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Purpose: This study investigated (1) the transition rate of elite world-class throwers, (2) the age of peak performance in either elite junior and/or elite senior athletes, and (3) if relative age effect (RAE) influences the chance of being considered elite in junior and/or senior category. Methods: The career performance trajectories of 5108 throwers (49.9% females) were extracted from the World Athletics database. The authors identified throwers who had reached the elite level (operationally defined as the World all-time top 50 ranked for each age category) in either junior and/or senior category and calculated the junior-to-senior transition rate. The age of peak performance and the RAE were also investigated. Results: The transition rate at 16 and 18 years of age was 6% and 12% in males and 16% and 24% in females, respectively. Furthermore, elite senior throwers reached their personal best later in life than elite junior throwers. The athletes of both genders considered elite in the junior category showed a large RAE. Interestingly, male athletes who reached the elite level in senior category also showed appreciable RAE. Conclusions: Only a few of the athletes who reach the top 50 in the world at 16 or 18 years of age manage to become elite senior athletes, underlining that success at the beginning of an athletic career does not predict success in the athlete’s senior career. Moreover, data suggest that being relatively older may confer a benefit across the whole career of male throwers.

PURPOSE To provide the first scrutiny of adult height prediction protocols based on automated Greulich-Pyle and Tanner-Whitehouse (TW) skeletal ages applied to elite youth soccer players from the Middle East. METHODS We examined the application of modified Bayley-Pinneau (BoneXpert®), TW-II, and TW-III protocols using mixed-longitudinal data available for 103 subjects (chronological age range, 19.4 to 27.9 yr) previously enrolled as academy student-athletes (annual screening range, one to six visits). Random-effects generalized additive models quantified the presence of systematic mean differences between actual versus predicted adult height. Effects were deemed practically equivalent based on the location of the confidence interval (95% CI) against a realistic difference value of Δ = ± 1 cm. Each model pooled residual standard deviation described the actual precision of height predictions and was used to calculate a 95% prediction interval. RESULTS The BoneXpert® method overpredicted adult height systematically at chronological ages in the range of approximately 13.5 to 14.5 yr (95% CI range, -1.9 to -1 cm) and Greulich-Pyle skeletal ages between 13.5 and 15 yr (95% CI range, -3.1 to -1 cm). Effects based on TW-II were practically equivalent across the chronological and skeletal age measurement ranges, with this protocol yielding adult height predictions with a precision (standard deviation) of approximately ±2.6 cm. The mean TW-III effects indicated systematic adult height overpredictions until the attainment of 14.5 and 15 yr of chronological age (95% CI range, -3.8 to -1.1 cm) and TW-III skeletal age (95% CI range: -5.2 to -2.3 cm), respectively. CONCLUSIONS Tanner-Whitehouse-II adult height prediction method provided more consistent estimates and can be considered the method of choice for talent development purposes in youth soccer players from the Middle East.

PurposeTo characterise hydration, cooling, body mass loss, and core (Tcore) and skin (Tsk) temperatures during World Athletics Championships in hot-humid conditions.MethodsMarathon and race-walk (20 km and 50 km) athletes (n=83, 36 women) completed a pre-race questionnaire. Pre-race and post-race body weight (n=74), Tcore (n=56) and Tsk (n=49; thermography) were measured.ResultsMost athletes (93%) had a pre-planned drinking strategy (electrolytes (83%), carbohydrates (81%)) while ice slurry was less common (11%; pcore was lower in athletes using ice vests (37.5°C±0.4°C vs 37.8°C±0.3°C, p=0.024). Tcore (pre-race 37.7°C±0.3°C, post-race 39.6°C±0.6°C) was independent of event, ranking or performance (p≥0.225). Pre-race Tsk was correlated with faster race completion (r=0.32, p=0.046) and was higher in non-finishers (did not finish (DNF); 33.8°C±0.9°C vs 32.6°C±1.4°C, p=0.017). Body mass loss was higher in men than women (−2.8±1.5% vs −1.3±1.6%, pConclusionMost athletes’ hydration strategies were pre-planned based on personal experience. Ice vests were the most adopted pre-cooling strategy and the only one minimising Tcore, suggesting that event organisers should be cognisant of logistics (ie, freezers). Dehydration was moderate and unrelated to performance. Pre-race Tsk was related to performance and DNF, suggesting that Tsk modulation should be incorporated into pre-race strategies.

ObjectivesTo describe the injury characteristics of male youth athletes exposed to year-round athletics programmes.MethodsInjury surveillance data were prospectively collected by medical staff in a cohort of youth athletics athletes participating in a full-time sports academy from 2014–2015 to 2018–2019. Time-loss injuries (>1 day) were recorded following consensus procedures for athletics. Athletes were clustered into five event groups (sprints, jumps, endurance, throws and non-specialised) and the number of completed training and competition sessions (athletics exposures (AE)) were calculated for each athlete per completed season (one athlete season). Injury characteristics were reported overall and by event groups as injury incidence (injuries per 1000 AE) and injury burden (days lost per 1000 AE).ResultsOne-hundred and seventy-eight boys (14.9±1.8 years old) completed 391 athlete seasons, sustaining 290 injuries. The overall incidence was 4.0 injuries per 1000 AE and the overall burden was 79.1 days lost per 1000 AE. The thigh was the most common injury location (19%). Muscle strains (0.7 injuries per 1000 AE) and bone stress injuries (0.5 injuries per 1000 AE) presented the highest incidence and stress fractures the highest burden (17.6 days lost per 1000 AE). The most burdensome injury types by event group were: bone stress injuries for endurance, hamstring strains for sprints, stress fractures for jumps, lesion of meniscus/cartilage for throws and growth plate injuries for non-specialised athletes.ConclusionAcute muscle strains, stress fractures and bone stress injuries were identified as the main injury concerns in this cohort of young male athletics athletes. The injury characteristics differed between event groups.

PurposeTo determine associations between thermal responses, medical events, performance, heat acclimation and health status during a World Athletics Championships in hot-humid conditions.MethodsFrom 305 marathon and race-walk starters, 83 completed a preparticipation questionnaire on health and acclimation. Core (Tcore; ingestible pill) and skin (Tskin; thermal camera) temperatures were measured in-competition in 56 and 107 athletes, respectively. 70 in-race medical events were analysed retrospectively. Performance (% personal best) and did not finish (DNF) were extracted from official results.ResultsPeak Tcore during competition reached 39.6°C±0.6°C (maximum 41.1°C). Tskin decreased from 32.2°C±1.3°C to 31.0°C±1.4°C during the races (pcore was not related to DNF (25% of starters) or medical events (p≥0.150), whereas Tskin, Tskin rate of decrease and Tcore-to-Tskin gradient were (p≤0.029). A third of the athletes reported symptoms in the 10 days preceding the event, mainly insomnia, diarrhoea and stomach pain, with diarrhoea (9% of athletes) increasing the risk of in-race medical events (71% vs 17%, pcore (39.4°C±0.4°C vs 39.8°C±0.7°C, p=0.044) and larger in-race decrease in Tskin (−1.4°C±1.0°C vs −0.9°C±1.2°C, p=0.060), than non-acclimated athletes. Although not significant, they also showed lower DNF (19% vs 30%, p=0.273) and medical events (19% vs 32%, p=0.179).ConclusionTskin, Tskin rate of decrease and Tcore-to-Tskin gradient were important indicators of heat tolerance. While heat-acclimated athletes ranked better, recent diarrhoea represented a significant risk factor for DNF and in-race medical events.

Purpose: This study aimed to describe the career performance progression of elite early- and later-success international swimmers competing in sprint events (ie, 50 and 100 m). Methods: The career performance trajectories of 6003 swimmers (50.9% females; 58,760 unique records) competing in the 4 swimming strokes were evaluated. Swimmers with early and later success were identified. The authors identified the top 50 all-time swimmers competing in junior career who did not reach the top 50 rankings in their senior career, and vice versa, and successful swimmers in both junior and senior career. Results: Early-success swimmers mainly achieved their peak performance before the age of 20 years and approximately 5–6 years before successful senior swimmers or approximately 3–4 years before successful swimmers both in junior and senior careers. The annual performance improvements of later-success swimmers were higher (about 1%–2%) until the age of 20 to 24 years, whereas early-success swimmers showed a performance stagnation at about 16 to 18 years in females and 19 to 20 years in males. Conclusions: Early-success swimmers who achieved peak performance at a young age were unable to maintain the same level of competitiveness in adulthood as they experienced a plateau in performance from the age of 20 years. The procedure of considering early performances solely for talent identification (and not the current rate of progression) might represent a limited approach for selecting future elite swimmers. Our results indicate that performance progression in the transition toward adult careers might be a strong indicator of performance potential.

Severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) is the virus causing Coronavirus disease 2019 (COVID-19). Since the World Health Organization declared the outbreak of pandemic on March 11, 2020, cases have been increasing around the World with more than 3-million deaths recorded and a daily number of COVID-19 cases 20 times higher than when the Olympics were postponed, at the time of writing. Governments adopted various lockdown measures forcing isolation for many weeks/months depending on the evolution of the disease in each country. The rapid transmission of the disease forced the Tokyo 2020 Olympics to be postponed for one year. Travel restrictions, quarantine requirements and isolation have been the norm for many athletes in preparation for the Olympic Games. Also, due to the measures put in place to reduce the spread of the disease, sporting facilities have been closed and competitions cancelled forcing athletes and their staff to find alternative solutions to maintain performance and continue preparing for the Olympics. This unique challenge is affecting the whole World, and while vaccination programs start to be deployed, in a few months the world will see the first Olympic Games' edition during a pandemic. The aim of this special paper was to consider the various challenges posed by the COVID pandemic and to provide information for coaching support staff to improve the preparation for Tokyo Olympics as well as consider the possible performance implications of this unique Olympic edition.

ZusammenfassungVerletzungen spielen eine gravierende Rolle im Hochleistungssport und treten sowohl im Training als auch im Wettbewerb auf. Handball ist ein Mannschaftssport mit hohen physischen Anforderungen und die Messung spezifischer Belastungen hat das Potenzial, Risikofaktoren für Verletzungen zu identifizieren. Nur wenige Studien haben dies im Handball während einer Weltmeisterschaft getan. Das Ziel dieser Studie ist die Erfassung von Schulterverletzungen, die während der 88 Spiele der Männer-Weltmeisterschaft 2015 auftraten, und positionsspezifische Unterschiede zu erörtern. Spieler aus 24 Nationalmannschaften wurden mithilfe eines Kamerasystems und einer speziellen Software (Prozone Handball V. 1.2, Prozone, Leeds, UK) analysiert. Insgesamt wurden 9 Schulterverletzungen erfasst. Für 3 dieser 9 Verletzungen konnte keine Fremdeinwirkung dokumentiert werden. Die Anzahl der Pässe und Würfe ist von der Spielposition abhängig und die höchste diesbezügliche Belastung weisen Rückraumspieler auf. Die beiden Rückraumspieler, die eine Non-Kontaktverletzung erlitten, weisen im Vergleich eine erhöhte Spielzeit und eine erhöhte Anzahl an Würfen auf. Es scheint, dass es einen Zusammenhang zwischen erhöhter Spielzeit und Verletzungen gibt. Um das Risiko einer Verletzung zu senken sollte sowohl die Belastung gemessen (während des Trainings und des Turniers) als auch eine gezielte Verletzungsprävention durchgeführt werden, um die Spieler auf die Anforderungen des Spiels/Turniers vorzubereiten.

Purpose: To quantify how many of the top 50 under-18 (U18) sprinters in the world managed to become top 50 ranked as adult competitors. The authors also described the career trajectory of athletes ranked in the top 50 during either U18 or senior category. Methods: A total of 4924 male and female athletes competing in sprint races and ranked in the International Association of Athletics Federations (now World Athletics) lists in any of the seasons between the 2000 and 2018 were included in the study. The athletes ranked in the top 50 positions of all-time lists during U18, senior, or both categories were analyzed. Results: Only 17% of the male and 21% of the female top 50 ranked U18 managed to become top 50 ranked senior athletes. The top 50 ranked senior athletes consistently produced yearly larger improvements during late adolescence and early adulthood compared with those who ranked in the top 50 at U18. Furthermore, top 50 ranked senior athletes reached their peak performance later compared with the top 50 ranked only in U18. Conclusions: This study confirms that early success in track and field is not a good predictor of success at senior level in sprinting events. The yearly performance improvements and their tracking provide the most suitable approach to identify athletes more likely to succeed as elite performers in adulthood. The authors hope that the results of this study can provide useful comparative data and reference criteria for talent-identification and -development programs.

This study aimed (a) to estimate the transition rate for top 50 ranked track and field jumpers, (b) to compare the performance progression of top 50 ranked senior jumpers (top50 senior) to those who failed to be top 50 ranked in the senior category despite being top 50 ranked in the under 18 category (only U18), and (c) to verify whether relative age effect may at least partially explain the differences in the two above-mentioned subgroups. The career performance trajectories of 5981 athletes (2837 females) competing in jump events from 2000 to 2019 were extracted from the World Athletics database. The all-time top 50 ranked athletes for each age from 16 years to senior category were identified. Performance progression characteristics were compared using linear mixed-effects model. Only 8% of males and 16% of females top 50 ranked at the age of 16 years managed to be included among the top50 senior. Only U18subgroup made the first appearance in the database (at 15-16 years) and reached the peak performance (at 20 years) earlier than top50 senior (17-18 and 26-27 years, respectively). The relative age effect was largely present in Only U18 but not in top50 senior subgroups. Most of the early-successful U18 world-class jumpers did not manage to maintain the same level of competitiveness in adulthood since they experienced a plateau in performance from 20 years of age. Conversely, top 50 ranked senior jumpers continued to produce consistent performance improvement up to 26-27 years of age.

Objectives To quantify the junior-to-senior successful transition rate in sprint swimming events in elite European performers. Design Retrospective analysis of publicly available competition data collected between 2004 and 2019. Methods The yearly performance of 6631 European swimmers (females = 41.8% of the sample) competing in 50 and 100 m freestyle, backstroke, breaststroke, and butterfly were included in the analysis. The junior-to-senior transition rate was determined as the number of elite junior athletes who maintained their elite status in adulthood. To investigate how the definition of elite may affect the calculation of the transition rate, we operationally defined elite athletes as those ranked in the all-time top 10, 25, 50, and 100 in their category. We also calculated the correlation between junior and senior performances. Results The average transition rates ranged, depending on the age of reference, from 10 to 26% in males and from 23 to 33% in females. The transition rate for the top 100 junior swimmers was greater than that for the top 10 swimmers. In general, swimmers who swam 50 m showed a slightly lower transition rate compared with those that swam 100 m. Depending on the age of reference, low-to-moderate correlations were observed between junior and senior peak performances. Conclusions Most elite junior athletes did not maintain the elite level in adulthood. Except for athletes in the last year of the junior category (18 years for males and 17 years for females), junior performances were poorly correlated with senior performances.

Context: The application of infrared thermography to assess the effects of athletic training is increasing. It is not known if changes in skin temperature (Tsk) as assessed by infrared thermography are affected by the training load or the muscle soreness experienced by the athlete. Purpose: To describe the variations in Tsk in body areas affected by running training and examine any relationships with subjective ratings of muscle soreness. The secondary aim was to assess the feasibility of using infrared thermography for assessing training load in 2 junior male middle-distance athletes. Methods: Data were collected over a 42-d observational period with Tsk of the quadriceps, knees, shins, lateral hamstrings, biceps femoris, and Achilles tendons, and the subjective ratings of muscle soreness were taken each morning prior to any training. All training load was quantified through heart rate, running speed, and distance covered. Changes in Tsk outside the typical error were identified. Relationships between Tsk and subjective ratings of muscle soreness were also examined. Results: Over the 42-d observational period, mean Tsk of the regions of interest was reported outside the typical error on day 31 and day 22 for athletes 1 and 2, respectively. These changes in Tsk did not follow trends similar to those of to training loadings. No significant relationships were observed between Tsk of any regions of interest and muscle soreness. Conclusions: Although Tsk changed outside the typical error throughout the 42-d observational period, these changes were not reflective of training load quantified through cardiovascular strain or subjective ratings of muscle soreness.

High volume power training (HVPT) involves high volumes of high-velocity resistance training, with the aim to improve repeated high-intensity efforts (RHIEs). Repeat power ability (RPA) is the ability to repeatedly produce maximal or near maximal efforts. Assessments of RPA using external loading may determine the ability to perform repeat RHIEs typical of many sports and, therefore, provide useful information on the effectiveness of training. (1) Identify the different HVPT protocols; (2) examine the acute responses and chronic adaptations to different HVPT protocols; (3) identify different lower body RPA assessment protocols and highlight similarities, differences and potential limitations between each protocol, and; (4) describe the reliability and validity of RPA assessments. An electronic search was performed using SPORTDiscus, PubMed, CINAHL and Embase for studies utilising HVPT protocols and assessments of RPA. Eligible studies included peer-reviewed journal articles published in English. Twenty studies met the inclusion criteria of the final review. Of the eight longitudinal studies, three were rated as fair and five were rated as poor methodological quality, respectively. In contrast, all 12 cross-sectional studies were considered to have a low risk of bias. Preliminary evidence suggests that HVPT can enhance RHIE, RPA, anaerobic capacity, anaerobic power and aerobic performance. HVPT generally consists of 2–3 sessions per week, utilising loads of 30–40% 1 repetition maximum (RM), for 3–5 sets of 10–20 repetitions, with inter-set rest periods of 2–3 min. RPA assessments can be valid and reliable and may provide useful information on an athlete’s ability to perform RHIE and the success of HVPT programmes. HVPT can be used to improve a number of physical qualities including RPA and RHIE; while a variety of RPA assessments provide valid and reliable information regarding the athlete’s ability to perform RHIEs. Considering the heterogeneity in the HVPT protocols currently used and the relatively low volume and quality of longitudinal publications in this area, further studies are needed to identify the effects of a variety of HVPT methods on RPA, RHIE and other performance outcomes and to identify the most valid and reliable RPA outcomes to use in such studies.

Although handball is a contact sport with a high risk of acute match injuries, their mechanisms have not yet been investigated. We aimed to describe the mechanisms of acute match injuries in elite male handball and evaluate referee performance in injury situations. Based on injury surveillance from the 24th Men's Handball World Championship 2015 in Qatar, injury situations and the referee decisions were identified on video footage. A total of 55 injury situations and 37 referee decisions were included for analysis. The injury situations were analyzed individually by five handball experts, followed by a consensus meeting. An expert referee panel performed individual blinded evaluation of the referee decisions, followed by an online consensus meeting. Injuries were evenly distributed among attackers (n = 29) and defenders (n = 26). The most frequent injury cause was contact trauma due to a tackle (n = 27). At the time of injury, attackers were most frequently performing a jump shot (n = 9), while defenders were completing a tackle (n = 10). Defenders most commonly tackled the throwing arm (n = 7) or toward the head/face region (n = 6) of injured attackers, while attackers most frequently hit injured defenders with the knee during jump shots (n = 5). Agreement between the referees and the expert panel was weak (kappa: 0.22, 95% CI 0.07 to 0.36), with substantially more lenient rule interpretation by the referees. Our results suggest that stricter refereeing and rule amendments should be considered to prevent acute match injuries in elite handball, especially in relation to tackling episodes when an attacker is performing a jump shot.

Goalkeepers have a very important role in handball. In coaching communities it is well recognized that goalkeepers' performances can predict team ranking in major tournaments. Despite this, few studies have been conducted on elite goalkeepers participating in World Championships. Therefore, the purpose of this study was to analyse goalkeepers' save performance during the 88 matches of the 2015 men's World Championships tournament. Goalkeepers from 24 national teams were analysed using a tracking camera system and bespoke software (Prozone Handball V.1.2, Prozone, Leeds, UK). The purpose of this study was to examine time-motion performance parameters and to evaluate the save rates for each goalkeeper. The mean total distance covered in a game by the goalkeepers was 1634±999 m. Goalkeepers spent most of the time walking or standing. The total amount of shots to the goal was 6893, with a mean save percentage of 30% (2088 saves). A significant relationship was identified between the goalkeepers' save statistics and the final team rankings. The save rate is important for teams to achieve a higher ranking, and therefore the selection and training of goalkeepers requires more than just assessing physical abilities. The throwing distribution and success/save rate during the Qatar 2015 Men Handball World Championships suggest strong and weak parts of the goal area, and coaches can use this information to adjust their training approaches for both goalkeepers and shooters.

© 2017 Human Kinetics, Inc. Monitoring the load placed on athletes in both training and competition has become a very hot topic in sport science. Both scientists and coaches routinely monitor training loads using multidisciplinary approaches, and the pursuit of the best methodologies to capture and interpret data has produced an exponential increase in empirical and applied research. Indeed, the field has developed with such speed in recent years that it has given rise to industries aimed at developing new and novel paradigms to allow us to precisely quantify the internal and external loads placed on athletes and to help protect them from injury and ill health. In February 2016, a conference on "Monitoring Athlete Training Loads-The Hows and the Whys" was convened in Doha, Qatar, which brought together experts from around the world to share their applied research and contemporary practices in this rapidly growing field and also to investigate where it may branch to in the future. This consensus statement brings together the key findings and recommendations from this conference in a shared conceptual framework for use by coaches, sport-science and-medicine staff, and other related professionals who have an interest in monitoring athlete training loads and serves to provide an outline on what athlete-load monitoring is and how it is being applied in research and practice, why load monitoring is important and what the underlying rationale and prospective goals of monitoring are, and where athlete-load monitoring is heading in the future.

Purpose:An extensive battery of physical tests is typically employed to evaluate athletic status and/or development, often resulting in a multitude of output variables. The authors aimed to identify independent physical predictors of elite skeleton start performance to overcome the general problem of practitioners employing multiple tests with little knowledge of their predictive utility.Methods:Multiple 2-d testing sessions were undertaken by 13 high-level skeleton athletes across a 24-wk training season and consisted of flexibility, dry-land push-track, sprint, countermovement-jump, and leg-press tests. To reduce the large number of output variables to independent factors, principal-component analysis (PCA) was conducted. The variable most strongly correlated to each component was entered into a stepwise multiple-regression analysis, and K-fold validation assessed model stability.Results:PCA revealed 3 components underlying the physical variables: sprint ability, lower-limb power, and strength–power characteristics. Three variables that represented these components (unresisted 15-m sprint time, 0-kg jump height, and leg-press force at peak power, respectively) significantly contributed (P < .01) to the prediction (R2 = .86, 1.52% standard error of estimate) of start performance (15-m sled velocity). Finally, the K-fold validation revealed the model to be stable (predicted vs actual R2 = .77; 1.97% standard error of estimate).Conclusions:Only 3 physical-test scores were needed to obtain a valid and stable prediction of skeleton start ability. This method of isolating independent physical variables underlying performance could improve the validity and efficiency of athlete monitoring, potentially benefitting sport scientists, coaches, and athletes alike.

Jones, TW, Shillabeer, BC, Ryu, JH, and Cardinale, M. Development in adolescent middle-distance athletes: a study of training loadings, physical qualities, and competition performance. J Strength Cond Res XX(X): 000-000, 2019-The purpose of this study was to examine changes in running performance and physical qualities related to middle-distance performance over a training season. The study also examined relationships between training loading and changes in physical qualities as assessed by laboratory and field measures. Relationships between laboratory and field measures were also analyzed. This was a 9-month observational study of 10 highly trained adolescent middle-distance athletes. Training intensity distribution was similar over the observational period, whereas accumulated and mean distance and training time and accumulated load varied monthly. Statistically significant (p 0.80) were observed for improvements in: body mass (5.6%), 600-m (4.6%), 1,200-m (8.7%), and 1,800-m (6.1%) time trial performance, critical speed (7.1%), V[Combining Dot Above]O2max (5.5%), running economy (10.1%), vertical stiffness (2.6%), reactive index (3.8%), and countermovement jump power output relative to body mass (7.9%). Improvements in 1,800 m TT performance were correlated with increases in V[Combining Dot Above]O2max (r = 0.810, p = 0.015) and critical speed (r = 0.918, p = 0.001). Increases in V[Combining Dot Above]O2max and critical speed were also correlated (r = 0.895, p = 0.003). Data presented here indicate that improvements in critical speed may be reflective of changes in aerobic capacity in adolescent middle-distance athletes.

Injuries are common in elite adolescent athletics, but few studies have addressed risk factors for injury. Growth and maturation are potential risk factors in this population; however, the current body of literature is both inconclusive and considered at high risk of bias. The aim of this study was therefore to examine whether growth rate, maturity status, and maturity tempo are associated with injury risk in an elite sports academy. Anthropometric, skeletal maturity and injury data collected prospectively over four seasons (117 athlete-seasons) were included in the analyses. Growth rate for stature was associated with greater risk of bone (incidence rate ratio (IRR): 1.5 per one standard deviation increase above the mean; 95% CI: 1.1-1.9) and growth plate injuries (IRR: 2.1; 1.5-3.1). Growth rate for leg length was associated with greater overall injury risk (IRR: 1.3; 1.0-1.7) as well as the risk of bone (IRR: 1.4; 1.0-1.9) and growth plate injuries (IRR: 2.1; 1.4-3.0). Athletes with greater skeletal maturity, expressed as skeletal age (IRR: 0.6 per year; 0.5-0.9) and percentage of predicted mature height (IRR: 0.8 per percent increase; 0.7-1.0), were less prone to growth plate injuries. Rate of change in skeletal age was associated with an increased risk of bone injuries (IRR: 1.5; 1.0-2.3). The results of this study suggest that rapid growth in stature and leg length, skeletal maturity status, and maturity tempo represent risk factors for certain injury types in adolescent athletics.

Athletes who merit the title ‘elite’ are rare and differ both quantitatively and qualitatively from athletes of lower qualifications. Serving and studying elite athletes may demand non-traditional approaches. Research involving elite athletes suffers because of the typical nomothetic requirements for large sample sizes and other statistical assumptions that do not apply to this population. Ideographic research uses single-athlete study designs, trend analyses, and statistical process control. Single-athlete designs seek to measure differences in repeated measurements under prescribed conditions, and trend analyses may permit systematic monitoring and prediction of future outcomes. Statistical process control uses control charting and other methods from management systems to assess and modify training processes in near real-time. These methods bring assessment and process control into the real world of elite athletics.

Background: There is a shortage of longitudinal surveys in highly trained adolescent table tennis athletes reporting typical changes in performance related, hematological, and biochemical parameters. Objectives: The purpose of the study was to: (1) examine yearly variations of performance related parameters, and (2) report the variability of selected hematological and biochemical markers utilized to ascertain health status, and training influences in a group of young Arab table tennis athletes. Methods: Data were collected from ten male adolescent players with a mean age of 14.2 ± 1.3 years and a mean table tennis training experience of 6 years. Physical and biochemical measures were carried out at three important time points throughout the training season: a baseline measure (PRE - September); a mid-season (transition) measure (MID - February); an end of season measure (END - May). Results: Performance related parameters tended to significantly improve over time (P = 0.05), with lowest values displayed during PRE-measure. Hematocrit (P = 0.05), serum testosterone (P = 0.01), mean cell volume (MCV) (P = 0.001) and reticulocytes (RET) (P = 0.017) significantly increased at the END training period compared to PRE. Moreover, 25(OH)D levels (P = 0.001) showed a drop during MID to then significantly increase at the END whilst sex hormone binding globulin (SHBG; P = 0.005) decreased at the END period compared to MID. Conclusions: In conclusion, based on our findings, changes in certain physical parameters and, hematological and biochemical markers, take place during the training period. Therefore, coaches, sports scientists and nutritionists should take into consideration these fluctuations and plan and alter their training programs accordingly.

Background: It has been established that injury incidence data and training load in table tennis is somewhat limited. Objectives: The purpose of this study was to analyze and report training load and injury incidence. This was established over a full season in highly trained youth table tennis athletes. We further aimed to establish what variables related to training load have a statistically significant effect on injury in youth table tennis. Methods: Data was collected from eight male adolescent table tennis players of Arabic origin. Training and game time were monitored continuously throughout each training session and match. Heart rate was measured throughout and then subsequently analyzed to quantify internal training load. Results: Players were subjected to an average of 1901 h 33 min ± 44 h 30 min of training time and 140 h 0 min ± 11 h 29 min of game time over the season. Overall injury incidence was 8.3 (95% CI: 4.6 - 12.0), time-loss injuries 4.4 (95% CI: 1.9 - 6.9) and growth conditions 2.0 (95% CI: 0.6 - 3.3) per 1000 hours. Internal training loads quantified via the Edwards training impulse equation were significantly different between training weeks (P = 0.001), with lowest values around competition periods (P < 0.05). For every extra auxiliary unit of relative training load per minute during training, a significant increase (P = 0.014) in injury occurrence was present. Conclusions: Most of the injuries occurred during the first quarter of the year (65%), when training loads were highest. In conclusion, the results of this preliminary study showed that training loads increase during a season until competition period, with relative training load per minute being linked to the likelihood of injuries. The rate of overuse injuries and growth-related conditions were higher than previously reported in adolescents in other racket sports.

Objectives The aim of this study was to describe and analyse the performance career trajectories for Italian athletes that participated in sprint, hurdles, discus throw, and shot-put athletics events. Design Retrospective study, data collected between 1994 and 2014. Methods A total of 5929 athletes (female: n = 2977, 50.2%) were included in the study. The age of entering competition and personal best performance was identified in the official competition records. Personal best performances were ranked in percentiles and top-level athletes were considered those in the highest 4% of the performance distribution. Results Overall, when controlling for the age of entering competition, top-level athletes reached their personal best later (i.e., around 23–25 years old) for all events compared to the rest of the athletes. Moreover, regression analysis showed that entering competitions later was linked to better performances during adulthood. Also, only 17%–26% [90% CI] of the top-level adult athletes were considered as such when they were 14–17 years old. Conclusions Together, these findings suggest that early sport success is not a strong predictor of top-level performance at senior level. Entering sport-specific competitions later and lengthening the sports career at beyond 23–25 years of age may be important factors to reach top-level performance in sprint and throwing events.

Cunniffe, B, Papageorgiou, M, O'Brien, B, Davies, NA, Grimble, GK, and Cardinale, M. Acute citrulline-malate supplementation and high-intensity cycling performance. J Strength Cond Res 30(9): 2638-2647, 2016-Dietary L-citrulline-malate (CM) consumption has been suggested to improve skeletal muscle metabolism and contractile efficiency, which would be expected to predispose exercising individuals to greater fatigue resistance. The purpose of this study was to examine the effects of CM supplementation on acid-base balance and high-intensity exercise performance. In a double-blind, placebo-controlled, crossover study, 10 well-trained males consumed either 12 g of CM (in 400 ml) or lemon sugar-free cordial (placebo [PL]) 60 minutes before completion of 2 exercise trials. Each trial consisted of subjects performing 10 (×15 seconds) maximal cycle sprints (with 30-second rest intervals) followed by 5 minutes recovery before completing a cycle time-to-exhaustion test (TTE) at 100% of individual peak power (PP). Significant increases in plasma concentrations of citrulline (8.8-fold), ornithine (3.9-fold), and glutamine (1.3-fold) were observed 60 minutes after supplementation in the CM trial only (p ≤ 0.05) and none of the subjects experienced gastrointestinal side-effects during testing. Significantly higher exercise heart rates were observed in CM condition (vs. PL) although no between trial differences in performance related variables (TTE: [120 ± 61 seconds CM vs. 113 ± 50 seconds PL]), PP or mean power, ([power fatigue index: 36 ± 16% CM vs. 28 ± 18% PL]), subjective rating of perceived exertion or measures of acid-base balance (pH, lactate, bicarbonate, base-excess) were observed (p > 0.05). This study demonstrated that acute supplementation of 12 g CM does not provide acute ergogenic benefits using the protocol implemented in this study in well-trained males.

Vibration exercise (VE) has been suggested as an effective method to improve strength and power capabilities. However, the underlying mechanisms in response to VE are still unclear. A pulley-like VE system, characterized by sinusoidal force applications has been developed and tested for proof of concept in a previous study. The aim of this study was to evaluate the effects of such force modulation on elbow flexors strength and compare it with conventional methods. Forty subjects were randomly divided into 4 groups of 10: the vibration group (VG), the no-vibration group (NVG), the dumbbell group (DG), and the control group (CG). Biceps curl exercises were used to train the elbow flexors 2 times a week for 8 weeks. Subjects in the VG were trained using a ramp-up baseline with superimposed 30 Hz sinusoidal vibration whereas the subjects in the NVG were trained using the same baseline but without vibration. Subjects in the DG were trained using dumbbells, and the subjects in the CG were not trained. The isometric break force (IBF) and 1 repetition maximum (1RM) of the subject's dominant arm were assessed before and after the 8-week training period. The VG achieved 1RM improvement (22.7%) larger than the NVG (10.8%) and comparable with the DG (22.3%). Differences in IBF gains following the training period among the training groups were found to be not significant. Our results support the inclusion of the proposed VE in strength training programs aimed at improving dynamic strength on the elbow flexors.

Although the role of vitamin D in calcium and bone metabolism is well documented, there is little clarity regarding the implications of low vitamin D status for inflammation, endothelial function, and antioxidant status in adolescent athletes. A prospective cohort study was conducted, and 44 male adolescent athletes, training at a sports academy in the Middle East, were assigned to either the intervention group (VitDs), consisting of vitamin D deficient athletes [twenty-five hydroxyvitamin D (25(OH)D) 30 ng/ml ; n = 22]. Vitamin D status, inflammatory cytokines, endothelium-related variables, and antioxidant enzymes were measured twice during a nine-week training period. At the baseline, the athletes in the VitDs group had significantly lower concentrations of 25(OH)D, vascular endothelial growth factor (VEGF), and glutathione peroxidase (GPx), and higher levels of parathyroid hormone (PTH), interleukin-6 (IL-6), interleukin-1 receptor antagonist (IL-1ra), and nitrite (NO2) (p < 0.05), in comparison to the athletes in the sufficient group. After vitamin D supplementation for the VitDs group, the two cohorts differed considerably in vitamin D binding protein (VDBP) and PTH concentrations (p < 0.05). Our data suggest that the low levels of vitamin D possibly induced alterations in the investigated biochemical parameters of athletes in the VitDs group at the beginning of the monitoring period. Furthermore, while the vitamin D supplementation was effective in increasing 25(OH)D status, it may have concurrently positively influenced variables that are related to inflammation, endothelial function, and enzymatic antioxidants.

BACKGROUND: The aim of study was to examine the acute physiological responses and their relationship with physiological characteristics of preadolescent male handball players. METHODS: Laboratory testing included anthropometric measurements and spiroergometry. Time motion analysis data were obtained through recording of player’s game activities and later analyzed with a bespoke software package developed with Matlab. Heart Rate data was recorded with chest straps. Blood samples were collected at 5 predetermined time points over the course of 2 matches. RESULTS: T-test and Pearson product moment correlation coefficient was used to examine the differences and the relationship between variables collected in the study. Time motion analysis did not show significant differences between the total distance covered by players in the first (2220.50±162.85 meters) and in the second (2131.42±239.80 meters ; Cohen’s d=0.43) half of the match ; however the effect size was small to moderate. A significant moderate relationship between blood lactate at the end of the second half and the difference in the distance covered between 2nd and 1st half (r=0.50, P

This study evaluated the effect of game venue and starting status on precompetitive psychophysiological measures in elite rugby union. Saliva samples were taken from players (starting XV, n = 15, and nonstarters, n = 9) on a control day and 90 min before 4 games played consecutively at home and away venues against local rivals and league leaders. Precompetition psychological states were assessed using the Competitive State Anxiety Inventory−2. The squad recorded 2 wins (home) and 2 losses (away) over the study period. Calculated effect sizes (ESs) showed higher pregame cortisol- (C) and testosterone- (T) difference values before all games than on a baseline control day (ES 0.7−1.5). Similar findings were observed for cognitive and somatic anxiety. Small between-venues C differences were observed in starting XV players (ES 0.2−0.25). Conversely, lower home T- (ES 0.95) and higher away C- (ES 0.6) difference values were observed in nonstarters. Lower T-difference values were apparent in nonstarters (vs starting XV) before home games, providing evidence of a between-groups effect (ES 0.92). Findings show an anticipatory rise in psychophysiological variables before competition. Knowledge of starting status appears a moderating factor in the magnitude of player endocrine response between home and away games.

Little data exists on drinking behavior, sweat loss, and exercise intensity across a competitive handball tournament in elite female athletes. Heart rate (HR), fluid balance and sweat electrolyte content were assessed on 17 international players across a 6-day tournament involving 5 games and 2 training sessions played indoors (23 ± 2 °C, 30 ± 2% relative humidity). Active play (effective) mean HR was 155 ± 14 bpm (80 ± 7.5% HRmax) with the majority of time (64%) spent exercising at intensities >80% HRmax. Mean (SD) sweat rates during games were 1.02 ± 0.07 L · h-1 and on 56% of occasions fluid intake matched or exceeded sweat loss. A significant relationship was observed between estimated sweat loss and fluid intake during exercise (r2 = .121, p = .001). Mean sweat sodium concentration was 38 ± 10 mmol · L-1, with significant associations observed between player sweat rates and time spent exercising at intensities >90% HRmax (r2 = .181, p = .001). Fluid and electrolyte loss appear to be work rate dependent in elite female handball players, whom appear well capable of replacing fluids lost within a tournament environment. Due to large between-athlete variations, a targeted approach may be warranted for certain players only.

Purpose:Running performance is influenced by the interaction of biomechanical and physiological factors. Miniaturized accelerometers worn by athletes can be used to quantify mechanical aspects of running and as a noninvasive tool to assess training status and progression. The aim of this study was to define and validate a method to assess running regularity and allow the estimation of an individual’s oxygen uptake (V̇O2) and/or blood lactate—[La]b—based on data collected with accelerometers and heart rate.Methods:Male adolescent endurance athletes completed an incremental submaximal aerobic stage test where V̇O2 and [La]b were measured. The test was terminated when [La]b concentration at the end of the stage exceeded 4 mmol/L. Two wireless triaxial accelerometers were placed on participants’ right shank and lower back throughout the test. The root mean square (RMS) and sample entropy (SampEn) were calculated for the vertical, mediolateral, and anteroposterior components of acceleration.Results:There were significant positive correlations of acceleration and entropy variables with [La]b and V̇O2, with moderate to high coefficients (r = .43–.87). RMS of the shank acceleration was the most highly related with both physiological variables. When the accelerometer was attached on the trunk, SampEn of the vertical acceleration had the strongest relationship with V̇O2 (r = .76, P < .01).Conclusions:The described method analyzing running complexity may allow an assessment of gait variability, which noninvasively tracks V̇O2 and/or [La]b, allowing monitoring of fatigue or training readiness for trained adolescent individuals.

Refereed/Peer-reviewed

Purpose:To examine the training and concomitant changes in laboratory- and field-test performance of highly trained endurance runners.Methods:Fourteen highly trained male endurance runners (mean ± SD maximal oxygen uptake [VO2max] 69.8 ± 6.3 mL · kg−1 · min−1) completed this 1-y training study commencing in April. During the study the runners undertook 5 laboratory tests of VO2max, lactate threshold (LT), and running economy and 9 field tests to determine critical speed (CS) and the modeled maximum distance performed above CS (D′). The data for different periods of the year were compared using repeated-measures ANOVA. The influence of training on laboratory- and field-test changes was analyzed by multiple regression.Results:Total training distance varied during the year and was lower in May–July (333 ± 206 km, P = .01) and July–August (339 ± 206 km, P = .02) than in the subsequent January–February period (474 ± 188 km). VO2max increased from the April baseline (4.7 ± 0.4 L/min) in October and January periods (5.0 ± 0.4 L/min, P ≤ .01). Other laboratory measures did not change. Runners’ CS was lowest in August (4.90 ± 0.32 m/s) and highest in February (4.99 ± 0.30 m/s, P = .02). Total training distance and the percentage of training time spent above LT velocity explained 33% of the variation in CS.Conclusion:Highly trained endurance runners achieve small but significant changes in VO2max and CS in a year. Increases in training distance and time above LT velocity were related to increases in CS.

AB Purpose: Previous work identified an asymmetry in tissue desaturation changes in the left and right quadriceps muscles during on-ice skating at maximal speed in males. The effect of changing race distance on the magnitude of desaturation or leg asymmetry is unknown. Methods: Six elite male skaters (age = 23 +/- 1.8 yr, height = 1.8 +/- 0.1 m, mass = 80.1 +/- 5.7 kg, midthigh skinfold thickness = 7 +/- 2 mm) and four elite female skaters (age = 21 +/- 4 yr, height = 1.6 +/- 0.1 m, mass = 65.2 +/- 4.3 kg, midthigh skinfold thickness = 10 +/- 1 mm) were studied. Subjects completed time trials over three race distances. Blood lactate concentration and O2 uptake measurements were combined with near-infrared spectroscopy measures of muscle oxygenation (TSI) and blood volume (tHb) in the right and left vastus lateralis. Results: Neither race distance nor gender had a significant effect on the magnitude of maximal muscle desaturation ([DELTA]TSImax). Pattern of local changes in tHb during individual laps was dependent upon subtle differences in skating technique used for the different race distances. Linear regression analysis revealed asymmetry between the right and left leg desaturation in males during the final stages of each race distance, but not in females. At all race distances, local muscle desaturation reached maximal values much more quickly than global V[spacing dot above]O2peak. Conclusion: The use of wearable near-infrared spectroscopy devices enabled measurement of muscle oxygenation during competitive race simulation, thus providing unique insight into the effects of velocity and technique changes on local muscle oxygenation. This may have implications for training and race pacing in speed skating

The need to quantify aspects of training to improve training prescription has been the holy grail of sport scientists and coaches for many years. Recently, there has been an increase in scientific interest, possibly due to technological advancements and better equipment to quantify training activities. Over the last few years there has been an increase in the number of studies assessing training load in various athletic cohorts with a bias toward subjective reports and/or quantifications of external load. There is an evident lack of extensive longitudinal studies employing objective internal-load measurements, possibly due to the cost-effectiveness and invasiveness of measures necessary to quantify objective internal loads. Advances in technology might help in developing better wearable tools able to ease the difficulties and costs associated with conducting longitudinal observational studies in athletic cohorts and possibly provide better information on the biological implications of specific external-load patterns. Considering the recent technological developments for monitoring training load and the extensive use of various tools for research and applied work, the aim of this work was to review applications, challenges, and opportunities of various wearable technologies.

Cunniffe, B, Ellison, M, Loosemore, M, and Cardinale, M. Warm-up practices in elite boxing athletes: Iimpact on power output. J Strength Cond Res 31(1): 95-105, 2017-This study evaluated the performance impact of routine warm-up strategies in elite Olympic amateur boxing athletes and physiological implications of the time gap (GAP) between warm-up and boxing activity. Six male boxers were assessed while performing standardized prefight warm-up routines. Core and skin temperature measurements (Tcore and Tskin), heart rate, and upper- and lower-body power output (PO) were assessed before and after warm-up, during a 25-minutes GAP and after 3 × 2 minutes rounds of sparring. Reflected temperature (Tc) was also determined using high-resolution thermal images at fixed time-points to explore avenues for heat loss. Despite individual differences in warm-up duration (range 7.4-18.5 minutes), increases in Tcore and Tskin occurred (p ≤ 0.05). Corresponding increases (4.8%; p ≤ 0.05) in countermovement jump (CMJ) height and upward-rightward shifts in upper-body force-velocity and power-velocity curves were observed. Athletes remained inactive during the 25-minutes GAP with a gradual and significant increase in Tc occurring by the end of GAP suggesting the likelihood of heat loss. Decreases in CMJ height and upper-body PO were observed after 15 minutes and 25 minutes GAP (p ≤ 0.05). By the end of GAP period, all performance variables had returned to pre-warm-up values. Results suggest routine warm-ups undertaken by elite boxers have acute effects on power-generating capacity. Gradual decreases in performance variables are evident with inactivity and seem related to alterations in body temperature. Considering the constraints of major competitions and time spent in air conditioned holding areas before fights, practitioners should be aware of the potential of nullifying the warm-up effects.

Objectives: Assess current practice and attitudes towards recovery in adolescent athletes.Design: Questionnaires were administered either via print or online questionnaire.Participants: Athletes and coaches from within Asia were surveyed (n = 112 & 53), with a comparative sample in the UK (n = 53 & 8).Main Outcome Measures: The approaches and attitudes to recovery in both training and competition.Results: Adolescent athletes perceive a variety of recovery modalities as important, though prioritise active recovery, nutrition and sleep. Attitudes towards recovery differed between athletes in Asia and the UK with respect to the perceived benefits of: sleep (96% believe in it in the UK v 69% in Asia, p < 0.01); nutrition (92 v 58%, p < 0.01); and active recovery (70 v 52%, p = 0.03). The number of recovery techniques used with Asian athletes was higher after training (p = 0.009) and competition (p < 0.01). Asian athletes rely more on ‘feel’ to justify interventions.Conclusions: There was a major disconnect amongst athletes’ belief in particular strategies and their behaviours. The results of this study show the need for educating coaches and athletes.

MISCHI, M., and M. CARDINALE. The Effects of a 28-Hz Vibration on Arm Muscle Activity during Isometric Exercise. Med. Sci. Sports Exerc., Vol. 41, No. 3, pp. 00–00, 2009. Purpose: The aim of this study was to evaluate activation and coactivation of biceps and triceps muscles during isometric exercise performed with and without superimposing a vibration stimulation. Methods: Twelve healthy volunteers (age = 22.7 T 2.6 yr) participated in this study. The subjects performed five trials of isometric elbow flexion and five trials of elbow extension with increasing levels of force in two conditions: vibration (V) and normal loading (C). V stimulation was characterized by a frequency of 28 Hz. Surface EMG activity of biceps and triceps muscles was simultaneously measured by bipolar surface electromyography and assessed by the estimation of the root mean square (RMS) of the electrical recordings over a fixed 5-s interval. Frequency analysis was adopted to estimate the RMS related to muscle activation and to exclude the harmonics generated by movement artifacts due to V. Results: The analysis of the recordings revealed a significant EMGRMS increase when V was applied. On average, the EMGRMS of biceps and triceps during elbow flexion was, respectively, 26.1% (P G 0.05) and 18.2% (P = 0.15) higher than C. During elbow extension, the EMGRMS of biceps and triceps was 77.2% and 45.2% (P G 0.05) higher than C, respectively. The coactivation was assessed as the ratio between the activation of antagonist and agonist muscles during arm flexion and extension tasks. The results revealed an increase of coactivation during V exercise, especially for lighter loads. Conclusion: This study shows that V exercise at 28 Hz produces an increase of the activation and the coactivation of biceps and triceps. This exercise modality seems

Whole-body vibration (WBV) has been recently suggested as an alternative form of exercise. In this study, the acute effects of a single session of WBV exercise on anabolic hormones in aged individuals were analysed.A randomised cross-over trial design was used.Geriatrics Department, Woodend Hospital.20 individuals (9 men and 11 women; median age 70 years (range 66 to 85 years) volunteered in the experiment. Interventions Isometric squat on a platform with vibration or no vibration (control) conditions.Plasma cortisol, testosterone, growth hormone (GH) and insulin-like growth factor 1 (IGF-1) were measured before, immediately after, and 1 and 2 h after the interventions.A significant difference between treatments (p0.001) and a time x treatment interaction (p0.05) was found in IGF-1 levels. Cortisol levels were shown not to be significantly different between treatments (p = 0.43), but a difference over time (p0.001) and a time6 treatment interaction (p0.05) were identified. No significant differences were identified in GH and testosterone levels.As shown by the results of the study, 5 min of WBV exercise characterised by static squat with a frequency of 30 Hz can be performed by older individuals without apparent signs of stress and/or fatigue. Furthermore, WBV produced an acute increase in the circulating levels IGF-1 and cortisol greater than that observed following the same exercise protocol conducted without vibration.

Recovery and regeneration modalities have been developed empirically over the years to help and support training programmes aimed at maximizing athletic performance. Professional athletes undergo numerous training sessions, characterized by differing modalities of varying volumes and intensities, with the aim of physiological adaptation leading to improved performance. Scientific support to athletes focuses on improving the chances of a training programme producing the largest adaptive response. In competition it is mainly targeted at maximizing the chances of optimal performance and recovery when high performance levels are required repeatedly in quick succession (e.g. heats/finals). In recent years, a lot of emphasis has been put on recovery modalities. In particular, emphasis has been placed on the need to reduce the delayed onset of muscle soreness (DOMS) typically evident following training and competitive activities inducing a certain degree of muscle damage. One of the most used recovery modalities consists of cold-water immersion and/or ice/cold applications to muscles affected by DOMS. While the scientific literature has provided a rationale for such modalities to reduce pain in athletes and recreationally active adults, it is doubtful if this rationale is appropriate to aid training with adolescent athletes. In particular, since these methods have been suggested to potentially impair the muscle remodeling process leading to muscle hypertrophy. While this debate is still active in the literature, many coaches adopt such practices in youth populations, simply transferring what they see in elite sportspeople directly; without questioning the rationale, safety or effectiveness as well as the potential for such activity to reduce the adaptive potential of skeletal muscle remodeling in adolescent athletes. The aim of this review was to assess the current knowledge base on the use of ice/cold applications for recovery purposes in adolescent athletes in order to provide useful guidelines for sports scientists, medical practitioners, physiotherapists and coaches working with such populations as well as developing research questions for further research activities in this area. Based on the current evidence, it seems clear that evidence for acute benefits of such interventions are scarce and more work is needed to ascertain the physiological implications on a pre or peri-pubertal population. Electronic supplementary material The online version of this article (doi:10.1186/s13728-015-0035-8) contains supplementary material, which is available to authorized users.

Objectives To analyse the acute effects of spinal manipulation on neuromuscular function in asymptomatic individuals. Design Randomised controlled, cross-over trial. Settings Spinal manipulation (SM) is used as therapeutic modality for various neuromuscular disorders and also in sport with asymptomatic individuals to improve range of motion and/or facilitate motor control. Experimental evidence of its effectiveness is lacking. Participants 27 asymptomatic participants (15 males and 12 females) [age (mean ± standard deviation) 24 ± 3 years] were exposed to three separate treatments in random order: 1) Spinal Manipulation of the lumbar spine (MAN); 2) Stretching of the Lumbar spine (STR); 3) sham manipulation (SHA). Main outcome measures Before (PRE), after (POST) and 15 min after (15_MIN) each treatment, the participants were asked to perform three tasks always in the same order: 1) force fluctuation task; 2) Modified Sorensen's test; 3) sit and reach. Surface EMG was recorded from Gastrocnemius medialis and Erector Spinae muscles using linear arrays during task 1 and 2. Results MAN was not shown to determine improvements superior to other treatments in the control of force output and sEMG parameters. Conclusions Studies with larger populations are needed in order to ascertain the effectiveness of SM on neuromuscular function.

The primary objective of this study was to analyze the relationship between testosterone levels and vertical jumping performance in elite men and women athletes. The secondary objective was to verify whether testosterone levels and vertical jumping performance were different in men and women athletes and if those measurements were different between different athletic groups. Seventy (22 women and 48 men) elite athletes in track and field (sprinters), handball, volleyball, and soccer competing at national and international levels participated in the study. After 10 hours of fasting and 1 day of rest, blood samples were drawn from the antecubital vein for determining testosterone levels. Vertical jumping tests consisted of countermovement jumps conducted on a resistive platform connected to a digital timer. Resting testosterone levels in women were 9.5% of those of the men (respectively 0.62 +/- 0.06 ng.ml(-1) and 6.49 +/- 0.37 ng.ml(-1); p < 0.001). Countermovement jump performance was significantly different between women and men athletes, with women's jumping ability 86.3% of that of men (p < 0.001). A significant positive relationship was identified between testosterone levels and vertical jump performance when all data where considered (r = 0.61, p < 0.001, n = 70).

Whole body vibration has been recently proposed as an exercise intervention because of its potential for increasing force generating capacity in the lower limbs. Its recent popularity is due to the combined effects on the neuromuscular and neuroendocrine systems. Preliminary results seem to recommend vibration exercise as a therapeutic approach for sarcopenia and possibly osteoporosis. This review analyses state of the art whole body vibration exercise techniques, suggesting reasons why vibration may be an effective stimulus for human muscles and providing the rationale for future studies.

Background Handball is a contact sport with a high prevalence of acute injuries. Injuries often occur during high-speed movements involving several players, making it difficult to describe the exact mechanism of injury. Objective Describe the mechanisms of injury in elite male handball. Design Prospective video analysis. Setting During the men´s handball world championship 2015, 132 injuries were reported through on-site injury surveillance by team medical staff. Based on the injury reports, two operators accessed the videos of each game and identified the specific injury situations using video analysis software (ProzoneHANDBALL v.1.0.0.14, ProzoneSports, Leeds, UK). Video analysis A total of 97 injury videos were identified; 42 were excluded, as the injury situation was not visible. Five handball experts performed an individual analysis of the 55 included videos based on a specific form developed to describe the injury situations and causes, followed by a consensus meeting. Main Outcome Measurements The form included variables related to the playing situation, landing situation, action of attacker and defender at time of injury and localization of tackle/hit. Results The most common injury location was the head and face (n=17, 31%), followed by the ankle (n=6, 11%). The most frequent injury cause was opponent contact (n=27, 49%), followed by landing trauma subsequent to opponent contact (n=8, 15%). The injuries were equally distributed between attackers (n=29, 53%) and defenders (n=26, 47%), but time-loss injuries (49%) were more common among attackers (68%). The most frequent playing action performed by injured attackers was a jump shot (n=9, 31%); tackles were most often to their throwing arm (n=7, 30%). Conclusions Acute injuries in elite male handball are equally distributed between attackers and defenders. However, attackers sustain more severe injuries. The most frequent injury causes are direct opponent contact and landing trauma after opponent contact.

The aim of this study was to examine the magnitude and the origin of neuromuscular fatigue induced by half-squat static whole-body vibration (WBV) exercise, and to compare it to a non-WBV condition. Nine healthy volunteers completed two fatiguing protocols (WBV and non-WBV, randomly presented) consisting of five 1-min bouts of static half-squat exercise with a load corresponding to 50 % of their individual body mass. Neuromuscular fatigue of knee and ankle muscles was investigated before and immediately after each fatiguing protocol. The main outcomes were maximal voluntary contraction (MVC) torque, voluntary activation, and doublet peak torque. Knee extensor MVC torque decreased significantly (P

The aims of this study were to assess the behavior of a vibrating platform under different conditions and to compare the effects of an 8-week periodized training program with whole-body vibration (WBV) alone or in combination with conventional strength training (ST). Vibrating frequencies, displacements, and peak accelerations were tested through a piezoelectric accelerometer under different conditions of load and subjects' position. Eighteen national-level female athletes were assigned to 1 of 3 different groups performing WBV, conventional ST, or a combination of the 2 (WBV + ST). Isometric maximal voluntary contraction, dynamic maximal concentric force, and vertical jump tests were performed before and after the conditioning program. Vibrating displacements and maximum accelerations measured on the device were not always consistent with their expected values calculated from the display and manufacturers' information (sinusoidal waveforms). The WBV alone or in combination with low-intensity resistance exercise did not seem to induce significant enhancements in force and power when compared with ST. It appears that WBV cannot substitute parts of ST loading in a cohort of young female athletes. However, vibration effects might be limited by the behavior of the commercial platforms as the one used in the study. More studies are needed to analyze the performances of devices and the effectiveness of protocols.

PURPOSE: It has been suggested that, because of the low sitting position in short-track speed skating, muscle blood flow is restricted, leading to decreases in tissue oxygenation. Therefore, wearable wireless-enabled near-infrared spectroscopy (NIRS) technology was used to monitor changes in quadriceps muscle blood volume and oxygenation during a 500-m race simulation in short-track speed skaters. METHODS: Six elite skaters, all of Olympic standard (age = 23 ± 1.8 yr, height = 1.8 ± 0.1 m, mass = 80.1 ± 5.7 kg, midthigh skinfold thickness = 7 ± 2 mm), were studied. Subjects completed a 500-m race simulation time trial (TT). Whole-body oxygen consumption was simultaneously measured with muscle oxygenation in right and left vastus lateralis as measured by NIRS. RESULTS: Mean time for race completion was 44.8 ± 0.4 s. VO 2 peaked 20 s into the race. In contrast, muscle tissue oxygen saturation (TSI%) decreased and plateaued after 8 s. Linear regression analysis showed that right leg TSI% remained constant throughout the rest of the TT (slope value = 0.01), whereas left leg TSI% increased steadily (slope value = 0.16), leading to a significant asymmetry (P < 0.05) in the final lap. Total muscle blood volume decreased equally in both legs at the start of the simulation. However, during subsequent laps, there was a strong asymmetry during cornering; when skaters traveled solely on the right leg, there was a decrease in its muscle blood volume, whereas an increase was seen in the left leg. CONCLUSIONS: NIRS was shown to be a viable tool for wireless monitoring of muscle oxygenation. The asymmetry in muscle desaturation observed on the two legs in short-track speed skating has implications for training and performance. © 2012 by the American College of Sports Medicine.

The aim of this review is to highlight two emerging concepts for the elite athlete using the resistance-training model: (i) the short-term effects of testosterone (T) and cortisol (C) on the neuromuscular system; and (ii) the dose-response training role of these endogenous hormones. Exogenous evidence confirms that T and C can regulate long-term changes in muscle growth and performance, especially with resistance training. This evidence also confirms that changes in T or C concentrations can moderate or support neuromuscular performance through various short-term mechanisms (e.g. second messengers, lipid/protein pathways, neuronal activity, behaviour, cognition, motor-system function, muscle properties and energy metabolism). The possibility of dual T and C effects on the neuromuscular system offers a new paradigm for understanding resistance-training performance and adaptations. Endogenous evidence supports the short-term T and C effects on human performance. Several factors (e.g. workout design, nutrition, genetics, training status and type) can acutely modify T and/or C concentrations and thereby potentially influence resistance-training performance and the adaptive outcomes. This novel short-term pathway appears to be more prominent in athletes (vs non-athletes), possibly due to the training of the neuromuscular and endocrine systems. However, the exact contribution of these endogenous hormones to the training process is still unclear. Research also confirms a dose-response training role for basal changes in endogenous T and C, again, especially for elite athletes. Although full proof within the physiological range is lacking, this athlete model reconciles a proposed permissive role for endogenous hormones in untrained individuals. It is also clear that the steroid receptors (cell bound) mediate target tissue effects by adapting to exercise and training, but the response patterns of the membrane-bound receptors remain highly speculative. This information provides a new perspective for examining, interpreting and utilizing T and C within the elite sporting environment. For example, individual hormonal data may be used to better prescribe resistance exercise and training programmes or to assess the trainability of elite athletes. Possible strategies for acutely modifying the hormonal milieu and, thereafter, the performance/training outcomes were also identified (see above). The limitations and challenges associated with the analysis and interpretation of hormonal research in sport (e.g. procedural issues, analytical methods, research design) were another discussion point. Finally, this review highlights the need for more experimental research on humans, in particular athletes, to specifically address the concept of dual steroid effects on the neuromuscular system.

Purpose: The aim of this study was to investigate the effects of different whole-body vibration (WBV) frequencies on oxygenation of vastus lateralis (VL) and gastrocnemius medialis (GM) muscles during static squatting in sedentary and physically active healthy males. Methods: Twenty volunteers (age: 24.6 ± 2.9 yr; body mass: 80.6 ± 11.8 kg; height: 178.1 ± 7.6 cm) participated in this study. Ten subjects were sedentary individuals and 10 were athletes practicing different sports. All subjects completed four trials (control, and 30-, 40-, and 50-Hz WBV) in a randomized controlled crossover design. The trials consisted of static squatting on a vibrating platform for a total duration of 110 s. Muscle-oxygenation status was recorded with near-infrared spectroscopy. Results: The data analysis revealed no significant treatment-by-time interactions in tissue-oxygenation index (TOI) or ? total hemoglobin volume (tHb) in VL and GM muscles. A significant main effect of time in TOI of both VL and GM muscles was identified (P < 0.001). VL TOI significantly decreased by 2.8% at 90 s in the control condition and by 3.3% at 110 s in the 30-Hz condition; VL TOI significantly increased by 2.1 and 3.0% at 30 s in the 40- and 50-Hz conditions, respectively. GM TOI significantly decreased by 3.2% at 60 s, by 4.1% at 90 s, and by 4.3% at 110 s in the control condition, and by 5.5% at 110 s in the 30-Hz condition. Conclusion: This study showed that WBV exercise with frequencies of 30, 40, and 50 Hz and small amplitudes does not affect muscle oxygenation of VL and GM muscles to a higher degree than a nonvibration condition.

Excess protein intake can adversely affect the bone via an increase in calcium excretion, while suitable mechanical loading promotes osteogenesis. We therefore investigated whether vibration exposure could alleviate the bone mineral losses associated with a metabolic acidosis. Ten healthy individuals aged 22 - 29 years (median = 25) underwent three 5-day study periods while monitoring their dietary intake. The study consisted of recording the participants' usual dietary intake for 5 consecutive days. Participants were then randomly divided into two groups, one of which received a protein supplement (2 g x kg(-1) body mass x day(-1); n = 5) and the other whole-body low-magnitude (3.5 g), low-frequency (30 Hz) mechanical vibration (WBV) delivered through a specially designed vibrating plate for 10 min each day (n = 5). Finally, for the third treatment period, all participants consumed the protein supplement added to their normal diet and were exposed to WBV exercise for 10 min per day. Daily urine samples were collected throughout the experimental periods to determine the excretion of calcium, phosphate, titratable acid, urea, and C-telopeptide. As expected, when the participants underwent the high protein intake, there was an increase in urinary excretion rates of calcium (P0.001), phosphate (P0.003), urea (P0.001), titratable acid (P0.001), and C-telopeptide (P0.05) compared with baseline values. However, high protein intake coupled with vibration stimulation resulted in a significant reduction in urinary calcium (P = 0.006), phosphate excretion (P = 0.021), and C-telopeptide (P0.05) compared with protein intake alone, but did not affect titratable acid and urea output. The participants showed no effect of WBV exercise alone on urinary excretion of calcium, phosphate, urea, titratable acid, or C-telopeptide. The results indicate that vibration stimulation can moderate the increase in bone resorption and reduction in bone formation caused by a metabolic acidosis.