Strength training as superior, dose-dependent and safe prevention of acute and overuse sports injuries: a systematic review, qualitative analysis and meta-analysis.

OBJECTIVE: This review aims to analyse strength training-based sports injury prevention randomised controlled trials (RCT) and present best evidence recommendations for athletes and future research. A priori PROSPERO registration; CRD42015006970. DESIGN: Systematic review, qualitative analysis and meta-analysis. Sorting of studies and quality assessments were performed by two independent authors. Qualitative analyses, relative risk (RR) estimate with robustness and strength of evidence tests, formal tests of publication bias and post-hoc meta-regression were performed. DATA SOURCES: PubMed, Embase, Web of Science and SPORTDiscus were searched to July 2017. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: RCTs on strength training exercises as primary prevention of sports injuries. RESULTS: Six studies analysed five different interventions with four distinct outcomes. 7738 participants aged 12-40 years were included and sustained 177 acute or overuse injuries. Studies were published in 2003-2016, five from Europe and one from Africa. Cluster-adjusted intention-to-treat analysis established RR 0.338 (0.238-0.480). The result was consistent across robustness tests and strength of evidence was high. A 10% increase in strength training volume reduced the risk of injury by more than four percentage points. Formal tests found no publication bias. CONCLUSION: The included studies were generally well designed and executed, had high compliance rates, were safe, and attained consistently favourable results across four different acute and overuse injury outcomes despite considerable differences in populations and interventions. Increasing strength training volume and intensity were associated with sports injury risk reduction. Three characteristically different approaches to prevention mechanisms were identified and incorporated into contemporary strength training recommendations.

Effect of Losartan on the Acute Response of Human Elderly Skeletal Muscle to Exercise.

PURPOSE: To investigate the effect of blocking the angiotensin II Type I receptor (AT1R) upon the response to acute heavy-resistance exercise in elderly human skeletal muscle. The hypothesis was that AT1R blocking would result in a superior myogenic response accompanied by down-regulation of transforming growth factor-beta and up-regulation of insulin-like growth factor-1 signaling. METHODS: Twenty-eight healthy elderly men (+64 yr) were randomized into two groups, consuming either AT1R blocker (losartan, 100 mg·d) or placebo for 18 d before exercise. Participants performed one bout of heavy-unilateral-resistance exercise. Six muscle biopsies were obtained from the vastus lateralis muscles of each subject: two before exercise and four after exercise (4.5 h and 1, 4, and 7 d). Blood pressure and blood samples were collected at the same time points. Biopsies were sectioned for immunohistochemistry to determine the number of satellite cells associated with Type I and Type II fibers. Gene expression levels of Notch, connective tissue, and myogenic signaling pathways were determined by real-time reverse transcription polymerase chain reaction. RESULTS: Changes over time were detected for circulating creatine kinase, the number of satellite cells per Type I fiber, and most of the gene targets, with no specific effect of losartan on these. However, when compared with placebo, losartan intake resulted in a greater suppression of myostatin messenger RNA. CONCLUSIONS: In general, there does not seem to be any effect of AT1R blocking on satellite cell number or myogenic pathways in elderly men in the days after one bout of heavy-resistance exercise. However, the greater suppression of myostatin may prove to be beneficial over a long-term intervention designed to induce hypertrophy.

A new approach to define and diagnose cardiometabolic disorder in children.

The aim of the study was to test the performance of a new definition of metabolic syndrome (MetS), which better describes metabolic dysfunction in children. Methods. 15,794 youths aged 6-18 years participated. Mean z-score for CVD risk factors was calculated. Sensitivity analyses were performed to evaluate which parameters best described the metabolic dysfunction by analysing the score against independent variables not included in the score. Results. More youth had clustering of CVD risk factors (>6.2%) compared to the number selected by existing MetS definitions (International Diabetes Federation (IDF) < 1%). Waist circumference and BMI were interchangeable, but using insulin resistance homeostasis model assessment (HOMA) instead of fasting glucose increased the score. The continuous MetS score was increased when cardiorespiratory fitness (CRF) and leptin were included. A mean z-score of 0.40-0.85 indicated borderline and above 0.85 indicated clustering of risk factors. A noninvasive risk score based on adiposity and CRF showed sensitivity and specificity of 0.85 and an area under the curve of 0.92 against IDF definition of MetS. Conclusions. Diagnosis for MetS in youth can be improved by using continuous variables for risk factors and by including CRF and leptin.

The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials.

BACKGROUND: Physical activity is important in both prevention and treatment of many common diseases, but sports injuries can pose serious problems. OBJECTIVE: To determine whether physical activity exercises can reduce sports injuries and perform stratified analyses of strength training, stretching, proprioception and combinations of these, and provide separate acute and overuse injury estimates. MATERIAL AND METHODS: PubMed, EMBASE, Web of Science and SPORTDiscus were searched and yielded 3462 results. Two independent authors selected relevant randomised, controlled trials and quality assessments were conducted by all authors of this paper using the Cochrane collaboration domain-based quality assessment tool. Twelve studies that neglected to account for clustering effects were adjusted. Quantitative analyses were performed in STATA V.12 and sensitivity analysed by intention-to-treat. Heterogeneity (I(2)) and publication bias (Harbord's small-study effects) were formally tested. RESULTS: 25 trials, including 26 610 participants with 3464 injuries, were analysed. The overall effect estimate on injury prevention was heterogeneous. Stratified exposure analyses proved no beneficial effect for stretching (RR 0.963 (0.846-1.095)), whereas studies with multiple exposures (RR 0.655 (0.520-0.826)), proprioception training (RR 0.550 (0.347-0.869)), and strength training (RR 0.315 (0.207-0.480)) showed a tendency towards increasing effect. Both acute injuries (RR 0.647 (0.502-0.836)) and overuse injuries (RR 0.527 (0.373-0.746)) could be reduced by physical activity programmes. Intention-to-treat sensitivity analyses consistently revealed even more robust effect estimates. CONCLUSIONS: Despite a few outlying studies, consistently favourable estimates were obtained for all injury prevention measures except for stretching. Strength training reduced sports injuries to less than 1/3 and overuse injuries could be almost halved.