearson x2 and unpaired t-tests were used to assess relationships between injury status in 2 groups (history of injury, and injuries sustained during the championships) and perceived landing patterns during play and podiatric variables. A significant association was found between history of lower limb and back injuries and level of competition. Open age netballers reported more injuries than the younger players. During each championship, a similar number of players (23%) were injured irrespective of playing level. 71% of these players sustained a grade 1 injury, 15.4% a grade 2 injury and 13.5% presented with severe grade 3 injuries. 2 players were diagnosed with an anterior cruciate ligament injury and a further 3 players sustained a fracture during the championships. Most of the injuries were ligamentous (40.5%) with some overuse tendinitis (11.5%) problems. The injury history profiles of the elite players surveyed showed that ankle and knee injuries were the most common lower limb injuries with incidences of 58 and 22%, respectively. More than a quarter of the players had overuse type injuries (24% retropatellar pain, 38% shin soreness) and 33% complained of back problems during their careers. 18 significant relationships were found between injuries sustained during a player’s career and podiatric measures. Only 22.5% of a player’s foot types were classified as normal while 42% presented with rearfoot varus and 20% were grouped into pronated foot postures.

Several investigators have studied the incidence and causes of soccer injuries in male professional players; however, epidemiological data on injuries in female soccer players are limited. From the data presented, it can be estimated that, on average, every elite male soccer player incurs approximately one performance-limiting injury each year. Nine studies on the prevention of soccer injuries were found in the literature. There is some evidence that multi-modal intervention programmes result in a general reduction in injuries. Ankle sprains can be prevented by external ankle supports and proprioceptive/coordination training, especially in athletes with previous ankle sprains. With regard to severe knee injuries, the results of prevention studies are partly inconclusive; however, training of neuromuscular and proprioceptive performance as well as improvement of jumping and landing technique seem to decrease the incidence of anterior cruciate ligament injuries in female athletes. Prevention programmes are likely to be more effective in groups with an increased risk of injury. More methodologically well-designed studies are required to evaluate the effects of specific preventive interventions.

Recurrent peroneal tendon subluxation is an uncommon sports-related injury. The retrofibular groove is formed not by the concavity of the fibula itself, but by a relatively pronounced ridge of collagenous soft tissue blended with the periosteum that extends along the posterolateral lip of the distal fibula. The shape of the groove is primarily determined by this thick fibrocartilagenous periosteal cushion, and not by the bone itself. The superior peroneal retinaculum is extremely variable in width, thickness and insertional patterns. Peroneal tendon subluxation is commonly associated with longitudinal splits in the peroneus brevis tendon and lateral ankle instability. Disruption of the lateral collateral ankle ligaments places considerable strain on the superior peroneal retinaculum. This explains why the two conditions commonly coexist. In recurrent subluxation, patients usually give a history of previous ankle injury, which may have been misdiagnosed as a sprain. An unstable ankle that gives way or is associated with a popping or snapping sensation is another common complaint. The peroneal tendons may actually be seen subluxing anteriorly on the distal fibula during ambulation. The role of imaging has been debated, and the diagnosis and management plan are based on clinical evidence. Conservative management may be attempted in acute dislocations, operative management in athletes. Recurrent dislocations should be managed surgically. Five basic categories of repair have been described: (i) anatomical reattachment of the retinaculum; (ii) bone-block procedures; (iii) reinforcement of the superior peroneal retinaculum with local tissue transfers; (iv) rerouting the tendons behind the calcaneofibular ligament; and (v) groove deepening procedures. However, it is impossible to determine from the relatively small series which procedure is superior. If an anatomical approach to treating the pathology is utilised, reattachment of the superior retinaculum seems a most appropriate technique. Randomised controlled trials may be the way forward in determining the best surgical management method. However, the relative rarity of the condition and the large number of techniques described make such study difficult.

Research on the performance effects of acute carbohydrate supplementation is comprehensive. Here we present the first meta-analytic review of this research. Methods: Eighty-eight randomized crossover studies in which carbohydrate supplements were consumed with or without protein before and/or during exercise provided 155 estimates for performance effects in time-to-exhaustion tests or in time trials with or without a preload. For the mixed-model metaanalysis, all effects were converted into percentage changes in mean power in a non-preloaded time trial and weighted using percentage standard errors derived from exact p-values (in a minority of studies) or from estimated errors of measurement (in all other studies). Publication bias was assessed with a plot of t-values for the random-effect solutions versus standard errors. Probabilistic inferences were derived with reference to thresholds for small, moderate and large effects on performance of 0.5, 1.5 and 2.7%. Results: Publication bias was reduced by excluding studies with a standard error >1.25%. In the remaining 73 studies and 122 estimates, the meta-analysed performance effects of carbohydrate supplements ranged from clear large improvements of ~6% to clear moderate impairments of ~2%. The best supplement inferred from the analysis consisted of a ~3–10% carbohydrate plus-protein drink providing ~0.7 g/kg/h glucose polymers, ~0.2 g/kg/h fructose and ~0.2 g/kg/h protein. Substantial increases in the benefit of a supplement were probably small with an additional 9-hour fast and with the inclusion of ~0.2 g/kg/h of protein, probably small to moderate with ingesting the first bolus not at the start of exercise but 14 hours before exercise, and possibly small with increasing the frequency of ingestion by three boluses per hour. Substantial reductions in the benefit of a supplement were possibly moderate with a supplement providing >0.25 g/kg/h fructose, and possibly small with an increase in ambient temperature of 10°C. The effect in subjects with maximal oxygen consumption higher by 10mL/kg/min was probably trivial, and the effects of exercise duration were dependent on the concentration of carbohydrate plus protein in the supplement. The effect of including salt was unexpectedly trivial, and the effect of gender was unclear. Conclusions: Carbohydrate supplements with an appropriate composition and administration regimen can have large benefits on endurance performance. More research and better reporting are required to investigate the moderating effects of gender and salt.

The marked disparity in life expectancy between men and women suggests men are a vulnerable group requiring targeted health promotion programs. As such, there is an increasing need for health promotion strategies that effectively engage men with their health and/or illness management. Programs that promote physical activity could significantly improve the health of men. Although George et al. (Sports Med 42(3):281, 30) reviewed physical activity programs involving adult males published between 1990 and 2010, developments in men’s health have prompted the emergence of new sex- and gender-specific approaches targeting men. The purpose of this review was to: (1) extend and update the review undertaken by George et al. (Sports Med 42(3):281, 30) concerning the effectiveness of physical activity programs in males, and (2) evaluate the integration of gender-specific influences in the content, design, and delivery of men’s health promotion programs. A search of MEDLINE, CINAHL, ScienceDirect, Web of Science, PsycINFO, the Cochrane Library, and the SPORTDiscus databases for articles published between January 2010 and August 2014 was conducted. In total, 35 studies, involving evaluations of 31 programs, were identified. Findings revealed that a variety of techniques and modes of delivery could effectively promote physical activity among men. Though the majority of programs were offered exclusively to men, 12 programs explicitly integrated gender-related influences in male-specific programs in ways that recognized men’s interests and preferences. Innovations in male-only programs that focus on masculine ideals and gender influences to engage men in increasing their physical activity hold potential for informing strategies to promote other areas of men’s health.

Publication bias refers to a systematic deviation from the truth in the results of a meta-analysis due to the higher likelihood for published studies to be included in meta-analyses than unpublished studies. Publication bias can lead to misleading recommendations for decision and policy making. In this education review, we introduce, explain, and provide solutions to the pervasive misuses and misinterpretations of publication bias that afflict evidence syntheses in sport and exercise medicine, with a focus on the commonly used funnel-plot based methods. Publication bias is more routinely assessed by visually inspecting funnel plot asymmetry, although it has been consistently deemed unreliable, leading to the development of statistical tests to assess publication bias. However, most statistical tests of publication bias (i) cannot rule out alternative explanations for funnel plot asymmetry (e.g., between-study heterogeneity, choice of metric, chance) and (ii) are grossly underpowered, even when using an arbitrary minimum threshold of ten or more studies. We performed a cross-sectional meta-research investigation of how publication bias was assessed in systematic reviews with meta-analyses published in the top two sport and exercise medicine journals throughout 2021. This analysis highlights that publication bias is frequently misused and misinterpreted, even in top tier journals. Because of conceptual and methodological problems when assessing and interpreting publication bias, preventive strategies (e.g., pre-registration, registered reports, disclosing protocol deviations, and reporting all study findings regardless of direction or magnitude) offer the best and most efficient solution to mitigate the misuse and misinterpretation of publication bias. Because true publication bias is very difficult to determine, we recommend that future publications use the term “risk of publication bias”.