Revisiting the stretch-induced force deficit:A systematic review with multilevel meta-analysis of acute effects

Background:When recommending avoidance of static stretching prior to athletic performance,authors and practitioners commonly refer to available systematic reviews.However,effect sizes(ES)in previous reviews were extracted in major part from studies lacking control conditions and/or prepost testing designs.Also,currently available reviews conducted calculations without accounting for multiple study outcomes,with ES:0.03 to 0.10,which would commonly be classified as trivial.Methods:Since new meta-analytical software and controlled research articles have appeared since 2013,we revisited the available literatures and performed a multilevel meta-analysis using robust variance estimation of controlled prepost trials to provide updated evidence.Furthermore,previous research described reduced electromyography activity—also attributable to fatiguing training routines—as being responsible for decreased subsequent performance.The second part of this study opposed stretching and alternative interventions sufficient to induce general fatigue to examine whether static stretching induces higher performance losses compared to other exercise routines.Results:Including 83 studies with more than 400 ES from 2012 participants,our results indicate a significant,small ES for a static stretch-induced maximal strength loss(ES=0.21,p=0.003),with high magnitude ES(ES=0.84,p=0.004)for stretching durations≥60 s per bout when compared to passive controls.When opposed to active controls,the maximal strength loss ranges between ES:0.17 to0.28,p<0.001 and 0.040 with mostly no to small heterogeneity.However,stretching did not negatively influence athletic performance in general(when compared to both passive and active controls);in fact,a positive effect on subsequent jumping performance(ES=0.15,p=0.006)was found in adults.Conclusion:Regarding strength testing of isolated muscles(e.g.,leg extensions or calf raises),our results confirm previous findings.Nevertheless,since no(or even positive)effects could be found for athletic performance,our results do not support previous recommendations to exclude static stretching from warm-up routines prior to,for example,jumping or sprinting.

Oxidative Stress in Collegiate Cross Country Skiers in Mid- and Post-Seasons

Purpose: The oxidative stress (OS) hypothesis of overtraining syndrome argues that increased production of free radicals through exercise cause muscle fatigue and damage resulting in lower athletic performance. Several studies have investigated OS immediately before and after exercise bouts in a training macrocycle. Our study aimed to compare OS of endurance athletes between a competition macrocycle and the immediate post-season recovery macrocycle. In addition, we aimed to identify athletes who experienced an unexplainable drop in athletic performance during the competition season in order to compare their OS to those who experienced no drop in performance. Methods: Fifteen members of the University of Alaska Fairbanks cross country ski team volunteered for this study. Blood samples were taken in early February (“mid-season”) and late April (“post-season”). Participants completed questionnaires regarding physical activity and athletic performance at the time of the blood draws. Plasma was analyzed for 4-hydroxynonenal (HNE), nitrotyrosine, nitric oxide (NOX), and superoxide dismutase (SOD). Significance was determined by Wilcoxon and Mann-Whitney tests. Results: Participants displayed significantly higher (p Conclusion: Signs of oxidative stress and mitigation during the post-season recovery macrocycle were higher in athletes who reported experiencing a drop in athletic performance during the competition season macrocycle.

Examining the Interrelationships between Motivation, Conscientiousness, and Individual Endurance Sport Performance

Personality traits and motivation have been predictive of athletic success. Conscientiousness, intrinsic motivation （IM）, and extrinsic motivation （EM） positively predict sport performance, while amotivation （AM） has a negative impact. This study examined the effects of both sport motivation and conscientiousness on athletic performance. Methods included a cross-sectional survey study of endurance athletes （N= 73）; including runners （56.1%）, swimmers （19.2%）, triathletes （6.8%）, rowers （2.7%）, and multi-sport athletes （15.1%）. Conscientiousness and motivation were assessed using questionnaires. Subjective ratings and objective scores of a recent performance（s） were collected. Regression analyses demonstrated that conscientiousness positively predicted IM and negatively predicted AM. AM negatively predicted subjective performance. IM and EM were not significant predictors of subjective performance. No variable significantly predicted objective performance. Results support the deleterious role of AM in performance. Compared to IM and EM, AM might be a more relevant construct when predicting performance in a sample of athletes with varying degrees of commitment. This construct may be of particular interest to clinicians due to its association with athletic burnout. Conscientiousness may serve as a protective factor against burnout.

Association between ACTN3 R577X genotype and risk of non-contact injury in trained athletes:A systematic review

Purpose:The aim of this study was to review,systematically,evidence concerning the link between the ACTN3 R577X polymorphism and the rates and severity of non-contact injuries and exercise-induced muscle damage in athletes and individuals enrolled in exercise training programs.Methods:A computerized literature search was performed in the electronic databases PubMed,Web of Science,and SPORTDiscus,from inception until November 2020.All included studies compared the epidemiological characteristics of non-contact injury between the different genotypes of the ACTN3 R577X polymorphism.Results:Our search identified 492 records.After the screening of titles,abstracts,and full texts,13 studies examining the association between the ACTN3 genotypes and the rate and severity of non-contact injury were included in the analysis.These studies were performed in 6 different countries(Spain,Japan,Brazil,China,the Republic of Korea,and Italy)and involved a total participant pool of 1093 participants.Of the studies,2 studies involved only women,5 studies involved only men,and 6 studies involved both men and women.All the studies included were classified as highquality studies(≥6 points in the Physiotherapy Evidence Database(PEDro)scale score).Overall,evidence suggests there is an association between the ACTN3 R577X genotype and non-contact injury in 12 investigations.Six studies observed a significant association between A CTN3 R577X polymorphism and exercise induced muscle damage:2 with non-contact ankle injury,3 with non-contact muscle injury,and 1 with overall non-contact injury.Conclusion:The present findings support the premise that possessing the ACTN3 XX genotype may predispose athletes to a higher probability of some non-contact injuries,such as muscle injury,ankle sprains,and higher levels of exercise-induced muscle damage.

Does orthotics use improve comfort,speed,and injury rate during running?A randomised control trial

BACKGROUND Running is a hugely popular sport.Unfortunately,running-related injury(RRI)rates are high,particularly amongst amateur and recreational runners.Finding ways to reduce RRI rates and maximise comfort and performance for runners is important.Evidence regarding whether orthotics can successfully improve these parameters is limited and contradicting.Further research is required to provide runners with clearer guidance on the usefulness of orthotics.AIM To investigate the effect of Aetrex Orthotics on comfort,speed and RRI rates during recreational running.METHODS One hundred and six recreational runners were recruited on a voluntary basis via running clubs and social media pages and randomised into either the intervention or control group.Participants in the intervention group ran with Aetrex L700 Speed Orthotics inserted in their usual running shoes,whilst participants in the control group ran in their usual running shoes with no orthotics.The study ran for an 8-wk period.Participants provided data relating to running comfort,distance,and time during weeks 3-6.Participants provided data relating to any RRIs they sustained during all 8 wks.Running distance and time were used to calculate running speed in miles per hour(mph).For each outcome variable,95%confidence intervals and P values were calculated to assess the statistical significance between the groups.For comfort and speed data,univariate multi-level analysis was performed,and for outcome variables with significant between group differences,multi-level multivariate analysis was performed to evaluate any confounding effects of gender and age.RESULTS Ninety-four participants were included in the final analysis(drop-out rate=11%).Comfort and speed from 940 runs and 978 injury data reports were analysed.Participants who ran with orthotics reported,on average,speeds 0.30 mph faster(P=0.20)and comfort scores 1.27 points higher(P≤0.001)than participants who ran with no orthotics.They were also 2.22 times less likely to sustain an injury(P=0.08)than participants who ran with no orthotics.However,findings were only significant for comfort and not for speed or injury rates.Age and gender were found to be significant predictors of comfort.However,the improvements in comfort reported by participants who ran with orthotics were still significant after adjusting for age and gender.CONCLUSION This study found orthotics to improve comfort and speed and prevent RRIs whilst running.However,these findings were only statistically significant for comfort.

Does orthotics use improve comfort,speed and injury rate during running?Preliminary analysis of a randomised control trial

BACKGROUND Evidence regarding the effectiveness of using orthotics in improving comfort,increasing running speed and helping to reduce injury rate during running is limited and mixed.Alongside the increasing popularity of running is the increasing rate of running-related injuries(RRIs).Further research into whether orthotics could be used to help reduce RRIs would be highly beneficial for those affected.Additionally,there is a need to clarify whether orthotics use increases comfort during running and helps improve running speed.AIM To investigate whether running with Aetrex Orthotics improves comfort and performance and reduces injury whilst running.METHODS Runners were recruited on a voluntary basis if they were 18 or older with no serious health conditions,ongoing foot pain or deformity,previous foot surgery in their lifetime or any surgery in the past 6 mo.Participants were randomly assigned to either an intervention group or a control group.All participants were asked to complete runs and provide quantitative data regarding comfort during running,running time and distance,and any RRIs over an 8-wk study period.Participants in the intervention group ran with Aetrex L700 Speed Orthotics,whilst participants in the control group ran without orthotics.Other than the addition of orthotics for participants in the intervention group,all participants were asked to run as they usually would.This report presents preliminary data from the first 47 participants recruited for this study.Running speed was calculated from running distance and time and given in miles per hour.For each outcome variable,the mean for each group,effect size and 95%confidence interval were calculated,and a t-test was performed to determine if between-group differences were statistically significant.RESULTS Data for all three primary outcomes was provided from a total of 254 runs by the 23 participants in the intervention group and a total of 289 runs by the 24 participants in the control group.Participants in the intervention group reported higher comfort scores(8.00±1.41 vs 6.96±2.03,P≤0.0001),faster running speeds(6.27±1.03 vs 6.00±1.54,P=0.013),and lower RRI rates(0.70±1.01 vs 1.21±1.53,P=0.18)than those in the control group.These findings were statistically significant for comfort and running speed but not for RRI rate,with statistical significance considered if P<0.05.No adjustments were made for group differences in age,gender,tendency for RRIs or usual running speed.CONCLUSION This preliminary report provides evidence for orthotics use in increasing comfort levels and running speed,but no significant difference in RRI rate.

Swimrun race,athletes,safety and performance:A brief review

Swimrun was established in Sweden in 2006.In competition athletes alternate between running and swimming multiple times.It has grown from only being hosted in Sweden to now being a global sport.The swimrun race exposes athletes to environments that require a unique set of skills.For example,participants have to negotiate ocean currents and waves.The environmental conditions change between the runs and the swims.Athletes may be exposed to hot temperatures when running in wetsuits(25℃and hotter)and cold water(colder than 16℃)when swimming.This sudden change in environmental conditions imposes a poorly defined physiological stress on the participants.Research on the demands of swimrun is scarce.More research is needed to improve athlete safety during events.Also,research is needed to provide insight into enhancing training methods and performance.