The relationship between pre-season fitness testing and injury in elite junior Australian football players. Multivariate modelling of subjective and objective monitoring data improve the detection of non-contact injury risk in elite Australian footballers. Identifying high risk loading conditions for in-season injury in elite Australian football players. The Trainability of Adolescent Soccer Players to Brief Periodized Complex Training. The New Zealand rugby injury and performance project. VI. A prospective cohort study of risk factors for injury in rugby union football The effect of short-term interval training during the competitive season on physical fitness and signs of fatigue: a crossover trial in high-level youth football players. Monitoring Changes in Rugby League Players' Perceived Stress and Recovery during Intensified Training Perceived risk, risk taking, estimation of ability and injury among adolescent sport participants. Performance Enhancement Effects of Fédération Internationale de Football Association’s “The 11+” Injury Prevention Training Program in Youth Futsal Players Effect of football or strength training on functional ability and physical performance in untrained old men. Positive effects of 1-year football and strength training on mechanical muscle function and functional capacity in elderly men Performance, biochemical, and endocrine changes during a competitive football game. [Improving physical fitness in adolescents through a school-based intervention: the EDUFIT study]. Maturity-associated variation in the growth and functional capacities of youth football (soccer) players 13–15 years High chronic training loads and exposure to bouts of maximal velocity running reduce injury risk in elite Gaelic football. Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes Importance of Various Training-Load Measures in Injury Incidence of Professional Rugby League Athletes.
OBJECTIVES Australian Football ( AF ) is a collision sport containing high injury rates in junior competition . Successful performance at the elite junior level not only requires superior specific football knowledge and skills , but also well developed fitness qualities . However , no studies have examined the link between physical fitness qualities and injury in AF . DESIGN Prospect i ve cohort . METHODS Injury data were collected through the use of a Player Movement Record ( PMR ) and a st and ardized Injury Report Form ( IRF ) . Fitness test data was collected during the pre-season of the 2010 and 2011 seasons . RESULTS 382 players consented to participate in the study . The cohort experienced an injury incidence rate of 24.29/st and ardized club ( 40 players/club ) . A faster 5-m sprint was associated with ' injury status ' ( p=0.016 ) and a ' knee ' region ( p≤0.001 ) injury . A faster planned agility score was associated with an increased risk of a ' hip/groin/thigh ' region ( p=0.010 ) injury , and specifically a ' quadriceps strain ' ( p=0.005 ) . A lower 20-m shuttle run was associated with an increased risk of a ' shin/ankle/foot ' ( p=0.045 ) injury . Increased injury severity was associated with a higher left foot running vertical jump ( VJ ) ( p=0.040 ) , and faster 5-m sprint ( p=0.043 ) . CONCLUSIONS Lower aerobic endurance , faster 5-m acceleration and greater planned agility were associated with an increased risk of various injury types in elite junior AF players . Furthermore , a higher left foot running VJ and faster 5-m acceleration were associated with injury severity . These results may largely relate to a greater work capacity placing a higher load upon the musculoskeletal system in contact and non-contact situations OBJECTIVES To assess the association between workload , subjective wellness , musculoskeletal screening measures  and non-contact injury risk in elite Australian footballers . DESIGN Prospect i ve cohort study . METHODS Across 4 seasons in 70 players from one club , cumulative weekly workloads ( acute ; 1 week , chronic ; 2- , 3- , 4-week ) and acute : chronic workload ratio 's ( ACWR : 1-week load/average 4-weekly load ) for session-Rating of Perceived Exertion ( sRPE ) and GPS-derived distance and sprint distance were calculated . Wellness , screening and non-contact injury data were also documented . Univariate and multivariate regression models determined injury incidence rate ratios ( IRR ) while accounting for interaction/moderating effects . Receiver operating characteristics determined model predictive accuracy ( area under curve : AUC ) . RESULTS Very low cumulative chronic ( 2- , 3- , 4- week ) workloads were associated with the greatest injury risk ( univariate IRR=1.71 - 2.16 , 95 % CI=1.10 - 4.52 ) in the subsequent week . In multivariate analysis , the interaction between a low chronic load and a very high distance ( adj-IRR=2.60 , 95 % CI=1.07 - 6.34 ) or low sRPE ACWR ( adj-IRR=2.52 , 95 % CI=1.01 - 6.29 ) was associated with increased injury risk . Subjectively reporting " yes " ( vs. " no " ) for old lower limb pain and heavy non-football activity in the previous 7 days ( multivariate adj-IRR=2.01 - 2.25 , 95 % CI=1.02 - 4.95 ) and playing experience ( > 9 years ) ( multivariate adj-IRR=2.05 , 95 % CI=1.03 - 4.06 ) was also associated with increased injury risk , but screening data were not . Predictive capacity of multivariate models was significantly better than univariate ( AUCmultivariate=0.70 , 95 % CI 0.64 - 0.75 ; AUCunivariate range=0.51 - 0.60 ) . CONCLUSIONS Chronic load is an important moderating factor in the workload-injury relationship . Low chronic loads coupled with low or very high ACWR are associated with increased injury risk OBJECTIVES To examine different timeframes for calculating acute to chronic workload ratio ( ACWR ) and whether this variable is associated with intrinsic injury risk in elite Australian football players . DESIGN Prospect i ve cohort study . METHODS Internal ( session rating of perceived exertion : sRPE ) and external ( GPS distance and sprint distance ) workload and injury data were collected from 70 players from one AFL club over 4 seasons . Various acute ( 1 - 2 weeks ) and chronic ( 3 - 8 weeks ) timeframes were used to calculate ACWRs : these and chronic load categories were then analysed to determine the injury risk in the subsequent month . Poisson regression with robust errors within a generalised estimating equation were utilised to determine incidence rate ratios ( IRR ) . RESULTS Altering acute and /or chronic timeframes did not improve the ability to detect high injury risk conditions above the commonly used 1:4 week ACWR . Twenty-seven ACWR/chronic load combinations were found to be " high risk conditions " ( IRR>1 , p<0.05 ) for injury within 7 days . Most ( 93 % ) of these conditions occurred when chronic load was low or very low and ACWR was either low ( < 0.6 ) or high ( > 1.5 ) . Once a high injury risk condition was entered , the elevated risk persisted for up to 28 days . CONCLUSIONS Injury risk was greatest when chronic load was low and ACWR was either low or high . This heightened risk remained for up to 4 weeks . There was no improvement in the ability to identify high injury risk situations by altering acute or chronic time periods from 1:4 weeks PURPOSE To investigate the effect of a complex , short-term strength/power training protocol on performance and body composition of elite early adolescent soccer players . METHODS Twenty-two players ( 14 - 15 y ) were r and omly assigned to ( 1 ) an experimental group ( N = 12 ; participated in a 5-wk training protocol with traditional multijoint power resistance exercises , Olympic-style lifts , plyometric drills , and speed work ; 4 times per week ) or ( 2 ) a control group ( N = 10 ) . Strength and power performance ( jumping , speed , change of direction , repeated sprint ability , endurance , isokinetic strength of knee flexors and extensors , maximal strength in various lifts , and speed-endurance ) were evaluated pretraining and posttraining . RESULTS Cessation of training for 5 weeks in the control group induced a marked performance deterioration ( ∼5%-20 % ) . Training not only prevented strength performance deterioration but also increased it ( ∼2%-30 % ) . Endurance and repeated sprint ability declined to a smaller extent in experimental group compared with control group ( 15 % vs 7.5 % ) . Isometric strength and body composition remained unaltered in both groups . CONCLUSIONS Results demonstrate that ( 1 ) young players exhibit a high level of trainability of their strength/power performance ( but not endurance ) in response to a short-term complex training protocol during early adolescence , ( 2 ) Olympic-style lifts are characterized by increased safety in this age group and appear to be highly effective , ( 3 ) lifts incorporating a hip thrust result in increased strength of both knee extensors and flexors , ( 4 ) cessation of training for only 5 weeks results in marked deterioration of strength/power and endurance performance , and ( 5 ) improvement of strength/power performance may be related to neural-based adaptation as body composition remained unaffected Objectives —Although the nature of rugby injury has been well documented , little is known about key risk factors . A prospect i ve cohort study was undertaken to examine the association between potential risk factors and injury risk , measured both as an injury incidence rate and as a proportion of the playing season missed . The latter measure incorporates a measure of injury severity . Methods —A cohort of 258 male players ( mean ( SD ) age 20.6 ( 3.7 ) years ) were followed through a full competitive season . At a preseason assessment , basic characteristics , health and lifestyle patterns , playing experience , injury experience , training patterns , and anthropometric characteristics were recorded , and then a battery of fitness tests were carried out . Results —A multiple regression model identified grade and previous injury experience as risk factors for in season injury , measured as an injury incidence rate . A second model identified previous injury experience , hours of strenuous physical activity a week , playing position , cigarette smoking status , body mass index , years of rugby participation , stress , aerobic and anaerobic performance , and number of push ups as risk factors for in season injury , measured as proportion of season missed . Conclusions —The findings emphasise the importance of previous injury as a predictor of injury incidence and of missing play . They also show the importance of considering both the incidence rate and severity of injury when identifying risk factors for injury in sport PURPOSE To analyze performance and fatigue effects of small-sided games ( SSG ) vs high-intensity interval training ( HIIT ) performed during a 4-wk in-season period in high-level youth football . METHODS Nineteen players from 4 youth teams ( 16.5 [ SD 0.8 ] y , 1.79 [ 0.06 ] m , 70.7 [ 5.6 ] kg ) of the 2 highest German divisions completed the study . Teams were r and omly assigned to 1 of 2 training sequences ( 2 endurance sessions per wk ) : One training group started with SSG , whereas the other group conducted HIIT during the first half of the competitive season . After the winter break , training programs were changed between groups . Before and after the training periods the following tests were completed : the Recovery-Stress Question naire for Athletes , creatine kinase and urea concentrations , vertical-jump height ( countermovement jump [ CMJ ] , drop jump ) , straight sprint , agility , and an incremental field test to determine individual anaerobic threshold ( IAT ) . RESULTS Significant time effects were observed for IAT ( + 1.3 % , η(p)(2 ) = .31 ) , peak heart rate ( -1.8 % , η(p)(2 ) = .45 ) , and CMJ ( -2.3 % , η(p)(2 ) = .27 ) , with no significant interaction between groups ( P > .30 ) . Players with low baseline IAT values ( + 4.3 % ) showed greater improvements than those with high initial values ( ± 0.0 % ) . A significant decrease was found for total recovery ( -5.0 % , η(p)(2 ) = .29 ) , and an increase was found for urea concentration ( + 9.2 % , η(p)(2 ) = .44 ) . CONCLUSION Four weeks of in-season endurance training can lead to relevant improvements in endurance capacity . The decreases in CMJ height and total-recovery score together with the increase in urea concentration might be interpreted as early signs of fatigue . Thus , the danger of overtaxing players should be considered This study assessed whether the Recovery-Stress Question naire for Athletes ( RESTQ-Sport ) could be used to monitor changes in perceived stress and recovery during intensified training of rugby league players . 20 semiprofessional rugby league players were divided into two equal groups r and omly assigned to complete 6 wk . of Normal Training or Intensified Training , each followed with a 7-day taper . Multistage Fitness Test performance and RESTQ – Sport measures were taken at the beginning , at 2-wk . intervals , and at the end of the training period . Endurance significantly decreased with Intensified Training and returned to baseline levels following the taper , while remaining unchanged in the Normal Training group . The RESTQ – Sport scores with training were positively related to stress subscale scores ( Fatigue , Disturbed Breaks , and General Stress ) and recovery subscale measures ( Success , Physical Recovery , Being in Shape , Self-efficacy , Social Relaxation , General Well-being , and Sleep Quality ) decreasing in the Intensified Training group and then normalising following the taper ( Stress subscales : Fatigue and General Stress , and Recovery subscales : Physical Recovery and General Well-being ) . The RESTQ – Sport is a practical psychometric tool for monitoring responses to training in team-sport athletes OBJECTIVE To determine the predictive validity of perceived risk , risk taking , estimation of ability , overefficacy , and previous injuries on actual injury among adolescents in sport ; and to examine sex differences on these factors . METHODS A cohort of 260 ( 148 male , 112 female ) soccer players aged 11 to 14 years participated in a 3-month prospect i ve injury study . Preseason written measures included self-reported perceived risk , previous injuries , risk taking and estimation of ability . RESULTS Low levels of perceived risk and estimation of ability were associated with a significant increase in risk of injury , with odds ratios ( ORs ) ranging from 3.77 - 7.92 . Positive relationships between injury and both estimation of ability and overestimation of ability were supported . Estimation of ability was also positively related to risk taking . In this study , however , risk taking was not directly related to injury , nor were previous injuries . Girls reported higher levels of perceived risk and lower levels of risk taking than boys . However , boys and girls reported similar estimation of ability and overestimation of ability and subsequently incurred similar numbers of injuries . CONCLUSIONS Perceived risk and estimation of ability represent significant psychological risk factors for injury in adolescent sports . Sex differences in perceived risk , risk taking , and previous injuries should be considered when developing environmental and behavioral injury-prevention programs Objective : To evaluate if Fédération Internationale de Football Association ’s “ The 11 + ” injury prevention program improves physical fitness and technical performance in youth futsal players . Design : R and omized cohort study . Setting : Futsal club . Participants : Thirty-six futsal players ( 17.3 ± 0.7 years ) . Intervention : Players were r and omized to an intervention group ( n = 18 ) or a control group ( n = 18 ) . Intervention group performed “ The 11 + ” twice per week for 12 weeks . Main Outcome Measures : Isokinetic testing to access maximal quadriceps ( Q ) and hamstring ( H ) strength , vertical jump ( squat jump , SJ ; countermovement jump , CMJ ) , 5-m and 30-m sprint , agility , slalom , and balance performances were also measured . Results : Intervention group increased ( P < 0.05 ) quadriceps concentric ( 14.7%-27.3 % ) and hamstrings concentric ( 9.3%-13.3 % ) and eccentric ( 12.7 % ) peak torque . Intervention group improved functional H : Q ratio by 1.8 % to 8.5 % ( P < 0.05 ) . Intervention group improved ( P < 0.05 ) SJ ( 13.8 % ) and CMJ ( 9.9 % ) and 5-m and 30-m sprint ( 8.9 % and 3.3 % , respectively ) , agility ( 4.7 % ) , and slalom ( 4.8 % ) performances . Intervention group also improved balance , by decreasing the number of falls by 30 % in the nondominant limb . No changes were observed in control group . Conclusions : The results suggest that " The 11 + " can be used as an effective conditioning means for improving physical fitness and technical performance of youth futsal players The effects of 16 weeks of football or strength training on performance and functional ability were investigated in 26 ( 68.2 ± 3.2 years ) untrained men r and omized into a  football ( FG ; n = 9 ) , a strength training ( ST ; n = 9 ) , or a control group ( CO ; n = 8) . FG and ST trained 1.6 ± 0.1 and 1.5 ± 0.1 times per week , respectively , with higher ( P < 0.05 ) average heart rate ( HR ) ( ∼140 vs 100 bpm ) and time > 90%HRmax ( 17 vs 0 % ) in FG than ST , and lower ( P < 0.05 ) peak blood lactate in FG than ST ( 7.2 ± 0.9 vs 10.5 ± 0.6 mmol/L ) . After the intervention period ( IP ) , VO₂ max ( 15 % ; P < 0.001 ) , cycle time to exhaustion ( 7 % ; P < 0.05 ) , and Yo-Yo Intermittent Endurance Level 1 performance ( 43 % ; P < 0.01 ) were improved in FG , but unchanged in ST and CO . HR during walking was 12 % and 10 % lower ( P < 0.05 ) in FG and ST , respectively , after IP . After IP , HR and blood lactate during jogging were 7 % ( P < 0.05 ) and 30 % lower ( P < 0.001 ) in FG , but unchanged in ST and CO . Sit-to-st and performance was improved ( P < 0.01 ) by 29 % in FG and 26 % in ST , but not in CO . In conclusion , football and strength training for old men  improves functional ability and physiological response to submaximal exercise , while football additionally elevates maximal aerobic fitness and exhaustive exercise performance Purpose A decline in physical capacity takes place with increasing age that negatively affects overall physical function including work ability and the ability to perform typical activities of daily living ( ADL ) . The overall aim of the present study was to determine the neuromuscular adaptations to long-term ( 1 year ) football and strength training in older untrained adults , and to assess the concurrent effect on functional ADL capacity . Methods Twenty-seven healthy elderly males ( 68.2 ± 3.2 years ) were r and omly assigned to 12 months of either recreational football training ( FT : n = 10 ) , strength training ( ST : n = 9 ) or served as inactive controls ( CON : n = 8) . Recreational football training consisted of small-sided training sessions whereas strength training consisted of high intensity exercises targeting the lower extremity and upper body . Maximal thigh muscle strength and rate of force development ( RFD ) were assessed with isokinetic dynamometry , while postural balance and vertical jumping performance were evaluated using force plate analysis . Furthermore , functional ability was evaluated by stair-ascent and chair-rising testing . Results A total of nine , nine and seven participants from FT , ST and CON , respectively , were included in the analysis . Both exercise regimens led to substantial gains in functional ability , evidence d by 24 and 18 % reduced stair-ascent time , and 32 and 21 % increased chair-rising performance in FT and ST , respectively ( all P < 0.05 ) . Long-term strength training led to increased concentric ( 14 % ; P < 0.01 ) and isometric ( 23 % ; P < 0.001 ) quadriceps and isometric hamstring strength ( 44 % ; P < 0.0001 ) , whereas football training mainly result ed in enhanced hamstring strength ( 18 % , P < 0.05 ) and RFD ( 89 % , P < 0.0001 ) . Conclusions Long-term ( 1 year ) strength training led to increased quadriceps and hamstring strength , whereas the adaptations to football training mainly included enhanced strength and rapid force capacity of the hamstring muscles . Gains in functional ability were observed in response to both training regimens , evidence d by reduced stair-ascent time and increased chair-rising performance  . Long-term football exercise and strength training both appear to be effective interventional strategies to improve factors of importance for ADL by counteracting the age-related decline in lower limb strength and functional capacity among old male adults . This could potentially be a way to improve work ability of senior workers PURPOSE This study represents the first time that anaerobic power performance was examined during an actual intercollegiate American football game . In addition , biochemical and endocrine responses also were examined to assess the physiological stress imposed by this competitive contest . METHODS Twenty-one members of a NCAA Division III football team were divided into two groups . Group one ( ST ) were  starters  ( N = 11 ) . The second group ( RS ) consisted of  red-shirt players ( N = 10 ) .  Blood sample s  were obtained 24 h ( Pre1 ) and 2.5 h ( Pre2 ) before the game and within 15 min of game conclusion ( IP ) . Anaerobic power measures were recorded approximately 10 min before kickoff ( pre ) and following the first ( Q1 ) , second ( Q2 ) , third ( Q3 ) , and fourth ( Q4 ) quarters . RESULTS Peak force ( PF ) and power ( PP ) in both squat and countermovement jumps decreased ( P < 0.05 ) from pre to Q2 in both ST and RS ; however , all variables returned to baseline levels by Q4 . When averaged across trials , PF and PP in both jumps were greater ( P < 0.05 ) in ST than RS . No significant changes in testosterone concentrations with respect to time or between groups were seen . Cortisol concentrations were significantly higher for ST at IP than RS . No significant changes in creatine kinase , alanine aminotransferase , urea , or uric acid were observed in either group from Pre2 to IP . In addition , no between group differences were seen in these variables . Myoglobin and aspartate aminotransferase significantly increased from Pre2 to IP in ST , and a significant difference in myoglobin concentrations was seen between the groups at IP . CONCLUSIONS Performance , biochemical , and endocrine changes in these NCAA Division III football players reflected the stress and muscle damage that occurs as a result of a competitive American football game INTRODUCTION AND OBJECTIVES Physical fitness level is a marker of cardiovascular health in young people . The aim of this study was to analyze the effects of a school-based intervention program , focused on increasing the volume and intensity of physical education ( PE ) sessions , on adolescents ' physical fitness . METHODS Sixty-seven adolescents ( 12 - 14 years old ) from three secondary school classes participated in a 16-week intervention . The classes were r and omly allocated to the control group , experimental group 1 ( EG1 ) or experimental group 2 ( EG2 ) . The control group received st and ard PE ( 2 sessions/week ) , the EG1 received 4 st and ard PE sessions/week and the EG2 received four high-intensity PE sessions/week . Aerobic fitness , muscle strength , speed-agility and flexibility were assessed using previously vali date d field-based tests before and after the intervention . RESULTS Doubling the number of PE sessions/week result ed in improvements in aerobic fitness and flexibility ( P=.008 and P=.04 , respectively ) . Further increases in the intensity of the sessions were related to improvements in speed-agility ( P<.001 ) . The maximal oxygen consumption increased by 3 and 5 mL/kg/min in the EG1 and EG2 , respectively . No differences were observed for muscle strength . CONCLUSIONS The results suggest that doubling the frequency of PE sessions is a sufficient stimulus to improve physical fitness , particularly aerobic fitness , which has been shown to be a powerful indicator of cardiovascular health in children and adolescents . Future studies involving larger sample sizes should confirm or refute these findings The objective was to estimate the contribution of experience , body size and maturity status to variation in the functional capacities of adolescent football ( soccer ) players . The sample included 69 players 13.2–15.1 years of age from three clubs which competed in the highest division for their age group in the first Portuguese national division . Height and weight were measured and stage of pubic hair development was assessed at clinical examination . The number of years of experience in football was obtained at interview . Three tests of functional capacity were administered :  30-m dash ( running speed ) , vertical jump ( explosive power )  and a yo-yo intermittent endurance test ( aerobic resistance )  . Multiple linear regression analysis was used to estimate the relative contributions of age , stage of sexual maturity , height , weight and years of formal training in football to the three indicators of functional capacity . Stage of puberty , body size and years of training accounted for 21 % to 50 % of the variance in the three tasks . Sexual maturity status was the primary contributor to the variance in the intermittent shuttle run , whereas weight and height were the primary contributors to the explained variance in the 30-m dash and vertical jump , respectively . In conclusion , biological maturity status significantly influences the functional capacity of adolescent football players 13–15 years of age . Training is a significant contributor to aerobic resistance , whereas weight and height are significant contributors to the sprint and vertical jump , respectively OBJECTIVES To examine the relationship between chronic training loads , number of exposures to maximal velocity , the distance covered at maximal velocity , percentage of maximal velocity in training and match-play and subsequent injury risk in elite Gaelic footballers . DESIGN Prospect i ve cohort design . METHODS Thirty-seven elite Gaelic footballers from one elite squad were involved in a one-season study . Training and game loads ( session-RPE multiplied by duration in min ) were recorded in conjunction with external match and training loads ( using global positioning system technology ) to measure the distance covered at maximal velocity , relative maximal velocity and the number of player exposures to maximal velocity across weekly periods during the season . Lower limb injuries were also recorded . Training load and GPS data were modelled against injury data using logistic regression . Odds ratios ( OR ) were calculated based on chronic training load status , relative maximal velocity and number of exposures to maximal velocity with these reported against the lowest reference group for these variables . RESULTS Players who produced over 95 % maximal velocity on at least one occasion within training environments had lower risk of injury compared to the reference group of 85 % maximal velocity on at least one occasion ( OR : 0.12 , p=0.001 ) . Higher chronic training loads ( ≥4750AU ) allowed players to tolerate increased distances ( between 90 to 120 m ) and exposures to maximal velocity ( between 10 to 15 exposures ) , with these exposures having a protective effect compared to lower exposures ( OR : 0.22 p=0.026 ) and distance ( OR=0.23 , p=0.055 ) . CONCLUSIONS Players who had higher chronic training loads ( ≥4750AU ) tolerated increased distances and exposures to maximal velocity when compared to players exposed to low chronic training loads ( ≤4750AU ) . Under- and over-exposure of players to maximal velocity events ( represented by a U-shaped curve ) increased the risk of injury Objective : To determine whether exposure to repetitive head impacts over a single season negatively affects cognitive performance in collegiate contact sport athletes . Methods : This is a prospect i ve cohort study at 3 Division I National Collegiate Athletic Association athletic programs . Participants were 214 Division I college varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration-time history of the head following impact , and 45 noncontact sport athletes . All athletes were assessed prior to and shortly after the season with a  cognitive screening battery ( ImPACT ) and a subgroup of athletes also were assessed with 7 measures from a neuropsychological test battery . Results : Few cognitive differences were found between the athlete groups at the preseason or postseason assessment s. However , a higher percentage of the contact sport athletes performed more poorly than predicted postseason on a measure of new learning ( California Verbal Learning Test ) compared to the noncontact athletes ( 24 % vs 3.6 % ; p < 0.006 ) . On 2 postseason cognitive measures ( ImPACT Reaction Time and Trails 4/B ) , poorer performance was significantly associated with higher scores on several head impact exposure metrics . Conclusion : Repetitive head impacts over the course of a single season may negatively impact learning in some collegiate athletes . Further work is needed to assess whether such effects are short term or persistent PURPOSE To investigate the ability of various internal and external training-load ( TL ) monitoring measures to predict injury incidence among positional groups in professional rugby league athletes . METHODS TL and injury data were collected across 3 seasons ( 2013 - 2015 ) from 25 players competing in National Rugby League competition . Daily TL data were included in the analysis , including  session rating of perceived exertion ( sRPE-TL ) , total distance ( TD ) , high-speed-running distance ( > 5 m/s ) , and high-metabolic-power distance ( HPD ; > 20 W/kg ) . Rolling sums were calculated , nontraining days were removed , and athletes ' corresponding injury status was marked as " available " or " unavailable . " Linear ( generalized estimating equations ) and nonlinear ( r and om forest ; RF ) statistical methods were adopted . RESULTS Injury risk factors varied according to positional group . For adjustables , the TL variables associated most highly with injury were 7-d TD and 7-d HPD , whereas for hit-up forwards they were sRPE-TL ratio and 14-d TD . For outside backs , 21- and 28-d sRPE-TL were identified , and for wide-running forwards , sRPE-TL ratio . The individual RF models showed that the importance of the TL variables in injury incidence varied between athletes . CONCLUSIONS Differences in risk factors were recognized between positional groups and individual athletes , likely due to varied physiological capacities and physical dem and s. Furthermore , these results suggest that robust machine-learning techniques can appropriately monitor injury risk in professional team-sport athletes
Of the few studies examining negative consequences associated with workloads , increases in training load led to increases in injury rates , while longer training duration was associated with a greater incidence of illness .
Conclusion The combined capacity for adolescent males to grow , train and improve physical performance highlights and underscores an exciting responsiveness to training in the football environment .
However , the capacity to train has some established barriers for adolescents experiencing high workloads , which could also result in negative consequences .
Background The expectation that training enhances performance is well explored in professional sport .
However , the additional challenges of physical and cognitive maturation may require careful consideration when determining workloads to enhance performance in adolescents .
Objective The objective of this study was to determine the state of knowledge on the relationship between workloads , physical performance , injury and /or illness in adolescent male football players .