Physical inactivity is the fourth leading cause of mortality worldwide;regardless of geographic location and income,it is a contributing risk factor to the other three causes.Physical activity is really a drug,a poly-...Physical inactivity is the fourth leading cause of mortality worldwide;regardless of geographic location and income,it is a contributing risk factor to the other three causes.Physical activity is really a drug,a poly-pill;its“regular use”can reduce this risk throughout the activation of a plethora of responses in virtually all the body tissues.The beneficial effects of physi-cal activity on cardiovascular function and hemodynamics are mainly mediated by skeletal muscle,adipose tissue and the immune system via the usage,delivery and distribution of metabolic substrates and improvement in inflammatory status.There is emerging evidence for exercise-dependent changes in bone metabolism as well;with improved bone quality,reduced fracture risk and increased bone endocrine function,the last of which modulates energy metabolism through its effects on pancreatic islet cells,skeletal muscle and adipose tissue.Bone endocrine function relies on the integration of biomechani-cal stimuli and endocrine signals from other organs and tissues.Here I review current concepts about exercise-dependent modulation of bone endocrine function and its beneficial effects on whole-body metabolism.Several molecular mechanisms have been identified that support this exercise-stimulated bone-mediated metabolic effect and,among these,Wnt signaling,fibroblast growth factor-23,bone morphogenic protein-7,osteocalcin,RANK/RANKL/OPG axis,and lipocalin-2 gave the largest evidences.In conclusion,beside the controversies surrounding technical aspects of the exercise,the efficacy of physi-cal activity in preventing/treating metabolic and inflammatory dysfunctions also passes throughout the bone.展开更多
At the 2022 Winter Olympics in Beijing,the XC skiing,biathlon and nordic combined events will be held at altitudes of~1700 m above sea level,possibly in cold environmental conditions and while requiring adjustment to ...At the 2022 Winter Olympics in Beijing,the XC skiing,biathlon and nordic combined events will be held at altitudes of~1700 m above sea level,possibly in cold environmental conditions and while requiring adjustment to several time zones.However,the ongoing COVID-19 pandemic may lead to sub-optimal preparations.The current commentary provides the following evidence-based recommendations for the Olympic preparations:make sure to have extensive experience of training(>60 days annually)and competition at or above the altitude of competition(~1700 m),to optimize and individualize your strategies for acclimatization and competition.In preparing for the Olympics,10-14 days at~1700 m seems to optimize performance at this altitude effectively.An alternative strategy involves two-three weeks of training at>2000 m,followed by 7-10 days of tapering off at~1700 m.During each of the last 3 or 4 days prior to departure,shift your sleeping and eating schedule by 0.5-1 h towards the time zone in Beijing.In addition,we recommend that you arrive in Beijing one day earlier for each hour change in time zone,followed by appropriate timing of exposure to daylight,meals,social contacts,and naps,in combination with a gradual increase in training load.Optimize your own individual procedures for warming-up,as well as for maintaining body temperature during the period between the warm-up and competition,effective treatment of asthma(if necessary)and pacing at~1700 m with cold ambient temperatures.Although we hope that these recommendations will be helpful in preparing for the Beijing Olympics in 2022,there is a clear need for more solid evidence gained through new sophisticated experiments and observational studies.展开更多
The present review deals with the current scientific knowledge related with ski jump landing.A specific focus is given on the landing biomechanics,the methods utilized for its analysis and the injuries connected to th...The present review deals with the current scientific knowledge related with ski jump landing.A specific focus is given on the landing biomechanics,the methods utilized for its analysis and the injuries connected to the landing phase.Despite the demonstrated importance for the safety and the performance of ski jumpers,the landing and its preparation are rarely inves-tigated.In this paper,after having firstly described the execution of landing and its preparation and the reason why is impor-tant to analyze it,an overview of the current status of the research related to the landing biomechanics is reported(kinetics,kinematics,electromyographic activation,aerodynamics,computer simulation).The third part describes the methods and technologies utilized in literature to analyze the landing and its preparation(video cameras,inertial sensors,force insoles,wind tunnel and computer simulation).After that,an overview of the injuries related to landing is reported.The final section proposes future research in the field of biomechanics of ski jump landing in different fields,such as computer simulations,kinematic analysis,equipment development and biomechanics of female athletes.展开更多
Purpose The aim of this study was to investigate whether skeletal muscle-derived follistatin-like 1(FSTL1)reaches the heart and exerts the angiogenetic function in rats suffering myocardial infarctions(MI)after exerci...Purpose The aim of this study was to investigate whether skeletal muscle-derived follistatin-like 1(FSTL1)reaches the heart and exerts the angiogenetic function in rats suffering myocardial infarctions(MI)after exercise intervention.Methods Forty-eight male adult Sprague-Dawley rats were randomly divided into four groups.MI was provoked by ligation of left anterior descending coronary artery.MI rats underwent adeno-associated virus injection of FST1 in tibialis anterior muscle and 4 weeks of resistance exercise via a tail-suspended incremental weight-climbing method(0-75%body weight,daily load increased by 10%;1 h/day,5 day/w).Heart function was evaluated by hemodynamics including LVSP,LVEDP and±dP/dt max;the cross-sectional area of muscle cells and myocardium fibrosis were analyzed by DiI and Masson’s stain-ing,respectively;the FSTL1 expression,endothelial cell proliferation and angiogenesis were visualized by immunofluores-cence staining;and protein expression was quantified by Western blotting.Results Resistance exercise reverted MI-induced skeletal muscle atrophy,increased muscle FSTL1 expression and stimulated skeletal muscle derived FSTL1 entering into the MI heart via blood circulation.The overexpression of skeletal muscle FSTL1 improved myocardial endothelial cell proliferation,increased small vessel density in the fibrotic border,inhibited myocardial fibrosis and improved heart function in the MI rats after the exercise intervention.Meanwhile,DIP2A-PI3K-Akt-mTOR,Erk1/2 and TGFβ-Smad2/3 pathways were activated in the myocardium.Conclusion Resistance exercise stimulates skeletal muscle derived FSTL1 to reach the myocardium which makes a positive contribution to cardioprotection in MI rat.展开更多
This study aimed to determine the net energy expenditure(EENET)required for overground walking and running 1200 m in a sample of healthy adolescent boys and girls.A secondary purpose was to describe the effect of body...This study aimed to determine the net energy expenditure(EENET)required for overground walking and running 1200 m in a sample of healthy adolescent boys and girls.A secondary purpose was to describe the effect of body composition on energy expenditure(EE)of walking versus running.Twenty healthy adolescents(9 boys,11 girls)aged 15.85±2.80 years performed 2 field tests in regular outdoor conditions:overground walking(1.64±0.17 m/s)and submaximal running(3.13±0.42 m/s),at a self-selected steady pace.EE was measured via indirect calorimetry.Paired sample t-tests were used to determine if there were differences between walking and running conditions and mean percentage differences were estimated for various physiological parameters.Differences in EENET between conditions were performed for both genders using a two(condition)by two(gender)analysis of variance repeated measures design,with fat free mass as a covariate.Speed increased by 90.43%between the 2 conditions,while the different components of EE increased by almost 20%.Running elicited a significantly greater EENET than walking for both genders;however,boys’and girls’EE did not differ significantly.When EENET was adjusted for fat free mass,there was a statistically significant condition×fat free mass effect.The findings in this study indicate that both adolescent boys and girls expend more energy during running than walking,without being affected by body composition.Body mass and fat free mass significantly correlated with EE only during running.In addition,the trained participants of the study optimized locomotion to minimize EE.展开更多
Purpose The purpose of the study was to investigate the acute effect of a beginner martial art class and aerobic exercise on executive function(EF)in college-aged young adults.There is overwhelming evidence that demon...Purpose The purpose of the study was to investigate the acute effect of a beginner martial art class and aerobic exercise on executive function(EF)in college-aged young adults.There is overwhelming evidence that demonstrates acute as well as long-term aerobic exercise improves EF.Nevertheless,there is limited research comparing externally paced exercise(EPE)to self-paced exercise(SPE)such as walking on improving EF.EPE requires greater cortical demand than SPE to execute a motor plan.Methods Eight men and eight women,aged 24.2±2.8 years,participated in a Repeated Measures Crossover Design.Pre-and post-testing of EF with the Stroop and Tower of London(ToL)and stress level were measured after each of the two 1-h conditions:the SPE consisted of a walk(aerobic exercise)and the EPE was a beginner martial art class.Results There were significant main effects for the martial art class for the Stroop’s mean reaction time for congruent trials(P=0.01)with a large-effect size.The mean reaction time for incongruent trials was significant(P=0.05)with a medium-effect size.The ToL’s mean solution time(P=0.003)and mean execution time(P=0.002)were also significant with large-effect sizes.Stress levels were not significantly improved following either condition.Conclusion The martial art class significantly improved all the major domains of EF,while aerobic exercise of a similar intensity did not demonstrate any measured significant changes.The physiological benefits of physical exercise are well documented;however,the cognitive enhancing capability of EPE should also be appreciated given the results of this study.展开更多
Beijing will host the 2022 Winter Olympics,and China strengthens research on various aspects to allow their athletes to compete successfully in winter sport.Simultaneously,Government-directed initiatives aim to increa...Beijing will host the 2022 Winter Olympics,and China strengthens research on various aspects to allow their athletes to compete successfully in winter sport.Simultaneously,Government-directed initiatives aim to increase public participation in recreational winter sport.These parallel developments allow research to advance knowledge and understanding of the physiological determinants of performance and health related to winter sport.Winter sport athletes often conduct a substan-tial amount of training with high volumes of low-to-moderate exercise intensity and lower volumes of high-intensity work.Moreover,much of the training occur at low ambient temperatures and winter sport athletes have high risk of developing asthma or asthma-related conditions,such as exercise-induced bronchoconstriction.The high training volumes require optimal nutrition with increased energy and dietary protein requirement to stimulate muscle protein synthesis response in the post-exercise period.Whether higher protein intake is required in the cold should be investigated.Cross-country ski-ing is performed mostly in Northern hemisphere with a strong cultural heritage and sporting tradition.It is expected that innovative initiatives on recruitment and training during the next few years will target to enhance performance of Chinese athletes in classical endurance-based winter sport.The innovation potential coupled with resourcing and population may be substantial with the potential for China to become a significant winter sport nation.This paper discusses the physiological aspects of endurance training and performance in winter sport highlighting areas where innovation may advance in athletic performance in cold environments.In addition,to ensure sustainable development of snow sport,a quality ski patrol and rescue system is recommended for the safety of increasing mass participation.展开更多
Although reliable feedback is crucial to improving the performance of competitive alpine skiers,the coach’s eye may not be sensitive enough to detect small,but highly significant“mistakes”.Monitoring of the perform...Although reliable feedback is crucial to improving the performance of competitive alpine skiers,the coach’s eye may not be sensitive enough to detect small,but highly significant“mistakes”.Monitoring of the performance of alpine ski racers by inertial motion units(IMU)has proven to be of value in this context and here we summarize practical and methodological aspects of this approach.Methodologically,the IMUs employed should combine high sampling frequencies with minimal signal drift.The sensors should be positioned to sense the movement of the bones in a given body segment while being pro-tected as much as possible against impact with the ski gates.The data obtained,often synchronized with input from Global Satellite Navigation Systems(GNSS),are usually refined utilizing advanced biomechanical models and other computerized approaches.In practice,the combination of inertial sensors and GNSS allows accurate monitoring of skiing kinematics(technique)and the movement of the skier’s center-of-mass,also allowing analysis of both whole-body vibrations(WBV)and loss of mechanical energy.Presentation of the findings to coaches and athletes can be facilitated by synchronizing them with video recordings.Recent advances in IMU technology,including miniaturization,wireless communication,direct stor-age of data in the cloud,and processing with artificial intelligence may allow these sensors,in-combination with GNSS,to become real-time virtual alpine ski coaches,perhaps the next step in the development of this sport.展开更多
Purpose This study aimed to investigate the relationships between vertical jump metrics and phases during a 60 m sprint.The variances in strength qualities between sprinters of different ability levels were also compa...Purpose This study aimed to investigate the relationships between vertical jump metrics and phases during a 60 m sprint.The variances in strength qualities between sprinters of different ability levels were also compared.Methods Eighteen young male elite sprinters(age:18.1±1.3 years;stature:1.72±0.07 m;body mass:66.3±6.2 kg)were assessed for squat(SJ),countermovement(CMJ),drop(DJ),and standing long jumps,a maximal load back-squat,and a 60-m sprint from a block-start.The relationships between sprint performances with all variables were analysed using correlation and multiple regression while discriminative parameters between fast(100 m time:~10.50 s)and slow(~11.00 s)sprint groups were assessed using independent t-tests.Results Higher associations existed between vertical jumps and longer sprint distances,especially between SJ height and relative peak power with 10 m(r=−0.47 and−0.47,respectively),30 m(−0.71 and−0.74),60 m(−0.76 and−0.81),10-30 m(−0.80 and−0.86),and 30-60 m(−0.78 and−0.84)sprint distances.Concurrently,variables such as relative maximal-strength,relative SJ parameters(height,peak force,and peak power),relative CMJ peak power,and reactive strength index(DJ from 35 cm height)had significant discriminative ability and correlations(P<0.05)with sprint distances involving maximal velocity and flying-start.Additionally,a combination of SJ height and relative maximal-strength during back-squat accounted for 75%of the variance in 60 m sprint times.Conclusions Relative measures of multiple strength metrics may provide better insight regarding factors that enhance sprint performance.Adequate maximal-strength,high explosive power,and reactive strength seem necessary to improve sprint performance in young male elite sprinters.展开更多
Purpose Main purposes of pre-acclimatization by hypoxia conditioning(HC)are the prevention of high-altitude illnesses and maintenance of aerobic exercise performance.However,robust evidence for those effects or eviden...Purpose Main purposes of pre-acclimatization by hypoxia conditioning(HC)are the prevention of high-altitude illnesses and maintenance of aerobic exercise performance.However,robust evidence for those effects or evidence-based guidelines for exposure strategies,including recommendations to ensure safety,are largely lacking.Therefore,we summarize the current knowledge on the physiology of acclimatization to hypoxia and HC with the aim to derive implications for pre-acclimatization strategies before going on high-altitude treks and expeditions.Methods Based on the literature search and personal experience,core studies and important observations have been selected in order to present a balanced view on the current knowledge of high-altitude illnesses and the acclimatization process,specifically focusing on pre-acclimatization strategies by HC.Results and Conclusions It may be concluded that in certain cases even short periods(e.g.,7 h)of pre-acclimatization by HC are effective,but longer periods(e.g.,>60 h)are needed to elicit more robust effects.About 300 h of HC(intermittently applied)may be the optimal preparation for extreme altitude sojourns,although every additional hour spent in hypoxia may confer further benefits.The inclusion of hypobaric exposures(i.e.,real altitude)in pre-acclimatization protocols could further increase their efficacy.The level of simulated altitude is progressively increased or individually adjusted ideally.HC should not be terminated earlier than 1-2 weeks before altitude sojourn.Medical monitoring of the pre-acclimatization program is strongly recommended.展开更多
Purpose The purpose was to investigate whether an increased amount of training while carrying the rifle affects skiing in well-trained biathletes at submaximal and maximal workloads during a pre-season period lasting ...Purpose The purpose was to investigate whether an increased amount of training while carrying the rifle affects skiing in well-trained biathletes at submaximal and maximal workloads during a pre-season period lasting a minimum of 12 weeks.Methods Seventeen well-trained biathletes(9 females,8 males)were assigned to an intervention(IG,n=10)or control(CG,n=7)group.Before(T1)and after(T2)the training intervention all participants performed,using treadmill roller-skiing,a submaximal test without the rifle on one day and two submaximal workloads and a maximal time trial(TT)with the rifle on a subsequent day.Between T1 and T2 all participants performed a minimum of 12 weeks of normal training,the only difference between groups being that IG performed more of their training sessions carrying the rifle.Results IG performed more training compared to CG(15.4±1.1 vs.11.2±2.6 h/week,P<0.05),including a higher amount of training with the rifle(3.1±0.6 vs.1.1±0.3 h/week,P<0.001).Speed at 4 mmol/L of blood lactate increased significantly for CG from T1 to T2(P=0.028),while only tended to increase for IG(P=0.058).Performance during the TT,VO2max and the aerobic metabolic rate increased significantly from T1 to T2,although the differences disappeared when including the speed at baseline as a covariate.Conclusion According to the present results,increasing training while carrying the rifle by 2 h/week does not appear to improve skiing performance in well-trained biathletes.In addition,physiological markers at submaximal and maximal intensities while carrying the rifle were not affected after the training intervention.展开更多
Cross-country(XC)ski races involve a variety of formats,two different techniques and tracks with highly variable topography and environmental conditions.In addition,XC skiing is a major component of both Nordic combin...Cross-country(XC)ski races involve a variety of formats,two different techniques and tracks with highly variable topography and environmental conditions.In addition,XC skiing is a major component of both Nordic combined and biathlon competi-tions.Research in this area,both in the laboratory and field,encounters certain difficulties that may reduce the reliability and validity of the data obtained,as well as complicate comparisons between studies.Here,13 international experts propose specific guidelines designed to enhance the quality of research and publications on XC skiing,as well as on the biathlon and Nordic combined skiing.We consider biomechanical(kinematic,kinetic and neuromuscular)and physiological methodology(at the systemic and/or muscle level),providing recommendations for standardization/control of the experimental setup.We describe the types of measuring equipment and technology that are most suitable in this context.Moreover,we also deal with certain aspects of nomenclature of the classical and skating sub-techniques.In addition to enhancing the quality of stud-ies on XC skiing,Nordic combined and biathlon,our guidelines should also be of value for sport scientists and coaches in other disciplines where physiological and/or biomechanical measurements are performed in the laboratory and/or outdoors.展开更多
Purpose To challenge current conventions in paediatric sport science and use data from recent longitudinal studies to elu-cidate the development of aerobic and anaerobic fitness,with reference to youth athletes.Method...Purpose To challenge current conventions in paediatric sport science and use data from recent longitudinal studies to elu-cidate the development of aerobic and anaerobic fitness,with reference to youth athletes.Methods(1)To critically review the traditional practice of ratio scaling physiological variables with body mass and,(2)to use multiplicative allometric models of longitudinal data,founded on 1053(550 from boys)determinations of 10-17-year-olds’peak oxygen uptake(VO2)and 763(405 from boys)determinations of 11-17-year-olds’peak power output(PP)and mean power output(MP),to investigate the development of aerobic and anaerobic fitness in youth.Results The statistical assumptions underpinning ratio scaling of physiological variables in youth are seldom met.Multiplicative allometric modelling of longitudinal data has demonstrated that fat free mass(FFM)acting as a surrogate for active muscle mass,is the most powerful morphological influence on PP,MP,and peak VO2.With FFM appropriately controlled for,age effects remain significant but additional,independent effects of maturity status on anaerobic and aerobic fitness are negated.Conclusions Ratio scaling of physiological variables with body mass is fallacious,confounds interpretation of the develop-ment of anaerobic and aerobic fitness,and misleads fitness comparisons within and across youth sports.Rigorous evalua-tion of the development of anaerobic and aerobic fitness in youth requires longitudinal analyses of sex-specific,concurrent changes in age-and maturation-driven morphological covariates.Age and maturation-driven changes in FFM are essential considerations when evaluating the physiological development of youth athletes.展开更多
Purpose Cystic Fibrosis(CF)is a multisystem disease associated with symptoms such as dyspnoea,tachycardia and tachyp-nea that may be related to changes in autonomic function and sensitive to improvement following insp...Purpose Cystic Fibrosis(CF)is a multisystem disease associated with symptoms such as dyspnoea,tachycardia and tachyp-nea that may be related to changes in autonomic function and sensitive to improvement following inspiratory muscle training(IMT).The aim of the present study was to investigate the effect of IMT on heart rate variability(HRV)and respiratory function in children.Methods Five CF and five matched controls(40%boys)performed a 4-weeks IMT programme,involving 30 breaths,twice a day.Weeks 1-2 of training were set at 40%of a participant's maximal strength index(S.Index),with week's 3-4 set at 50%.Participants wore an ActiHeart for three consecutive days at baseline and post-intervention and indices of HRV were derived.Standard measures of lung function were obtained along with health-related quality of life(HRQoL)using the CF-specific questionnaire(CFQ-R).Results IMT elicited clinically meaningful increases in respiratory muscle strength and respiratory symptom domain scores,but no improvements in respiratory volume,irrespective of group.Similarly,no significant improvements were found in HRQoL despite 62.5%of the population increased their HRQoL score.Post-intervention,CF participants showed a clinically meaningful decrease in the very low frequency(VLF)domain.Conclusion These results may indicate clinically meaningful changes in HRV and inspiratory muscle strength following a 4-week IMT intervention,although a more powerful study is required to draw further conclusions.Indeed,the trends for improved HRQoL support the need for such studies to ascertain the potential therapeutic role of IMT in those with CF.展开更多
Purpose To quantify the effects of an externally worn collar device for mitigating the influence of repetitive head impacts on alterations to diffusion tensor imaging(DTI)metrics of white matter.Methods Fifteen female...Purpose To quantify the effects of an externally worn collar device for mitigating the influence of repetitive head impacts on alterations to diffusion tensor imaging(DTI)metrics of white matter.Methods Fifteen female high-school soccer athletes(age:14.00-16.98 yrs)completed pre-and post-season DTI over two consecutive years,including measures of diffusivity,changes in which may be associated with brain dysfunction.The collar was worn during year 1(Yr1)but not during year 2(Yr2).Athlete exposures(AEs)and head impact exposure were recorded over the competitive seasons.Results There were no significant differences in AEs or head impact exposures between Yr1 and Yr2(P>0.05).In Yr2,there was significant pre-to post-season mean diffusivity and/or axial diffusivity reduction in multiple WM regions(cor-rected P<0.05).Pre-to post-season mean diffusivity,axial diffusivity,and radial diffusivity decreases were 3.04%±2.53%,2.97%±2.19%,and 3.37%±3.34%,respectively,significantly greater than pre-to post-season changes in Yr1(mean dif-fusivity:-0.31%±1.78%,P=0.0014;axial diffusivity:-0.02%±2.25%,P=0.0014;radial diffusivity:-0.63%±2.10%,P=0.0030).Conclusions Mild bilateral compression to athletes'internal jugular vein through collar application may have increased intracranial blood volume and spatially redistributed head-impact-derived brain energy absorption.However,future research is needed to elucidate the potential clinical significance of WM changes of various degrees.Clinical trails registration NCT03014492.展开更多
Purpose To investigate the physiological responses to low-load,superset resistance training(two exercises for the agonist and antagonist muscles performed without rest between exercises)to failure using elastic bands....Purpose To investigate the physiological responses to low-load,superset resistance training(two exercises for the agonist and antagonist muscles performed without rest between exercises)to failure using elastic bands.Methods Twenty-three athletes were randomized to either a superset group(S,n=12,average age:19.8±1.5 years)or a traditional set group(T,n=11,average age:20.1±1.4 years).Strength,cross-sectional area(CSA)and muscular endurance of the biceps and triceps brachii were assessed before and after 8 weeks.Acute responses(muscle thickness)were measured during one testing session.Results Muscle thickness of the biceps significantly increased in both T group(P<0.05)and S group(P<0.05)after a single bout of Training.The triceps did not show significant increases in either T group(P>0.05)or S group(P>0.05).Blood lactate also increased in both groups after one bout of training(T:from 1.3±0.3 to 5.5±2.4 mmol/L,S:from 1.4±0.5 to 5.1±1.5 mmol/L,P<0.05).After 8-week training,both groups showed significant increases in the biceps(T:13.2%±5.0%;S:12.9%±7.3%,P<0.05)and triceps(T:9.5%±9.3%,S:4.8%±4.1%,P<0.05)without differences between groups.Increases in one repetition maximum for the bench press(7.8%±6.5%,P<0.05)and maximal voluntary contraction for the arm extensors(9.3%±11.6%,P<0.05)were observed for the T group only.Increases in muscular endurance were observed only in the S group for the bench press(26.0%±19.1%,P<0.05)and the barbell curl(17.2%±16.6%,P<0.05).Conclusions Superset training may enhance muscular endurance while attenuating maximal strength gains.There does not appear to be a hypertrophic benefit to performing superset training,but it may provide a time-efficient strategy to achieve adaptations in muscle mass.展开更多
Purpose To evaluate the effects of acute moderate-intensity exercise on ecological memory,as assessed from a face-name memory task.Methods A two-arm,parallel-group,randomized controlled intervention was employed.Parti...Purpose To evaluate the effects of acute moderate-intensity exercise on ecological memory,as assessed from a face-name memory task.Methods A two-arm,parallel-group,randomized controlled intervention was employed.Participants(N=40;Mage=20.8 years)were randomized into a seated control task or a bout of acute moderate-intensity treadmill exercise(15-min).Thereafter,participants completed a 3-phase face-name memory task,involving a study phase and two test phases(immediate and delayed recall,with the delay occurring 15 min after the immediate recall).Results For the immediate memory recall,the mean(SD)scores for the exercise and control conditions,respectively,were 6.60(2.5)and 6.20(2.5).For the 15-min delayed assessment,the respective scores were 6.25(2.6)and 5.75(1.9).There was a significant main effect for time(F=4.06,P=0.05, η^(2)_(p)=0.10).However,there were no main effects for group(F=0.33,P=0.56, η^(2)_(p)=0.01)or time by group interactions(F=0.12,P=0.72, η^(2)_(p)=0.003).Conclusions Despite the exercise group having slightly higher immediate and delayed face-name memory scores,we did not observe robust evidence of acute exercise enhancing face-name memory performance.展开更多
Purpose To analyze the inter-limb coordination patterns and energy recovery of elite cross-country skiers performing double poling(DP).Methods Thirty-three elite athletes in three track sections of FIS-WC races,with d...Purpose To analyze the inter-limb coordination patterns and energy recovery of elite cross-country skiers performing double poling(DP).Methods Thirty-three elite athletes in three track sections of FIS-WC races,with different slopes(2°,0°and−1.5°).Stereo vision capture system(50 Hz cameras)and 3D analysis were used to extract:kinematic parameters(center of gravity,veloc-ity);joint angles and angular velocities;energy(potential and kinetic)and energy recovery indices R% and R(t)during the entire DP cycle and within poling(R_(pol))and swing phase(R_(swi)).Results Average race velocity of the centre of gravity(V_(ave))significantly varied according to slopes(5.4,7.3 and 8.3 m/s).This correlated with differences in the angular velocities of the most relevant joints.Elbow flexion angular velocity in the early portion of poling phase was higher according to the slope variations(−137,−171 and−202 deg/s,for the slopes 2°,0°and−1.5°,respectively),indicating the possible modulation of muscular stretch shortening cycle(SSC).A similar trend was observed for shoulder angular velocity which increased during poling phase,and for knee extension velocity during swing phase,and for knee extension velocity during swing phase.R%decreased significantly for the−1.5°slope(32%and 24%vs.15%);R(t)was higher for the Rswi.Significant differences were observed in trunk-elbow,trunk-shoulder,trunk-knee and elbow-shoulder patterns for the−1.5°slope with respect to the others.Conclusions Despite the modest variation of the track’s slope,the effects on propulsion and recovery strategies were different.展开更多
Purpose To investigate the effects of 4 weeks high-intensity interval training in hypoxia on aerobic and anaerobic perfor-mance of 3-on-3 basketball players.Methods In a randomised controlled trial,15 female basketbal...Purpose To investigate the effects of 4 weeks high-intensity interval training in hypoxia on aerobic and anaerobic perfor-mance of 3-on-3 basketball players.Methods In a randomised controlled trial,15 female basketballers completed eight 1-h high-intensity training sessions in either normobaric hypoxia(hypoxic group n=8,altitude 3052 m)or normoxia(normoxic group n=7,sea-level).Results After training,the hypoxic group increased their 1-min all-out shuttle run distance by 2.5%±2.3%(mean±95%CI,d=0.83,P=0.04),compared to the normoxic group 0.2%±2.3%(d=0.06,P=0.8),with the difference between groups being clinically worthwhile but not statistically significant(d=0.77,P=0.1).Distance covered in the Yo-Yo intermittent recovery test tended to increase in the hypoxic(32.5%±39.3%,d=1.0,P=0.1)but not normoxic group(0.3%±24.5%,d=0.08,P=0.9),with a non-significant change between groups(d=0.9,P=0.2).Compared to normoxia,the hypoxic group significantly increased subjective markers of stress(d=0.53,P=0.005),fatigue(d=0.43,P=0.005),and muscle soreness(d=0.46,P=0.01),which resulted in a lower perceived training performance in the hypoxic compared to the normoxic group(d=0.68,P=0.001).Conclusion High-intensity interval training under hypoxic conditions likely improved 1-min all-out shuttle run ability in female basketball 3-on-3 players but also increased subjective markers of stress and fatigue which must be taken into con-sideration when prescribing such training.展开更多
Purpose Isometric strength training (IST) with rapid non-sustained contraction (RIST) is effective in improving the ability to generate force rapidly.However,the neuromuscular adaptation of IST with sustained contract...Purpose Isometric strength training (IST) with rapid non-sustained contraction (RIST) is effective in improving the ability to generate force rapidly.However,the neuromuscular adaptation of IST with sustained contraction (SIST) and RIST is not known.Therefore,the aim of the study was to compare the neuromuscular adaptations of RIST with SIST.Methods Thirty-three national floorball players (23.9 ± 3.1 years old;1.69± 0.08 m;64.6± 11.1 kg) were recruited for this study.Pre-and post-test included countermovement jump (CMJ),30-m sprint (TT30),isometric squat at 90° (ISqT90) and 120° (ISqT120) knee angles.They were randomly assigned to either control (Con) (n =9),RIST (n =12) or SIST (n =12)group and performed 12 sessions of intervention training.All groups performed the same sets of exercises,but RIST and SIST had to perform ISqT with and without sustained contraction,respectively.Results Time × group effect for CMJ height (P =0.01,η2p=0.25),peak force (PF) (P =0.03,η2p =0.22) and rate of force development (RFD) (P =0.02,η2p =0.22) obtained from ISqT 120 were noted.A main effect for time was observed in CMJ height,PF obtained from ISqT90 and ISqT120,and RFD obtained from ISqT90 (P < 0.01,0.27 < η2p < 0.57).There was greater improvement in TT30 (P =0.043,d =3.00),ISqT90 PF (P =0.034,d =3.12),ISqT 120 PF (P =0.003,d =4.54) and ISqT120 RFD (P=0.033,d=1.36) in the SIST than the Con group.Conclusion SIST was more effective in improving strength and dynamic performance as compared to RIST,making it a viable training method to enhance dynamic performances.展开更多
文摘Physical inactivity is the fourth leading cause of mortality worldwide;regardless of geographic location and income,it is a contributing risk factor to the other three causes.Physical activity is really a drug,a poly-pill;its“regular use”can reduce this risk throughout the activation of a plethora of responses in virtually all the body tissues.The beneficial effects of physi-cal activity on cardiovascular function and hemodynamics are mainly mediated by skeletal muscle,adipose tissue and the immune system via the usage,delivery and distribution of metabolic substrates and improvement in inflammatory status.There is emerging evidence for exercise-dependent changes in bone metabolism as well;with improved bone quality,reduced fracture risk and increased bone endocrine function,the last of which modulates energy metabolism through its effects on pancreatic islet cells,skeletal muscle and adipose tissue.Bone endocrine function relies on the integration of biomechani-cal stimuli and endocrine signals from other organs and tissues.Here I review current concepts about exercise-dependent modulation of bone endocrine function and its beneficial effects on whole-body metabolism.Several molecular mechanisms have been identified that support this exercise-stimulated bone-mediated metabolic effect and,among these,Wnt signaling,fibroblast growth factor-23,bone morphogenic protein-7,osteocalcin,RANK/RANKL/OPG axis,and lipocalin-2 gave the largest evidences.In conclusion,beside the controversies surrounding technical aspects of the exercise,the efficacy of physi-cal activity in preventing/treating metabolic and inflammatory dysfunctions also passes throughout the bone.
文摘At the 2022 Winter Olympics in Beijing,the XC skiing,biathlon and nordic combined events will be held at altitudes of~1700 m above sea level,possibly in cold environmental conditions and while requiring adjustment to several time zones.However,the ongoing COVID-19 pandemic may lead to sub-optimal preparations.The current commentary provides the following evidence-based recommendations for the Olympic preparations:make sure to have extensive experience of training(>60 days annually)and competition at or above the altitude of competition(~1700 m),to optimize and individualize your strategies for acclimatization and competition.In preparing for the Olympics,10-14 days at~1700 m seems to optimize performance at this altitude effectively.An alternative strategy involves two-three weeks of training at>2000 m,followed by 7-10 days of tapering off at~1700 m.During each of the last 3 or 4 days prior to departure,shift your sleeping and eating schedule by 0.5-1 h towards the time zone in Beijing.In addition,we recommend that you arrive in Beijing one day earlier for each hour change in time zone,followed by appropriate timing of exposure to daylight,meals,social contacts,and naps,in combination with a gradual increase in training load.Optimize your own individual procedures for warming-up,as well as for maintaining body temperature during the period between the warm-up and competition,effective treatment of asthma(if necessary)and pacing at~1700 m with cold ambient temperatures.Although we hope that these recommendations will be helpful in preparing for the Beijing Olympics in 2022,there is a clear need for more solid evidence gained through new sophisticated experiments and observational studies.
文摘The present review deals with the current scientific knowledge related with ski jump landing.A specific focus is given on the landing biomechanics,the methods utilized for its analysis and the injuries connected to the landing phase.Despite the demonstrated importance for the safety and the performance of ski jumpers,the landing and its preparation are rarely inves-tigated.In this paper,after having firstly described the execution of landing and its preparation and the reason why is impor-tant to analyze it,an overview of the current status of the research related to the landing biomechanics is reported(kinetics,kinematics,electromyographic activation,aerodynamics,computer simulation).The third part describes the methods and technologies utilized in literature to analyze the landing and its preparation(video cameras,inertial sensors,force insoles,wind tunnel and computer simulation).After that,an overview of the injuries related to landing is reported.The final section proposes future research in the field of biomechanics of ski jump landing in different fields,such as computer simulations,kinematic analysis,equipment development and biomechanics of female athletes.
基金supported by National Natural Science Foundation of China(No.31371199).
文摘Purpose The aim of this study was to investigate whether skeletal muscle-derived follistatin-like 1(FSTL1)reaches the heart and exerts the angiogenetic function in rats suffering myocardial infarctions(MI)after exercise intervention.Methods Forty-eight male adult Sprague-Dawley rats were randomly divided into four groups.MI was provoked by ligation of left anterior descending coronary artery.MI rats underwent adeno-associated virus injection of FST1 in tibialis anterior muscle and 4 weeks of resistance exercise via a tail-suspended incremental weight-climbing method(0-75%body weight,daily load increased by 10%;1 h/day,5 day/w).Heart function was evaluated by hemodynamics including LVSP,LVEDP and±dP/dt max;the cross-sectional area of muscle cells and myocardium fibrosis were analyzed by DiI and Masson’s stain-ing,respectively;the FSTL1 expression,endothelial cell proliferation and angiogenesis were visualized by immunofluores-cence staining;and protein expression was quantified by Western blotting.Results Resistance exercise reverted MI-induced skeletal muscle atrophy,increased muscle FSTL1 expression and stimulated skeletal muscle derived FSTL1 entering into the MI heart via blood circulation.The overexpression of skeletal muscle FSTL1 improved myocardial endothelial cell proliferation,increased small vessel density in the fibrotic border,inhibited myocardial fibrosis and improved heart function in the MI rats after the exercise intervention.Meanwhile,DIP2A-PI3K-Akt-mTOR,Erk1/2 and TGFβ-Smad2/3 pathways were activated in the myocardium.Conclusion Resistance exercise stimulates skeletal muscle derived FSTL1 to reach the myocardium which makes a positive contribution to cardioprotection in MI rat.
文摘This study aimed to determine the net energy expenditure(EENET)required for overground walking and running 1200 m in a sample of healthy adolescent boys and girls.A secondary purpose was to describe the effect of body composition on energy expenditure(EE)of walking versus running.Twenty healthy adolescents(9 boys,11 girls)aged 15.85±2.80 years performed 2 field tests in regular outdoor conditions:overground walking(1.64±0.17 m/s)and submaximal running(3.13±0.42 m/s),at a self-selected steady pace.EE was measured via indirect calorimetry.Paired sample t-tests were used to determine if there were differences between walking and running conditions and mean percentage differences were estimated for various physiological parameters.Differences in EENET between conditions were performed for both genders using a two(condition)by two(gender)analysis of variance repeated measures design,with fat free mass as a covariate.Speed increased by 90.43%between the 2 conditions,while the different components of EE increased by almost 20%.Running elicited a significantly greater EENET than walking for both genders;however,boys’and girls’EE did not differ significantly.When EENET was adjusted for fat free mass,there was a statistically significant condition×fat free mass effect.The findings in this study indicate that both adolescent boys and girls expend more energy during running than walking,without being affected by body composition.Body mass and fat free mass significantly correlated with EE only during running.In addition,the trained participants of the study optimized locomotion to minimize EE.
文摘Purpose The purpose of the study was to investigate the acute effect of a beginner martial art class and aerobic exercise on executive function(EF)in college-aged young adults.There is overwhelming evidence that demonstrates acute as well as long-term aerobic exercise improves EF.Nevertheless,there is limited research comparing externally paced exercise(EPE)to self-paced exercise(SPE)such as walking on improving EF.EPE requires greater cortical demand than SPE to execute a motor plan.Methods Eight men and eight women,aged 24.2±2.8 years,participated in a Repeated Measures Crossover Design.Pre-and post-testing of EF with the Stroop and Tower of London(ToL)and stress level were measured after each of the two 1-h conditions:the SPE consisted of a walk(aerobic exercise)and the EPE was a beginner martial art class.Results There were significant main effects for the martial art class for the Stroop’s mean reaction time for congruent trials(P=0.01)with a large-effect size.The mean reaction time for incongruent trials was significant(P=0.05)with a medium-effect size.The ToL’s mean solution time(P=0.003)and mean execution time(P=0.002)were also significant with large-effect sizes.Stress levels were not significantly improved following either condition.Conclusion The martial art class significantly improved all the major domains of EF,while aerobic exercise of a similar intensity did not demonstrate any measured significant changes.The physiological benefits of physical exercise are well documented;however,the cognitive enhancing capability of EPE should also be appreciated given the results of this study.
文摘Beijing will host the 2022 Winter Olympics,and China strengthens research on various aspects to allow their athletes to compete successfully in winter sport.Simultaneously,Government-directed initiatives aim to increase public participation in recreational winter sport.These parallel developments allow research to advance knowledge and understanding of the physiological determinants of performance and health related to winter sport.Winter sport athletes often conduct a substan-tial amount of training with high volumes of low-to-moderate exercise intensity and lower volumes of high-intensity work.Moreover,much of the training occur at low ambient temperatures and winter sport athletes have high risk of developing asthma or asthma-related conditions,such as exercise-induced bronchoconstriction.The high training volumes require optimal nutrition with increased energy and dietary protein requirement to stimulate muscle protein synthesis response in the post-exercise period.Whether higher protein intake is required in the cold should be investigated.Cross-country ski-ing is performed mostly in Northern hemisphere with a strong cultural heritage and sporting tradition.It is expected that innovative initiatives on recruitment and training during the next few years will target to enhance performance of Chinese athletes in classical endurance-based winter sport.The innovation potential coupled with resourcing and population may be substantial with the potential for China to become a significant winter sport nation.This paper discusses the physiological aspects of endurance training and performance in winter sport highlighting areas where innovation may advance in athletic performance in cold environments.In addition,to ensure sustainable development of snow sport,a quality ski patrol and rescue system is recommended for the safety of increasing mass participation.
基金The study was financially supported by the Swedish Olympic Committe and the Slovenian Research Agency within the research program fund P5-0147 Kinesiology of monostructural,polystructural and conventional sports.
文摘Although reliable feedback is crucial to improving the performance of competitive alpine skiers,the coach’s eye may not be sensitive enough to detect small,but highly significant“mistakes”.Monitoring of the performance of alpine ski racers by inertial motion units(IMU)has proven to be of value in this context and here we summarize practical and methodological aspects of this approach.Methodologically,the IMUs employed should combine high sampling frequencies with minimal signal drift.The sensors should be positioned to sense the movement of the bones in a given body segment while being pro-tected as much as possible against impact with the ski gates.The data obtained,often synchronized with input from Global Satellite Navigation Systems(GNSS),are usually refined utilizing advanced biomechanical models and other computerized approaches.In practice,the combination of inertial sensors and GNSS allows accurate monitoring of skiing kinematics(technique)and the movement of the skier’s center-of-mass,also allowing analysis of both whole-body vibrations(WBV)and loss of mechanical energy.Presentation of the findings to coaches and athletes can be facilitated by synchronizing them with video recordings.Recent advances in IMU technology,including miniaturization,wireless communication,direct stor-age of data in the cloud,and processing with artificial intelligence may allow these sensors,in-combination with GNSS,to become real-time virtual alpine ski coaches,perhaps the next step in the development of this sport.
基金supported in part by a grant from the National Sports Institute of Malaysia.
文摘Purpose This study aimed to investigate the relationships between vertical jump metrics and phases during a 60 m sprint.The variances in strength qualities between sprinters of different ability levels were also compared.Methods Eighteen young male elite sprinters(age:18.1±1.3 years;stature:1.72±0.07 m;body mass:66.3±6.2 kg)were assessed for squat(SJ),countermovement(CMJ),drop(DJ),and standing long jumps,a maximal load back-squat,and a 60-m sprint from a block-start.The relationships between sprint performances with all variables were analysed using correlation and multiple regression while discriminative parameters between fast(100 m time:~10.50 s)and slow(~11.00 s)sprint groups were assessed using independent t-tests.Results Higher associations existed between vertical jumps and longer sprint distances,especially between SJ height and relative peak power with 10 m(r=−0.47 and−0.47,respectively),30 m(−0.71 and−0.74),60 m(−0.76 and−0.81),10-30 m(−0.80 and−0.86),and 30-60 m(−0.78 and−0.84)sprint distances.Concurrently,variables such as relative maximal-strength,relative SJ parameters(height,peak force,and peak power),relative CMJ peak power,and reactive strength index(DJ from 35 cm height)had significant discriminative ability and correlations(P<0.05)with sprint distances involving maximal velocity and flying-start.Additionally,a combination of SJ height and relative maximal-strength during back-squat accounted for 75%of the variance in 60 m sprint times.Conclusions Relative measures of multiple strength metrics may provide better insight regarding factors that enhance sprint performance.Adequate maximal-strength,high explosive power,and reactive strength seem necessary to improve sprint performance in young male elite sprinters.
文摘Purpose Main purposes of pre-acclimatization by hypoxia conditioning(HC)are the prevention of high-altitude illnesses and maintenance of aerobic exercise performance.However,robust evidence for those effects or evidence-based guidelines for exposure strategies,including recommendations to ensure safety,are largely lacking.Therefore,we summarize the current knowledge on the physiology of acclimatization to hypoxia and HC with the aim to derive implications for pre-acclimatization strategies before going on high-altitude treks and expeditions.Methods Based on the literature search and personal experience,core studies and important observations have been selected in order to present a balanced view on the current knowledge of high-altitude illnesses and the acclimatization process,specifically focusing on pre-acclimatization strategies by HC.Results and Conclusions It may be concluded that in certain cases even short periods(e.g.,7 h)of pre-acclimatization by HC are effective,but longer periods(e.g.,>60 h)are needed to elicit more robust effects.About 300 h of HC(intermittently applied)may be the optimal preparation for extreme altitude sojourns,although every additional hour spent in hypoxia may confer further benefits.The inclusion of hypobaric exposures(i.e.,real altitude)in pre-acclimatization protocols could further increase their efficacy.The level of simulated altitude is progressively increased or individually adjusted ideally.HC should not be terminated earlier than 1-2 weeks before altitude sojourn.Medical monitoring of the pre-acclimatization program is strongly recommended.
文摘Purpose The purpose was to investigate whether an increased amount of training while carrying the rifle affects skiing in well-trained biathletes at submaximal and maximal workloads during a pre-season period lasting a minimum of 12 weeks.Methods Seventeen well-trained biathletes(9 females,8 males)were assigned to an intervention(IG,n=10)or control(CG,n=7)group.Before(T1)and after(T2)the training intervention all participants performed,using treadmill roller-skiing,a submaximal test without the rifle on one day and two submaximal workloads and a maximal time trial(TT)with the rifle on a subsequent day.Between T1 and T2 all participants performed a minimum of 12 weeks of normal training,the only difference between groups being that IG performed more of their training sessions carrying the rifle.Results IG performed more training compared to CG(15.4±1.1 vs.11.2±2.6 h/week,P<0.05),including a higher amount of training with the rifle(3.1±0.6 vs.1.1±0.3 h/week,P<0.001).Speed at 4 mmol/L of blood lactate increased significantly for CG from T1 to T2(P=0.028),while only tended to increase for IG(P=0.058).Performance during the TT,VO2max and the aerobic metabolic rate increased significantly from T1 to T2,although the differences disappeared when including the speed at baseline as a covariate.Conclusion According to the present results,increasing training while carrying the rifle by 2 h/week does not appear to improve skiing performance in well-trained biathletes.In addition,physiological markers at submaximal and maximal intensities while carrying the rifle were not affected after the training intervention.
文摘Cross-country(XC)ski races involve a variety of formats,two different techniques and tracks with highly variable topography and environmental conditions.In addition,XC skiing is a major component of both Nordic combined and biathlon competi-tions.Research in this area,both in the laboratory and field,encounters certain difficulties that may reduce the reliability and validity of the data obtained,as well as complicate comparisons between studies.Here,13 international experts propose specific guidelines designed to enhance the quality of research and publications on XC skiing,as well as on the biathlon and Nordic combined skiing.We consider biomechanical(kinematic,kinetic and neuromuscular)and physiological methodology(at the systemic and/or muscle level),providing recommendations for standardization/control of the experimental setup.We describe the types of measuring equipment and technology that are most suitable in this context.Moreover,we also deal with certain aspects of nomenclature of the classical and skating sub-techniques.In addition to enhancing the quality of stud-ies on XC skiing,Nordic combined and biathlon,our guidelines should also be of value for sport scientists and coaches in other disciplines where physiological and/or biomechanical measurements are performed in the laboratory and/or outdoors.
文摘Purpose To challenge current conventions in paediatric sport science and use data from recent longitudinal studies to elu-cidate the development of aerobic and anaerobic fitness,with reference to youth athletes.Methods(1)To critically review the traditional practice of ratio scaling physiological variables with body mass and,(2)to use multiplicative allometric models of longitudinal data,founded on 1053(550 from boys)determinations of 10-17-year-olds’peak oxygen uptake(VO2)and 763(405 from boys)determinations of 11-17-year-olds’peak power output(PP)and mean power output(MP),to investigate the development of aerobic and anaerobic fitness in youth.Results The statistical assumptions underpinning ratio scaling of physiological variables in youth are seldom met.Multiplicative allometric modelling of longitudinal data has demonstrated that fat free mass(FFM)acting as a surrogate for active muscle mass,is the most powerful morphological influence on PP,MP,and peak VO2.With FFM appropriately controlled for,age effects remain significant but additional,independent effects of maturity status on anaerobic and aerobic fitness are negated.Conclusions Ratio scaling of physiological variables with body mass is fallacious,confounds interpretation of the develop-ment of anaerobic and aerobic fitness,and misleads fitness comparisons within and across youth sports.Rigorous evalua-tion of the development of anaerobic and aerobic fitness in youth requires longitudinal analyses of sex-specific,concurrent changes in age-and maturation-driven morphological covariates.Age and maturation-driven changes in FFM are essential considerations when evaluating the physiological development of youth athletes.
文摘Purpose Cystic Fibrosis(CF)is a multisystem disease associated with symptoms such as dyspnoea,tachycardia and tachyp-nea that may be related to changes in autonomic function and sensitive to improvement following inspiratory muscle training(IMT).The aim of the present study was to investigate the effect of IMT on heart rate variability(HRV)and respiratory function in children.Methods Five CF and five matched controls(40%boys)performed a 4-weeks IMT programme,involving 30 breaths,twice a day.Weeks 1-2 of training were set at 40%of a participant's maximal strength index(S.Index),with week's 3-4 set at 50%.Participants wore an ActiHeart for three consecutive days at baseline and post-intervention and indices of HRV were derived.Standard measures of lung function were obtained along with health-related quality of life(HRQoL)using the CF-specific questionnaire(CFQ-R).Results IMT elicited clinically meaningful increases in respiratory muscle strength and respiratory symptom domain scores,but no improvements in respiratory volume,irrespective of group.Similarly,no significant improvements were found in HRQoL despite 62.5%of the population increased their HRQoL score.Post-intervention,CF participants showed a clinically meaningful decrease in the very low frequency(VLF)domain.Conclusion These results may indicate clinically meaningful changes in HRV and inspiratory muscle strength following a 4-week IMT intervention,although a more powerful study is required to draw further conclusions.Indeed,the trends for improved HRQoL support the need for such studies to ascertain the potential therapeutic role of IMT in those with CF.
基金support from National Institutes of Health/NIAMS Grants U01AR067997,R01 AR070474,R01 AR056259-01industry sponsored research funding related to brain injury prevention and assessment with Q30 Innovations,LLC and ElMinda,Ltd,and book royalties from Human KineticsThe other authors have indicated they have no financial relationships relevant to this article to disclose.
文摘Purpose To quantify the effects of an externally worn collar device for mitigating the influence of repetitive head impacts on alterations to diffusion tensor imaging(DTI)metrics of white matter.Methods Fifteen female high-school soccer athletes(age:14.00-16.98 yrs)completed pre-and post-season DTI over two consecutive years,including measures of diffusivity,changes in which may be associated with brain dysfunction.The collar was worn during year 1(Yr1)but not during year 2(Yr2).Athlete exposures(AEs)and head impact exposure were recorded over the competitive seasons.Results There were no significant differences in AEs or head impact exposures between Yr1 and Yr2(P>0.05).In Yr2,there was significant pre-to post-season mean diffusivity and/or axial diffusivity reduction in multiple WM regions(cor-rected P<0.05).Pre-to post-season mean diffusivity,axial diffusivity,and radial diffusivity decreases were 3.04%±2.53%,2.97%±2.19%,and 3.37%±3.34%,respectively,significantly greater than pre-to post-season changes in Yr1(mean dif-fusivity:-0.31%±1.78%,P=0.0014;axial diffusivity:-0.02%±2.25%,P=0.0014;radial diffusivity:-0.63%±2.10%,P=0.0030).Conclusions Mild bilateral compression to athletes'internal jugular vein through collar application may have increased intracranial blood volume and spatially redistributed head-impact-derived brain energy absorption.However,future research is needed to elucidate the potential clinical significance of WM changes of various degrees.Clinical trails registration NCT03014492.
文摘Purpose To investigate the physiological responses to low-load,superset resistance training(two exercises for the agonist and antagonist muscles performed without rest between exercises)to failure using elastic bands.Methods Twenty-three athletes were randomized to either a superset group(S,n=12,average age:19.8±1.5 years)or a traditional set group(T,n=11,average age:20.1±1.4 years).Strength,cross-sectional area(CSA)and muscular endurance of the biceps and triceps brachii were assessed before and after 8 weeks.Acute responses(muscle thickness)were measured during one testing session.Results Muscle thickness of the biceps significantly increased in both T group(P<0.05)and S group(P<0.05)after a single bout of Training.The triceps did not show significant increases in either T group(P>0.05)or S group(P>0.05).Blood lactate also increased in both groups after one bout of training(T:from 1.3±0.3 to 5.5±2.4 mmol/L,S:from 1.4±0.5 to 5.1±1.5 mmol/L,P<0.05).After 8-week training,both groups showed significant increases in the biceps(T:13.2%±5.0%;S:12.9%±7.3%,P<0.05)and triceps(T:9.5%±9.3%,S:4.8%±4.1%,P<0.05)without differences between groups.Increases in one repetition maximum for the bench press(7.8%±6.5%,P<0.05)and maximal voluntary contraction for the arm extensors(9.3%±11.6%,P<0.05)were observed for the T group only.Increases in muscular endurance were observed only in the S group for the bench press(26.0%±19.1%,P<0.05)and the barbell curl(17.2%±16.6%,P<0.05).Conclusions Superset training may enhance muscular endurance while attenuating maximal strength gains.There does not appear to be a hypertrophic benefit to performing superset training,but it may provide a time-efficient strategy to achieve adaptations in muscle mass.
文摘Purpose To evaluate the effects of acute moderate-intensity exercise on ecological memory,as assessed from a face-name memory task.Methods A two-arm,parallel-group,randomized controlled intervention was employed.Participants(N=40;Mage=20.8 years)were randomized into a seated control task or a bout of acute moderate-intensity treadmill exercise(15-min).Thereafter,participants completed a 3-phase face-name memory task,involving a study phase and two test phases(immediate and delayed recall,with the delay occurring 15 min after the immediate recall).Results For the immediate memory recall,the mean(SD)scores for the exercise and control conditions,respectively,were 6.60(2.5)and 6.20(2.5).For the 15-min delayed assessment,the respective scores were 6.25(2.6)and 5.75(1.9).There was a significant main effect for time(F=4.06,P=0.05, η^(2)_(p)=0.10).However,there were no main effects for group(F=0.33,P=0.56, η^(2)_(p)=0.01)or time by group interactions(F=0.12,P=0.72, η^(2)_(p)=0.003).Conclusions Despite the exercise group having slightly higher immediate and delayed face-name memory scores,we did not observe robust evidence of acute exercise enhancing face-name memory performance.
文摘Purpose To analyze the inter-limb coordination patterns and energy recovery of elite cross-country skiers performing double poling(DP).Methods Thirty-three elite athletes in three track sections of FIS-WC races,with different slopes(2°,0°and−1.5°).Stereo vision capture system(50 Hz cameras)and 3D analysis were used to extract:kinematic parameters(center of gravity,veloc-ity);joint angles and angular velocities;energy(potential and kinetic)and energy recovery indices R% and R(t)during the entire DP cycle and within poling(R_(pol))and swing phase(R_(swi)).Results Average race velocity of the centre of gravity(V_(ave))significantly varied according to slopes(5.4,7.3 and 8.3 m/s).This correlated with differences in the angular velocities of the most relevant joints.Elbow flexion angular velocity in the early portion of poling phase was higher according to the slope variations(−137,−171 and−202 deg/s,for the slopes 2°,0°and−1.5°,respectively),indicating the possible modulation of muscular stretch shortening cycle(SSC).A similar trend was observed for shoulder angular velocity which increased during poling phase,and for knee extension velocity during swing phase,and for knee extension velocity during swing phase.R%decreased significantly for the−1.5°slope(32%and 24%vs.15%);R(t)was higher for the Rswi.Significant differences were observed in trunk-elbow,trunk-shoulder,trunk-knee and elbow-shoulder patterns for the−1.5°slope with respect to the others.Conclusions Despite the modest variation of the track’s slope,the effects on propulsion and recovery strategies were different.
文摘Purpose To investigate the effects of 4 weeks high-intensity interval training in hypoxia on aerobic and anaerobic perfor-mance of 3-on-3 basketball players.Methods In a randomised controlled trial,15 female basketballers completed eight 1-h high-intensity training sessions in either normobaric hypoxia(hypoxic group n=8,altitude 3052 m)or normoxia(normoxic group n=7,sea-level).Results After training,the hypoxic group increased their 1-min all-out shuttle run distance by 2.5%±2.3%(mean±95%CI,d=0.83,P=0.04),compared to the normoxic group 0.2%±2.3%(d=0.06,P=0.8),with the difference between groups being clinically worthwhile but not statistically significant(d=0.77,P=0.1).Distance covered in the Yo-Yo intermittent recovery test tended to increase in the hypoxic(32.5%±39.3%,d=1.0,P=0.1)but not normoxic group(0.3%±24.5%,d=0.08,P=0.9),with a non-significant change between groups(d=0.9,P=0.2).Compared to normoxia,the hypoxic group significantly increased subjective markers of stress(d=0.53,P=0.005),fatigue(d=0.43,P=0.005),and muscle soreness(d=0.46,P=0.01),which resulted in a lower perceived training performance in the hypoxic compared to the normoxic group(d=0.68,P=0.001).Conclusion High-intensity interval training under hypoxic conditions likely improved 1-min all-out shuttle run ability in female basketball 3-on-3 players but also increased subjective markers of stress and fatigue which must be taken into con-sideration when prescribing such training.
文摘Purpose Isometric strength training (IST) with rapid non-sustained contraction (RIST) is effective in improving the ability to generate force rapidly.However,the neuromuscular adaptation of IST with sustained contraction (SIST) and RIST is not known.Therefore,the aim of the study was to compare the neuromuscular adaptations of RIST with SIST.Methods Thirty-three national floorball players (23.9 ± 3.1 years old;1.69± 0.08 m;64.6± 11.1 kg) were recruited for this study.Pre-and post-test included countermovement jump (CMJ),30-m sprint (TT30),isometric squat at 90° (ISqT90) and 120° (ISqT120) knee angles.They were randomly assigned to either control (Con) (n =9),RIST (n =12) or SIST (n =12)group and performed 12 sessions of intervention training.All groups performed the same sets of exercises,but RIST and SIST had to perform ISqT with and without sustained contraction,respectively.Results Time × group effect for CMJ height (P =0.01,η2p=0.25),peak force (PF) (P =0.03,η2p =0.22) and rate of force development (RFD) (P =0.02,η2p =0.22) obtained from ISqT 120 were noted.A main effect for time was observed in CMJ height,PF obtained from ISqT90 and ISqT120,and RFD obtained from ISqT90 (P < 0.01,0.27 < η2p < 0.57).There was greater improvement in TT30 (P =0.043,d =3.00),ISqT90 PF (P =0.034,d =3.12),ISqT 120 PF (P =0.003,d =4.54) and ISqT120 RFD (P=0.033,d=1.36) in the SIST than the Con group.Conclusion SIST was more effective in improving strength and dynamic performance as compared to RIST,making it a viable training method to enhance dynamic performances.
