Sports Medicine

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  1. Abstract

    A training plan, or an exercise prescription, is the point where we translate sport and exercise science into practice. As in medicine, good practice requires writing a training plan or prescribing an exercise programme based on the best current scientific evidence. A key issue, however, is that a training plan or exercise prescription is typically a mix of many interacting interventions (e.g. exercises and nutritional recommendations) that additionally change over time due to periodisation or tapering. Thus, it is virtually impossible to base a complex long-term training plan fully on scientific evidence. We, therefore, speak of evidence-informed training plans and exercise prescriptions to highlight that only some of the underlying decisions are made using an evidence-based decision approach. Another challenge is that the adaptation to a given, e.g. endurance or resistance training programme is often highly variable. Until biomarkers for trainability are identified, we must therefore continue to test athletes, clients, or patients, and monitor training variables via a training log to determine whether an individual sufficiently responds to a training intervention or else re-plan. Based on these ideas, we propose a subjective, pragmatic six-step approach that details how to write a training plan or exercise prescription that is partially based on scientific evidence. Finally, we advocate an athlete, client and patient-centered approach whereby an individual’s needs and abilities are the main consideration behind all decision-making. This implies that sometimes the most effective form of training is eschewed if the athlete, client or patient has other wishes.

  2. Abstract

    Return to play (RTP) criteria after hamstring strain injuries (HSIs) help clinicians in deciding whether an athlete is ready to safely resume previous sport activities. Today, functional and sport-specific training tests are the gold standard in the decision-making process. These criteria lead to an average RTP time between 11 and 25 days after a grade 1 or 2 HSI. However, the high re-injury rates indicate a possible inadequacy of the current RTP criteria. A possible explanation for this could be the neglect of biological healing time. The present review shows that studies indicating time as a possible factor within the RTP-decision are very scarce. However, studies on biological muscle healing showed immature scar tissue and incomplete muscle healing at the average moment of RTP. Twenty-five percent of the re-injuries occur in the first week after RTP and at the exact same location as the index injury. This review supports the statement that functional recovery precedes the biological healing of the muscle. Based on basic science studies on biological muscle healing, we recommend a minimum period of 4 weeks before RTP after a grade 1 or 2 HSI. In conclusion, we advise a comprehensive RTP functional test battery with respect for the natural healing process. Before deciding RTP readiness, clinicians should reflect whether or not it is biologically possible for the injured tissue to have regained enough strength to withstand the sport-specific forces. In an attempt to reduce the detrimental injury–reinjury cycle, it is time to start considering (biological healing) time.

  3. Abstract

    Background

    Sport-related head and neck injuries, including concussion, are a growing global public health concern with a need to explore injury risk reduction strategies such as neck exercises.

    Objectives

    To systematically review the literature to investigate: (1) the relationship between neck strength and sport-related head and neck injuries (including sport-related concussion (SRC); and (2) whether neck exercise programs can reduce the incidence of (a) sport-related head and neck injuries; and (b) SRC.

    Methods

    Five databases (Ovid MEDLINE, CINAHL, EMBASE, SPORTDiscus, and Web of Science) and research lists of included studies were searched using a combination of medical subject headings and keywords to locate original studies which reported the association between incidence of head and/or neck injury and neck strength data, or included a neck exercise intervention either in isolation or as part of a more comprehensive exercise program.

    Results

    From an initial search of 593 studies, six were included in this review. A narrative synthesis was performed due to the heterogeneity of the included studies. The results of two observational studies reported that higher neck strength, but not deep neck flexor endurance, is associated with a lower risk of sustaining a SRC. Four intervention studies demonstrated that injury reduction programs that included neck exercises can reduce the incidence of sport-related head and neck injuries including SRC.

    Conclusion

    Consideration should be given towards incorporating neck exercises into injury reduction exercise programs to reduce the incidence of sport-related head and neck injuries, including SRC.

    Systematic Review Registration

    PROSPERO (registration number: 194217).

  4. Abstract

    Background

    Perinatal growth abnormalities program susceptibility to childhood obesity, which is further exaggerated by maternal overweight and obesity (MO) during pregnancy. Exercise is highly accessible, but reports about the benefits of maternal exercise on fetal growth and childhood obesity outcomes are inconsistent, reducing the incentives for pregnant women to participate in exercise to improve children’s perinatal growth.

    Objective

    This systematic review and meta-analysis aims to establish evidence-based efficacy of exercise in mothers with normal weight (MNW) and MO during pregnancy in reducing the risks of perinatal growth abnormalities and childhood obesity. In addition, the impacts of exercise volume are also assessed.

    Methods

    The PubMed, ScienceDirect, Web of Science, and Cochrane Library databases were searched from inception to February 15, 2020. We included randomized controlled trials with exercise-only intervention or exercise with other confounders in pregnant MNW (body mass index, BMI 18.5–24.9 kg/m2) and MO (BMI ≥ 25 kg/m2), which were further subgrouped in the meta-analysis. Primary outcomes included birth weight, preterm birth, small for gestational age (SGA), large for gestational age (LGA), infant and childhood weight, and childhood obesity. A linear meta-regression analysis was also used to explore the effects of exercise volume on outcomes.

    Results

    99 studies were included in the meta-analysis (n = 596,876), and individual study quality ranged from fair to good according to the Newcastle–Ottawa scale assessment. Exercise only interventions in MNW reduced preterm birth by 15% (26 studies, n = 76,132; odds ratio [OR] 0.85; 95% CI 0.72, 1.01; I2 = 83.3%), SGA by 17% (33 studies, n = 92,351; OR 0.83; 95% CI 0.71, 0.98; I2 = 74.5%) and LGA by 17% (29 studies, n = 84,310; OR 0.83; 95% CI 0.74, 0.95; I2 = 60.4%). Exercise only interventions in MO reduced preterm birth by 33% (2 studies, n = 3,050; OR 0.67; 95% CI 0.70, 0.96; I2 = 0%), SGA by 27% (8 studies, n = 3,909; OR 0.73; 95% CI 0.50, 1.05; I2 = 40.4%) and LGA by 55% (9 studies, n = 81,581; OR 0.45; 95% CI 0.18, 1.11; I2 = 98.3%). Exercise only interventions in MNW reduced childhood obesity by 53% (3 studies, n = 6,920; OR 0.47; 95% CI 0.36, 0.63; I2 = 77.0%). However, no significant effect was observed in outcomes from exercise confounders in either MNW or MO. In the meta-regression, the volume of exercise-only intervention in MNW was negatively associated with birth weight, greatly driven by volumes more than 810 metabolic equivalents (MET)-min per week. Other outcomes were not associated with exercise volume.

    Conclusions

    This systematic review and meta-analysis suggests that exercise during pregnancy in both MNW and MO safely and effectively reduce the risks of preterm birth, SGA, and LGA. Furthermore, MNW exercise also reduces the risk of childhood obesity. Overall, regardless of prepregnancy BMI, maternal exercise during pregnancy provides an excellent opportunity to mitigate the high prevalence of adverse birth outcomes and childhood obesity.

  5. Abstract

    Background

    There is growing concern surrounding the role of repetitive sub-concussive head impacts, such as football heading, on brain health.

    Objectives

    Three questions were addressed while only considering studies that observed heading exposure directly: (1) how frequently does heading occur within football training and matches, (2) what are the biomechanical characteristics of heading, and (3) is cognitive function affected by heading?

    Methods

    This review followed the steps described in the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. Electronic databases including MEDLINE and SPORTDiscus were searched from the earliest entry to July 2020. Studies that reported independently quantified heading exposure, biomechanical characteristics of heading or the relationship between heading and cognitive function were included. Data were extracted and used to populate summary tables with reference to each research question.

    Results

    Heading incidence ranged between one to nine headers per player per match. The number of headers observed in small-sided games during training varied depending on the exact format used but generally speaking ranged between zero to one per player per game. The three most commonly reported biomechanical variables were head acceleration, head rotational velocity and overall movement kinematics during the heading action. Average head acceleration ranged from approximately four to 50 g. Nine out of 12 included studies did not observe a negative impact on cognitive test performance following exposure to heading and while three did, these negative effects were limited to specific outcome measures: reaction time and memory function.

    Conclusion

    The current weight of evidence summarised herein does not support the notion that heading is deleterious to cognitive performance in the short term; however, this conclusion is tentative due to methodological shortcomings in the existing evidence base.

  6. Abstract

    Background

    Concussion pre-injury (i.e., baseline) assessments serve as a benchmark comparison point in the event an individual sustains a concussion and allows clinicians to compare to post-injury measures. However, baseline assessments must reflect the individual’s true and most optimized performance to serve as a useful comparison. Mental fatigue and motivation throughout baseline testing may alter individual assessment performance, indicating an order of administration (OoA) may play an influential role in assessment outcomes.

    Objective

    To examine the influence concussion baseline battery OoA has on symptom, postural stability, cognitive screening, and computerized neurocognitive test outcomes.

    Methods

    We employed a retrospective observational cohort study to examine healthy collegiate student-athletes and military cadets (n = 2898, 19.0 ± 1.4 years, 66.1% male, 75.6% white, 54.4% Division-I) baseline assessment performance on the Sport Concussion Assessment Tool (SCAT; total symptom number and severity), Balance Error Scoring System (BESS; total error scores), Standardized Assessment of Concussion (SAC; total score), and Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) domain scores (verbal and visual memory, visual-motor speed, reaction time). Assessments were binned to beginning, middle, or end tertiles based upon OoA. We used one-way ANOVAs with Tukey post-hoc t tests, 95% confidence intervals (CI), and Cohen’s d effect sizes for significant models (α = 0.05).

    Results

    SCAT total symptom number (mean difference = 2.23; 95% CI 1.76–2.70; d = 0.49, p < 0.001) and severity (mean difference = 5.58; 95% CI 4.42–6.74; d = 0.50; p < 0.001) were lower when completed at the end of baseline testing compared to the middle. Total BESS errors were 1.06 lower when completed at the middle relative to the end (95% CI 0.43–1.69; d = 0.17; p = 0.001). Total SAC scores were better at the beginning relative to middle (mean difference = 0.58; 95% CI 0.25–0.90; d = 0.33; p < 0.001) and end (mean difference = 0.44; 95% CI 0.16–0.73; d = 0.24; p = 0.001). Verbal memory, visual memory, and reaction time performance were highest at the beginning (p ≤ 0.002), while visual-motor speed performance was highest at the middle (p = 0.001).

    Conclusion

    Completing baseline assessments in the order of (1) ImPACT, (2) SAC, (3) BESS, and (4) SCAT symptom checklist may improve performance across assessments collectively. Clinicians and researchers should consider completing baseline assessments in this order when possible to potentially aid in optimizing concussion baseline assessment performance and maximize post-concussion comparisons.

  7. Abstract

    Background

    The ergogenic effects of dietary supplements on endurance exercise performance are well-established; however, their efficacy in hot environmental conditions has not been systematically evaluated.

    Objectives

    (1) To meta-analyse studies investigating the effects of selected dietary supplements on endurance performance and core temperature responses in the heat. Supplements were included if they were deemed to: (a) have a strong evidence base for ‘directly’ improving thermoneutral endurance performance, based on current position statements, or (b) have a proposed mechanism of action that related to modifiable factors associated with thermal balance. (2) To conduct meta-regressions to evaluate the moderating effect of selected variables on endurance performance and core temperature responses in the heat following dietary supplementation.

    Methods

    A search was performed using various databases in May 2020. After screening, 25 peer-reviewed articles were identified for inclusion, across three separate meta-analyses: (1) exercise performance; (2) end core temperature; (3) submaximal core temperature. The moderating effect of several variables were assessed via sub-analysis and meta-regression.

    Results

    Overall, dietary supplementation had a trivial significant positive effect on exercise performance (Hedges’ g = 0.18, 95% CI 0.007–0.352, P = 0.042), a trivial non-significant positive effect on submaximal core temperature (Hedges’ g = 0.18, 95% CI − 0.021 to 0.379, P = 0.080) and a small non-significant positive effect on end core temperature (Hedges’ g = 0.20, 95% CI − 0.041 to 0.439, P = 0.104) in the heat. There was a non-significant effect of individual supplements on exercise performance (P = 0.973) and submaximal core temperature (P = 0.599). However, end core temperature was significantly affected by supplement type (P = 0.003), which was attributable to caffeine’s large significant positive effect (n = 8; Hedges’ g = 0.82, 95% CI 0.433–1.202, P < 0.001) and taurine’s medium significant negative effect (n = 1; Hedges’ g = − 0.96, 95% CI − 1.855 to − 0.069, P = 0.035).

    Conclusion

    Supplements such as caffeine and nitrates do not enhance endurance performance in the heat, with caffeine also increasing core temperature responses. Some amino acids might offer the greatest performance benefits in the heat. Exercising in the heat negatively affected the efficacy of many dietary supplements, indicating that further research is needed and current guidelines for performance in hot environments likely require revision.

  8. Abstract

    Lack of time is among the more commonly reported barriers for abstention from exercise programs. The aim of this review was to determine how strength training can be most effectively carried out in a time-efficient manner by critically evaluating research on acute training variables, advanced training techniques, and the need for warm-up and stretching. When programming strength training for optimum time-efficiency we recommend prioritizing bilateral, multi-joint exercises that include full dynamic movements (i.e. both eccentric and concentric muscle actions), and to perform a minimum of one leg pressing exercise (e.g. squats), one upper-body pulling exercise (e.g. pull-up) and one upper-body pushing exercise (e.g. bench press). Exercises can be performed with machines and/or free weights based on training goals, availability, and personal preferences. Weekly training volume is more important than training frequency and we recommend performing a minimum of 4 weekly sets per muscle group using a 6–15 RM loading range (15–40 repetitions can be used if training is performed to volitional failure). Advanced training techniques, such as supersets, drop sets and rest-pause training roughly halves training time compared to traditional training, while maintaining training volume. However, these methods are probably better at inducing hypertrophy than muscular strength, and more research is needed on longitudinal training effects. Finally, we advise restricting the warm-up to exercise-specific warm-ups, and only prioritize stretching if the goal of training is to increase flexibility. This review shows how acute training variables can be manipulated, and how specific training techniques can be used to optimize the training response: time ratio in regard to improvements in strength and hypertrophy.

    Graphic Abstract

  9. Abstract

    Background

    If interplanetary travel is to be successful over the coming decades, it is essential that countermeasures to minimize deterioration of the musculoskeletal system are as effective as possible, given the increased duration of spaceflight associated with such missions. The aim of this review, therefore, is to determine the magnitude of deconditioning of the musculoskeletal system during prolonged spaceflight and recommend possible methods to enhance the existing countermeasures.

    Methods

    A literature search was conducted using PubMed, Ovid and Scopus databases. 5541 studies were identified prior to the removal of duplicates and the application of the following inclusion criteria: (1) group means and standard deviations for pre- and post-spaceflight for measures of strength, muscle mass or bone density were reported (or provided by the corresponding author when requested via e-mail), (2) exercise-based countermeasures were included, (3) the population of the studies were human, (4) muscle function was assessed and (5) spaceflight rather than simulated spaceflight was used. The methodological quality of the included studies was evaluated using a modified Physiotherapy Evidence Database (PEDro) scale for quality, with publication bias assessed using a failsafe N (Rosenthal method), and consistency of studies analysed using I2 as a test of heterogeneity. Secondary analysis of studies included Hedges’ g effect sizes, and between-study differences were estimated using a random-effects model.

    Results

    A total of 11 studies were included in the meta-analyses. Heterogeneity of the completed meta-analyses was conducted revealing homogeneity for bone mineral density (BMD) and spinal muscle size (Tau2 < 0.001; I2 = 0.00%, p > 0.05), although a high level of heterogeneity was noted for lower body force production (Tau2 = 1.546; I2 = 76.03%, p < 0.001) and lower body muscle mass (Tau2 = 1.386; I2 = 74.38%, p < 0.001). The estimated variance (≤ -0.306) for each of the meta-analyses was significant (p ≤ 0.033), for BMD (− 0.48 to − 0.53, p < 0.001), lower body force production (− 1.75, p < 0.001) and lower body muscle size (− 1.98, p < 0.001). Spaceflight results in small reductions in BMD of the femur (Hedges g = − 0.49 [− 0.69 to – 0.28]), trochanter (Hedges g = − 0.53 [− 0.77 to – 0.29]), and lumbo-pelvic region (Hedges g = − 0.48 [− 0.73 to – 0.23]), but large decreases in lower limb force production (Hedges g = − 1.75 [− 2.50 to – 0.99]) and lower limb muscle size (Hedges g = − 1.98 [− 2.72 to – 1.23]).

    Conclusions

    Current exercise countermeasures result in small reductions in BMD during long-duration spaceflight. In contrast, such exercise protocols do not alleviate the reductions in muscle function or muscle size, which may be attributable to the low to moderate loads reported by crewmembers and the interference effect associated with concurrent training. It is recommended that higher-load resistance exercise and the use of high-intensity interval training should be investigated, to determine if such modifications to the reported training practices result in more effective countermeasures to the deleterious effect of long-duration spaceflight on the muscular system.

  10. Abstract

    Linear loading, the two-for-two rule, percent of one repetition maximum (1RM), RM zones, rate of perceived exertion (RPE), repetitions in reserve, set-repetition best, autoregulatory progressive resistance exercise (APRE), and velocity-based training (VBT) are all methods of adjusting resistance training intensity. Each method has advantages and disadvantages that strength and conditioning practitioners should be aware of when measuring and monitoring strength characteristics. The linear loading and 2-for-2 methods may be beneficial for novice athletes; however, they may be limited in their capacity to provide athletes with variation and detrimental if used exclusively for long periods of time. The percent of 1RM and RM zone methods may provide athletes with more variation and greater potential for strength–power adaptations; however, they fail to account for daily changes in athlete’s performance capabilities. An athlete’s daily readiness can be addressed to various extents by both subjective (e.g., RPE, repetitions in reserve, set-repetition best, and APRE) and objective (e.g., VBT) load adjustment methods. Future resistance training monitoring may aim to include a combination of measures that quantify outcome (e.g., velocity, load, time, etc.) with process (e.g., variability, coordination, efficiency, etc.) relevant to the stage of learning or the task being performed. Load adjustment and monitoring methods should be used to supplement and guide the practitioner, quantify what the practitioner ‘sees’, and provide longitudinal data to assist in reviewing athlete development and providing baselines for the rate of expected development in resistance training when an athlete returns to sport from injury or large training load reductions.

  11. Abstract

    Background

    The relationship between exercise-induced muscle damage (EIMD) indicators and acute training loads (TL) is yet to be reviewed extensively in semi-elite and elite athlete populations.

    Objectives

    The objectives of this systematic review and meta-analysis were threefold: (1) to evaluate studies of EIMD following the initial period of the preseason in semi-elite and elite athletes: (2) to examine acute physiological and performance responses across two periods of the season with similar TL; and (3) to examine acute physiological and performance responses to acute changes in TL during the season.

    Methods

    The CINAHL, PubMed, Scopus, SPORTDiscus and Web of Science databases were systematically searched for studies that investigated: (1) semi-elite or elite athletes in team or individual sports following a periodised training programme; and (2) measured acute responses to training. Studies were excluded if: (1) conducted in animals; (2) non-English language; or (3) a conference abstract, review or case report. The Kmet Quality Scoring of Quantitative Studies tool was used for study appraisal.

    Synthesis Methods

    Data were quantitatively analysed by generating forest plots to report test statistics for statistical significance and inter-trial heterogeneity.

    Results

    Of the included studies (n = 32), athletes experienced greater creatine kinase (CK) concentrations (Z = 4.99, p < 0.00001, I2 = 74%), inflammatory factors and other indirect measures of muscle damage in the initial phase of the preseason period compared to the off-season; there were no changes in CK (Z = 1.43, p = 0.15, I2 = 74%) across two time points of similar TL; and there were concurrent increases in CK with increases in TL (Z = 4.26, p < 0.0001, I2 = 36%) and vice versa (Z = 4.33, p < 0.0001, I2 = 79%).The qualitative analysis identified that the response of inflammatory factors and other indirect measures of muscle damage to changes in load were inconclusive.

    Limitations

    This review included varying age, sex, sports and competition levels. The group level meta-analysis failed to identify within-athlete or position-specific differences across time.

    Conclusion

    Blood biomarkers of EIMD may not differ across periods of similar TL, however can be considered a sensitive monitoring tool for assessing responses following acute TL changes in semi-elite and elite athletes.

  12. Abstract

    Background

    Netball is the one of the most popular women’s sports in the world. Since gaining professional status in 2008 there has been a rapid growth in research in the applied sports science and medicine of the sport. A scoping review of the area would provide practitioners and researchers with an overview of the current scientific literature to support on-court performance, player welfare and reduce injury.

    Objective

    The primary objective was to identify the current research on the applied sports science and medicine of netball. Additionally, the article provides a brief summary of the research in each topic of sports science and medicine in netball and identifies gaps in the current research.

    Methods

    Systematic searches of PubMed, SPORTDiscus, MEDLINE and CINAHL were undertaken from earliest record to Dec 2020 and reference lists were manually searched. The PRISMA-ScR protocol was followed. Studies were eligible for inclusion if they investigated netball as a sport or the applied sport science and medicine of netball athletes.

    Results

    962 studies were identified in the initial search, 150 of which met the inclusion criteria. Injury was the most highly investigated sport science and medicine topic (n = 45), followed by physical qualities (n = 37), match characteristics (n = 24), biomechanics (n = 15), psychology (n = 13), fatigue and recovery (n = 9), training load (n = 4) and nutrition (n = 3). A range of cohorts were used from school to elite and international standards. All cohorts were female netballers, except for one study. A rapid growth in studies over recent years was demonstrated with 65% of studies published in the last decade. There still remains gaps in the literature, with a low evidence base for nutrition, training load and fatigue and recovery.

    Conclusion

    This scoping review summarises the current evidence base and key findings that can be used in practice to enhance the applied sport science and medical support to netball athletes across a range of playing standards, and support the growth of the sport. It is evident that netball as a sport is still under-researched.

  13. Abstract

    Background

    Anterior cruciate ligament (ACL) injury is known to have a number of deleterious effects on lower limb muscle function. Alterations in muscle size are one such effect that have implications towards reductions in strength and functioning of the lower limbs. However, a comprehensive analysis of alterations in muscle size has yet to be undertaken.

    Objective

    To systematically review the evidence investigating lower limb muscle size in ACL injured limbs.

    Design

    Systematic review

    Data Sources

    Database searches of Medline, SPORTDiscus, Embase, Cinahl and Web of Science as well as citation tracking and manual reference list searching.

    Eligibility Criteria for Selecting Studies

    Individuals with ACL deficient or reconstructed limbs with an assessment of lower limb muscle size and control limb data (contralateral or uninjured control group)

    Methods

    Risk of bias assessment was completed on included studies. Data were extracted and where possible meta-analyses performed. Best evidence synthesis was also undertaken.

    Results

    49 articles were included in this review, with 37 articles included in the meta-analyses. 66 separate meta-analyses were performed using various measures of lower limb muscle size. Across all measures, ACL deficient limbs showed lesser quadriceps femoris muscle size (d range = − 0.35 to − 0.40), whereas ACL reconstructed limbs showed lesser muscle size in the quadriceps femoris (d range = − 0.41 to − 0.69), vastus medialis (d = − 0.25), vastus lateralis (d = − 0.31), hamstrings (d = − 0.28), semitendinosus (d range = − 1.02 to − 1.14) and gracilis (d range = − 0.78 to − 0.99) when compared to uninjured limbs.

    Conclusion

    This review highlights the effect ACL injury has on lower limb muscle size. Regardless of whether an individual chooses a conservative or surgical approach, the quadriceps of the injured limb appear to have lesser muscle size compared to an uninjured limb. When undertaking reconstructive surgery with a semitendinosus/gracilis tendon graft, the harvested muscle shows lesser muscle size compared to the uninjured limb.