Yo-Yo Intermittent Recovery Level Research Articles

Test-Retest Reliability of the Yo-Yo Test: A Systematic Review.

The Yo-Yo test is widely used both in the practical and research contexts; however, its true test-retest reliability remains unclear. The present systematic review aims to identify studies that have examined the test-retest reliability of the Yo-Yo test and summarize their results. A search of ten databases was performed to find studies that have investigated test-retest reliability of any variant of the Yo-Yo test. The COSMIN checklist was employed to assess the methodological quality of the included studies. Nineteen studies of excellent or moderate methodological quality were included. When considering all variants of the Yo-Yo test, the included studies reported intra-class correlation coefficients for test-retest reliability ranging from 0.78 to 0.98 where 62% of all intra-class correlation coefficients were higher than 0.90, while 97% of intra-class correlation coefficients were higher than 0.80. The coefficients of variation ranged from 3.7 to 19.0%. Regardless of the variant of the test, the participants' familiarization with the test, and previous sport experience, the intra-class correlation coefficients generally seem high (≥ 0.90) and coefficients of variation low (< 10%). The results of this review indicate that the Yo-Yo test (in all its variants) generally has good-to-excellent test-retest reliability. The evidence concerning reliability arises from 19 included studies that were of moderate or high methodological quality. Considering that most of the included studies examined the Yo-Yo intermittent recovery level 1 test while including Association Football players, more reliability studies examining Yo-Yo intermittent recovery level 2 test and Yo-Yo intermittent endurance level 1 and level 2 tests, and in the context of sports other than Association Football as well as in non-athletic populations, are required. Finally, future studies should explicitly state the type of intra-class correlation coefficient used for the reliability data analysis to allow for better between-study comparisons.

Dose-Response Relationship Between Internal Training Load and Changes in Performance During the Preseason in Youth Soccer Players.

Figueiredo, DH, Figueiredo, DH, Moreira, A, Gonçalves, HR, and Dourado, AC. Dose-response relationship between internal training load and changes in performance during the preseason in youth soccer players. J Strength Cond Res 35(8): 2294-2301, 2021-The aim of this study was to describe training intensity distribution based on the session rating of perceived exertion (sRPE) and heart rate (HR) methods and examine the dose-response relation between internal training load (ITL) and change in performance of 16 youth soccer players (mean ± SD age: 18.75 ± 0.68 years, height: 175.3 ± 5.5 cm, body mass: 68.7 ± 6.5 kg, and body fat: 10.7 ± 1.2%) belonging to a Brazilian first division team during a 3-week preseason. The sRPE and HR data were registered daily to calculate the ITL and the training intensity distribution, in 3 intensity zones (low, moderate, and high). The Yo-yo Intermittent Recovery Level 1 (Yo-yo IR1) was evaluated before and after experimental period. The total time spent in the low-intensity zone (HR method) was greater (p < 0.01) compared with the moderate- and high-intensity zones. No difference was observed between training intensity zones determined by the sRPE method (p > 0.05). Negative correlations were observed between weekly mean sRPE-TL (r = -0.69), Edward's-TL (r = -0.50), and change in Yo-yo IR1. Linear regression indicated that weekly mean sRPE-TL (F1;14 = 13.3; p < 0.01) and Edward's-TL (F1;14 = 4.8; p < 0.05) predicted 48.7 and 25.5% of the variance in performance change, respectively. Stepwise linear regression revealed that these 2-predictor variables (F2;13 = 18.9; p < 0.001) explained 74.5% of the variance in performance change. The results suggest that the sRPE and HR methods cannot be used interchangeably to determine training intensity distribution. Moreover, sRPE-TL seems to be more effective than the HR-based TL method to predict changes in performance in youth soccer players.

Determinants of drop-out in youth basketball: an interdisciplinary approach

ABSTRACTUsing an interdisciplinary approach, we examined the baseline variation in biological maturity status, training experience, body size, functional capacities (Line Drill test and Yo-Yo Intermittent Recovery level 1 test) and motivation for achievement, competitiveness and deliberate practice of youth basketball players according to their participation status in the sport two years after assessment. Fifty-seven players were considered (10.5 to 15.5 years). Two years later we ascertained whether players discontinued participation (dropout), or remained playing engaged within a structured basketball training program. Taller adolescent players were more likely to be selected/promoted in youth basketball regardless of their lower functional capacity. Achievement and competitiveness motivation (will to excel and competitiveness) were related to dropping out or persisting in this sample of youth basketball players. Overall, there is a need to consider the interaction between physical growth, biological maturation, functional capacities and behavioural characteristics, specifically among players on the path to sport expertise.

Sex differences in hydration status among adolescent elite soccer players

Hydration of athletes may affect performance and health status likely with differences among sexes. We studied the impact of sex on hydration behaviour in adolescent athletes. Hydration status and urine markers were investigated in 7 female and 7 male elite 16 years-old soccer players in temperate climate (21-24°C). Participants consumed water ad libitum during the first training session (LIB), whereas in the second session (HYD) they drunk a water amount matching 70% of sweat loss from the LIB session. Post-training performances were evaluated by Yo-Yo intermittent recovery level 1 (IR1) test and countermovement jump (CMJ). Body mass values were recorded and urine samples were collected before and after each experimental session. Males drunk a double amount of water in HYD (1.19±0.21 kg) compared to LIB (0.62±0.19 kg; p=0.001; ES=2.88), resulting in a lower percentage body mass loss (HYD -0.95±0.63% versus LIB -1.59±0.33%; p=0.044; ES=-1.35); total distance of Yo-Yo IR1 was higher, albeit not significantly, in HYD (2953±779 m) than in LIB (2103±939 m); CMJ performance was unchanged. In females, water drunk, body mass, Yo-Yo IR1 and CMJ did not vary in HYD versus LIB sessions. In adolescent males a 70% sweat replacement personalized hydration regimen reduced body mass loss and tended to improve performance, whereas in females ad libitum water drinking allowed to maintain hydration status (<1% body mass loss). Our results suggest that coaches and athletes themselves should consider a personalized hydration regimen for adolescent male soccer players, whereas ad libitum drinking seems suitable for females.

Heart Rate Intensity in Female Footballers and its Effect on Playing Position based on External Workload

Introduction: Female football is the world’s fastest developing sport, and due to the rise in magnitude, female football, of all levels, must embrace scientific applications allowing an increase in performance through training, technique and preparation. The purpose of the study was to examine the physiological external workload, of amateur female footballers, across varying heart rate intensities, as well as, interpret fatigue between each half of the Soccer-Specific Aerobic Field Test (SAFT90) protocol. Methods: A sample of n = 24 amateur female football players (mean ± SD; age: 20.7 ± 4.0 years; stretched stature = 165.6 ± 5.8cm, body mass = 58.1 ± 4.7 kg) were recruited during the 2016/2017 competitive season. Maximum heart rate (HRmax) values were determined using the Yo-Yo intermittent recovery level 1 (Yo-Yo IR Level 1) with the SAFT90 protocol used to interpret the physiological and mechanical demands displayed during football match. A one-way analysis of variance was applied to determine the differences between each position (defenders, midfielders and forwards) with the level of significance set at alpha level P < 0.05. Results: There were statistically significant differences between each position and total external workload (F (df:23) = 9.156; (P < 0.05), in addition to average heart rate (HR) across 90 - minutes (F (df:23) = 22.317; (P < 0.05). Statistical significance was also determined differences between each position and the duration of time spent within the prescribed HR intensity zones, including zone 1 (<70% HRmax), zone 2 (70-85% HRmax) and zone 4 (90-95% HRmax) across the SAFT90. The total distance all players completed across the 90 minutes was 10913.7 ± 1076.7 m, whereas the shortest external workload (10020.4 ± 1086.6 m) was completed by defenders and largest (11781.9 ± 324.7 m) by midfielders. The player’s average heart rate was 161.1 ±14.7 bpm-1 resulting in a mean intensity of representing 81% HRmax. Conclusions: Midfielders spent the largest proportion of time between zone 2 and zone 4. Based on these results, coaches are able to determine which type of physiological profile is needed for a specific positon and use this information to design specifically prescribed training programmes to maximise the fitness development.

5-Hydroxymethylfurfural and Alpha-Ketoglutaric Acid as an Ergogenic Aid During Intensified Soccer Training: A Placebo Controlled Randomized Study

Intensified training may lead to fatigue or even a state of overreaching with temporary reductions in performance. Any aid helping to prevent these consequences and to better tolerate such a training regime would be of great importance. 5-hydroxymethylfurfural (5-HMF) and α-ketoglutaric acid (α-KG) supplementation has been suggested to support favorable training outcomes but its effectiveness to facilitate adaptations during an intensified training period has never been investigated. During an in-season competition break (2 weeks), seventeen young outfield soccer players (age:14.7 ± 0.4 yr) performed a 9-day lasting shock microcyle including 5–7 repeated sprint exercise sessions in addition to the regular training (∼6 sessions/wk) and match (1–2 matches/wk) schedule. Before the training period a treadmill test to exhaustion, a YOYO intermittent recovery level 2 (YYIR2) and a repeated sprint ability (RSA) test were performed. The treadmill test was repeated 3 days after the shock microcycle whereas the YYIR2 and the RSA test on day 10 after the training. Magnitude based inference analysis showed likely positive effects of the 5-HMF/α-KG compared to the control group for changes in the maximal running velocity (+0.3 ± 0.7 vs. −0.3 ± 0.8 km/h) and running velocity at lactate turn-point 1 (+0.2 ± 0.4 vs. −0.2 ± 0.6) and lactate turn-point 2 (+0.4 ± 0.4 vs. −0.2 ± 0.6 km/h, for the 5-HMF/α-KG and placebo group, respectively). Training improved YYIR2 performance (+180 ± 67 vs. +200 ± 168m) and RSA (mean time: −0.1 ± 0.1 vs. −0.1 ± 0.1s, for the 5-HMF/α-KG and placebo group, respectively) in both groups and to the same extent. In conclusion, an in-season shock microcyle including repeated sprint training improves YYIR2 performance and RSA in youth soccer players. Supplementation with 5-HMF/α-KG did not modify training adaptations but led to likely positive exercise performance responses shortly after the intensified training regime.

Reliability of Submaximal Yo-Yo Tests in 9- to 16-Year-Old Untrained Schoolchildren.

To examine the reliability of age-adapted submaximal Yo-Yo (Yo-Yosubmax) intermittent tests in untrained schoolchildren aged 9-16 years (n = 139; 72 boys and 67 girls) and within children with high and low percentage of body fat (%BF). Yo-Yo intermittent recovery level 1 children's (YYIR1C), Yo-Yo intermittent endurance level 1 (YYIE1), and Yo-Yo intermittent endurance level 2 (YYIE2) tests were performed 7 days apart by 9- to 11-, 12- to 13-, and 14- to 16-year-old children, respectively. Reliability was tested for Yo-Yosubmax heart rate (HRsubmax), peak HR, and maximal distance. HRsubmax typical errors of measurement (TEM) in YYIR1C, YYIE1, and YYIE2 were 2.2% (1.7%-2.9%), 2.4% (1.9%-3.3%), 1.9% (1.6%-2.5%) and 2.4% (1.9%-3.3%), 2.4% (1.9%-3.2%), 1.9% (1.5%-2.4%) for girls and boys, respectively. HRsubmax intraclass correlation coefficient values were good to excellent (.62-.87) in all age groups and in schoolchildren of different %BF. TEM for HRsubmax ranged from 2.1% to 2.3% in high and low %BF groups. Maximal distance intraclass correlation coefficients were excellent and TEM values ranged from 11% to 12% in both %BF groups. HRsubmax was moderately to largely associated (r = -.46 to -.64; P < .002) with Yo-Yo maximal distance across the age groups. Yo-Yosubmax tests are a reliable tool providing useful and sustainable aerobic performance testing in physical education, irrespective of individual %BF.

The Yo-Yo Intermittent Tests: A Systematic Review and Structured Compendium of Test Results.

Background: Although Yo-Yo intermittent tests are frequently used in a variety of sports and research studies to determine physical fitness, no structured reference exists for comparison and rating of test results. This systematic review of the most common Yo-Yo tests aimed to provide reference values for test results by statistical aggregation of published data.Methods: A systematic literature search for articles published until August 2017 was performed in MEDLINE, Web of Science, SPORTDiscus and Google Scholar. Original reports on healthy females and males ≥16 years were eligible for the analysis. Sub-maximal test versions and the Yo-Yo Intermittent Recovery Level 1 Children's test (YYIR1C) were not included.Results: 248 studies with 9,440 participants were included in the structured analysis. The Yo-Yo test types most frequently used were the Yo-Yo Intermittent Recovery Level 1 (YYIR1, 57.7%), the Yo-Yo Intermittent Recovery Level 2 (YYIR2, 28.0%), the Yo-Yo Intermittent Endurance Level 2 (YYIE2, 11.4%), and the Yo-Yo Intermittent Endurance Level 1 (YYIE1, 2.9%) test. For each separate test, reference values (global means and percentiles) for sports at different levels and both genders were calculated.Conclusions: Our analysis provides evidence that Yo-Yo intermittent tests reference values differ with respect to the type and level of sport performed.The presented results may be used by practitioners, trainers and athletes to rate Yo-Yo intermittent test performance levels and monitor training effects.

Shock microcycle of repeated-sprint training in hypoxia and tennis performance: Case study in a rookie professional player

The aim of this case study was to investigate the effects of a shock microcycle of repeated-sprint training in hypoxia (RSH) on physical fitness and tennis performance. One rookie professional tennis player performed repeated-sprint ability (RSA) and Yo-Yo Intermittent Recovery level 2 (YYIR2) tests before and after (+3 days and +21 days) six sessions of RSH (4 sets of 5 × ∼6 s repeated-shuttle sprint interspersed by ∼24 s of passive recovery) practiced during a 14-day “in-season” period. Tennis performance was subjectively measured from match results and Association of Tennis Professionals (ATP) points obtained during four professional tournaments played before and after intervention. While no changes were found at +3 days post-RSH, improvements in physical fitness (single sprint time (−4.5%), RSA total time (−3.1%) and sprint decrement (−16.7%), as well as YYIR2 total distance covered (+21.4%)) were observable at +21 days post-RSH. Tennis performance obtained during the tournaments was better after intervention. From pre to post-RSH, the decreases in opponents’ ATP ranking during matches won (1109 ± 334 points vs. 818 ± 212 points) and lost (499 ± 68 points vs. 256 ± 58 points) revealed a stronger opposition. Consequently, a three-fold increase (from 4 to 12 ATP points gained from pre to post-RSH) in participant’s ATP ranking was recorded. In summary, a 14-day “in-season” shock microcycle including six sessions of repeated-sprint training in hypoxia revealed interesting effects in specific fitness and tennis performance in a rookie professional tennis player.

Physiological determinants of mixed martial arts performance and method of competition outcome

This investigation sought to determine the relevance of anaerobic and aerobic-based measures to competition level and bout outcome in mixed martial arts competitors. For the primary analysis, seven higher-level and eight lower-level male mixed martial arts competitors were compared across a series of short-term anaerobic (sprints at 10 and 20 m), repeated maximal effort (repeated sprint ability), and intermittent aerobic tests (Yo-Yo Intermittent Recovery Level 2)). For the secondary analysis, data were then pooled so relationships could be explored between test performance and percentage of bouts reaching a decision. Cohen's d effect sizes and qualitative magnitude-based inferences were calculated to describe the differences between groups. These same descriptors were used to interpret the output of the regression analysis used to predict decision percentage. Superior performances by the higher-level group were revealed across most variables to a non-trivial magnitude. Furthermore, it was likely that a decrease in short-term anaerobic performance or an increase in intermittent endurance capacity positively related to an increased likelihood of bouts lasting the full scheduled duration. These findings indicate the importance of anaerobic and aerobic qualities to mixed martial arts performance and combat methods.

The effects of short term detraining and retraining on physical fitness in elite soccer players

PurposeThe aim of this study was to examine the effects of aerobic high-intensity training with reduced volume and training cessation on body composition and physical fitness after the end of season and the time required to recapture physical fitness with intensified retraining following two weeks of detraining in elite soccer players.MethodTwenty male semi-professional soccer players participated in this study. The soccer players were assigned to either a group that completed high-intensity aerobic training (HAT, n = 10) or to a detraining and retraining group (DHAT, n = 10) for a 5-week period immediately after the end of the season. The first 2 weeks of the period, members of the HAT group performed high-intensity aerobic exercise (80–90% of HRmax, 12 min × 3, three times per week), whereas members of the DHAT group abstained from any physical activity. During the subsequent 3 weeks, members of both the HAT and DHAT groups completed high-intensity aerobic exercise. Exercise performance testing and body composition analysis were performed before; after 2 weeks of detraining; and at 1, 2 and 3 weeks of retraining.ResultsIntensified high-intensity training for 5 weeks maintained the performance in the Yo-Yo Intermittent Recovery level 2 test (Yo-Yo IR2) and repeated sprints at any time point (P > 0.05). However 2 weeks of detraining resulted in significant decreases in the performance on the Yo-Yo IR2 (P < 0.01) and repeated sprints test (P < 0.05). Performance on the Yo-Yo IR2 enhanced after 2 weeks of retraining and was maintained up to 3 weeks after retraining, with no significant differences between conditions (P > 0.05). In addition, repeated sprint performance markedly decreased after the detraining period (P < 0.05) and was continuously lower compared to the baseline at 2 weeks after retraining (P < 0.05). Furthermore, this value reached baseline level at the end of the experimental period (P > 0.05). There were no significant differences between conditions in body composition, performance of agility, or sprint ability throughout the 5-week experimental period (P > 0.05).ConclusionsThe present data suggest that short-term detraining after the competitive season can markedly decrease performances in the Yo-Yo IR2 test and repeated sprints. To return to a previous level of ability on the Yo-Yo IR2 and/or sprint test with retraining through high-intensity aerobic training after a period of detraining, a similar or longer period of retraining is required. However, the high-intensity training with reduced amount of training after competitive season can prevent reductions in physical fitness.

Physical performance tests - a relationship of risk factors for muscle injuries in elite level male football players.

The purpose of the present study was to investigate whether there is a relationship between the outcome of preseason physical performance tests and the risk of sustaining lower extremity muscle injuries within the same season, in male football players at elite level. This is a cohort study of a male football team (63 players) from the first league in Swe-den. The football players are prospectively followed, in terms of muscle injuries of the lower extremity during five seasons between 2010 and 2014. All muscle injuries were evaluated and diagnosed with ultraso-nography. The following physical performance tests were included: squats, chin-ups, YoYo intermittent recovery level 2, counter movement jump, squat jump, standing long jump, sprint, one leg squat test, and a functional movement screen. A total of 86 muscle injuries occurred during the study period. No significant correlation was found between the results of the physical performance tests and muscle injuries of the lower extremity. None of the evaluated tests predicted the risk of sus-taining muscle injuries of the lower extremity. We conclude that muscle injury risk factors are more complex than solely related to the results of the preseason physical performance tests.

Exploring Effective Training Methods to Improve Football Performance: Effects of Small Sided Games on Cardiovascular Endurance

This study is aimed to examine the effects of small-sided game training on the cardiovascular endurance among football players. A total of 30 university football players were involved in this study. Participants involved in six weeks of small sided games training and Yo-Yo intermittent recovery level 1 test was conducted pre- and post-training intervention. Descriptive statistics, paired and independent t-test were conducted in data analysis. The results showed that there was a significant difference between the training group and the control group in cardiovascular endurance levels at post-intervention test. In conclusion, a small sided game training is a valuable training method to be implemented in enhancing physical abilities among football players.

Greater Effect of East versus West Travel on Jet Lag, Sleep, and Team Sport Performance.

This study aimed to determine the recovery timeline of sleep, subjective jet lag and fatigue, and team sport physical performance after east and west long-haul travel. Ten physically trained men underwent testing at 0900 h and 1700 h local time on four consecutive days 2 wk before outbound travel (BASE), and the first 4 d after 21 h of outbound (WEST) and return (EAST) air travel across eight time zones between Australia and Qatar. Data collection included performance (countermovement jump, 20-m sprint, and Yo-Yo intermittent recovery level 1 [YYIR1] test) and perceptual (jet lag, motivation, perceived exertion, and physical feeling) measures. In addition, sleep was measured via wrist activity monitors and self-report diaries throughout the aforementioned data collection periods. Compared with the corresponding day at BASE, the reduction in YYIR1 distance after EAST was significantly different from the increase in WEST on day 1 after travel (P < 0.001). On day 2, significantly slower 20-m sprint times were detected in EAST compared with WEST (P = 0.03), with large effect sizes (ES) also indicating a greater reduction in YYIR1 distance in EAST compared with WEST (d = 1.06). Mean sleep onset and offset were significantly later and mean time in bed and sleep duration were significantly reduced across the 4 d in EAST compared with BASE and WEST (P < 0.05). Lastly, mean jet lag, fatigue, and motivation ratings across the 4 d were significantly worse in EAST compared with BASE and WEST (P < 0.05) and WEST compared with BASE (P < 0.05). Long-haul transmeridian travel can impede team sport physical performance. Specifically, east travel has a greater detrimental effect on sleep, subjective jet lag, fatigue, and motivation. Consequently, maximal and intermittent sprint performance is also reduced after east travel, particularly within 72 h after arrival.

Physiological and physical responses to wearing compression garments during soccer matches and recovery.

There is not enough information on the effects of compression therapy in soccer players during recovery after matches. The objective of this study was to examine the effect of wearing compression garments during soccer matches and during recovery period on physical responses. Eighteen semi-professional soccer players participated in this study. A two-stage crossover design was chosen. Participants acted as controls in one match and were assigned to an experimental group (compression stockings group, full-leg compression group, shorts group) in the other match. Participants in experimental groups played the match wearing assigned compression garments and were worn in the 3 days post-match, for 7 hours/day. Blood lactate concentration, arterial oxygen saturation of hemoglobin, perceived exertion, perceived recovery, anaerobic power (vertical jump, sprint, change of direction) and aerobic capacity (Yo-Yo Intermittent Recovery level 2) were measured. Internal and external loads were measured during both matches. Using compression garments may slightly increase lactate during and after soccer matches and only full-leg garments can moderately attenuate the reduction of arterial oxygen saturation of hemoglobin. Wearing compression garments can be useful between 24-48 hours post-exercise to promote psychological recovery, especially with full-leg garments and compression shorts. Decreases in anaerobic power can be attenuated but not significantly, mainly with full-leg compression garments or compression shorts. Compression garments could also have positive effect on aerobic capacity, but we cannot exclude a placebo effect. Compression garments could be moderately beneficial, but effects are not significant.

Reduced severity of lumbo-pelvic-hip injuries in professional Rugby Union players following tailored preventative programmes

ObjectivesThe aim of this study was to tailor lumbo-pelvic-hip (LPH) injury reduction programmes in professional rugby union players based on screening data and examine its effectiveness. DesignProspective case controlled study. MethodsTwenty-eight professional rugby union players were screened pre- and immediately post- the YO-YO intermittent recovery level 1 test using six hip and groin strength tests (adductor squeeze at 0°, 60° and 90°, prone hip extension, abductor, adductor hand held dynamometry). The changes in hip and groin measures, were analysed using hierarchical cluster analysis. Three clusters emerged and a tailored LPH injury reduction programme was administered for each cluster. In addition, 22 players who were not involved in the initial testing received a generic LPH injury reduction programme and were used as the control. Seasonal information for LPH injury incidence, severity and prevalence were compared to the previous season. ResultsThe same number of injuries were observed when the prospective injury surveillance data was compared to the previous season, however a reduced injury severity (936days vs 468days), average severity (78±126days vs 42±37days) and prevalence (21% vs 19%) were found. Moreover, LPH injury severity for players who were prescribed a tailored injury reduction programme (209days) were 50days less than players given a generic LPH injury reduction programme (259days). ConclusionsOur preliminary observations support the effectiveness of grouping players and tailoring intervention based on common group characteristics in reducing the severity of LPH injuries in professional Rugby Union.

Growth, functional capacities and motivation for achievement and competitiveness in youth basketball: an interdisciplinary approach

ABSTRACTThe interaction of multiple influences on the path to sport success is not yet fully understood by sport scientists. In this study, we examined variation in body size, functional capacities and motivation for achievement, competitiveness and deliberate practice of youth basketball players associated with differences in biological maturity status, chronological age and years of training experience. Reflecting the importance of interactive effects, we examined the relationships between the psychological variables and functional capacities. Fifty-eight male basketball players aged 9.5 to 15.5 years were considered. Variables included chronological age, estimated age at peak height velocity, stature, body mass and sitting height by anthropometry; the Work and Family Orientation and Deliberate Practice Motivation Questionnaires were also used. Finally, the Line Drill test and Yo-Yo Intermittent Recovery level 1 (Yo-Yo IR1) tests were used as functional capacities indicators for basketball. Variance components models derived from series of multilevel linear regression models revealed a substantial variation by maturity status for body size, functional capacities indicators, mastery and will to excel. The influence of estimated maturity status on mastery and will to excel was independent of age and years of experience. In contrast, no relationships were observed between psychological variables and functional capacities indicators. We conclude that growth-related changes are relevant to understanding players´ motivations for achievement, competitiveness and deliberate practice. This should be of interest to those involved in the selection and development of youth basketball players.

Physical Fitness and Body Composition in 8-10-Year-Old Danish Children Are Associated With Sports Club Participation.

Larsen, MN, Nielsen, CM, Ørntoft, CØ, Randers, M, Manniche, V, Hansen, L, Hansen, PR, Bangsbo, J, and Krustrup, P. Physical fitness and body composition in 8–10-year-old Danish children are associated with sports club participation. J Strength Cond Res 31(12): 3425–3434, 2017—We investigated whether physical fitness and body composition in 8–10-year-old Danish children are associated with sports club participation. The study included 423 schoolchildren, comprising 209 girls and 214 boys, of whom 67 and 74%, respectively, were active in sports clubs. Yo-Yo intermittent recovery level 1 for children (YYIR1C), balance, jump and coordination tests, together with dual-energy X-ray absorptiometry, were used to determine exercise capacity and body composition. Children active in sports clubs had better (p < 0.05) YYIR1C (33%, 767 ± 26 vs. 575 ± 29 m), 20-m sprint (3%, 4.33 ± 0.03 vs. 4.48 ± 0.04 seconds), coordination (6%, 68 ± 1 vs. 72 ± 1 second), and balance test performances (9%, 19.3 ± 0.5 vs. 21.2 ± 0.7 falls·min−1) and lower fat mass index (16%, 3.8 ± 0.1 vs. 4.5 ± 0.2 kg[fat]·m−2) than children not active in sports clubs. Ball game players had better (p < 0.05) YYIR1C (38%, 925 ± 39 vs. 671 ± 28 m), 20-m sprint (4%, 4.25 ± 0.03 vs. 4.42 ± 0.04 seconds), and coordination test performances (5%, 65 ± 1 vs. 69 ± 1 second), along with higher (p < 0.05) lean body mass (5%, 24.00 ± 0.22 vs. 22.83 ± 0.25 kg) and whole-body BMD (2%, 0.90 ± < 0.01 vs. 0.88 ± <0.01 g·cm−2) compared with children active in other sports. The study showed that 8‒10-year-old Danish children engaged in sports-club activity, especially ball game players, have better exercise capacity and superior body composition compared with children not active in sports clubs.

Hypoxic Repeat Sprint Training Improves Rugby Player's Repeated Sprint but Not Endurance Performance.

This study aims to investigate the performance changes in 19 well-trained male rugby players after repeat-sprint training (six sessions of four sets of 5 × 5 s sprints with 25 s and 5 min of active recovery between reps and sets, respectively) in either normobaric hypoxia (HYP; n = 9; FIO2 = 14.5%) or normobaric normoxia (NORM; n = 10; FIO2 = 20.9%). Three weeks after the intervention, 2 additional repeat-sprint training sessions in hypoxia (FIO2 = 14.5%) was investigated in both groups to gauge the efficacy of using “top-up” sessions for previously hypoxic-trained subjects and whether a small hypoxic dose would be beneficial for the previously normoxic-trained group. Repeated sprint (8 × 20 m) and Yo-Yo Intermittent Recovery Level 1 (YYIR1) performances were tested twice at baseline (Pre 1 and Pre 2) and weekly after (Post 1–3) the initial intervention (intervention 1) and again weekly after the second “top-up” intervention (Post 4–5). After each training set, heart rate, oxygen saturation, and rate of perceived exertion were recorded. Compared to baseline (mean of Pre 1 and Pre 2), both the hypoxic and normoxic groups similarly lowered fatigue over the 8 sprints 1 week after the intervention (Post 1: −1.8 ± 1.6%, −1.5 ± 1.4%, mean change ± 90% CI in HYP and NORM groups, respectively). However, from Post 2 onwards, only the hypoxic group maintained the performance improvement compared to baseline (Post 2: −2.1 ± 1.8%, Post 3: −2.3 ± 1.7%, Post 4: −1.9 ± 1.8%, and Post 5: −1.2 ± 1.7%). Compared to the normoxic group, the hypoxic group was likely to have substantially less fatigue at Post 3–5 (−2.0 ± 2.4%, −2.2 ± 2.4%, −1.6 ± 2.4% Post 3, Post 4, Post 5, respectively). YYIR1 performances improved throughout the recovery period in both groups (13–37% compared to baseline) with unclear differences found between groups. The addition of two sessions of “top-up” training after intervention 1, had little effect on either group. Repeat-sprint training in hypoxia for six sessions increases repeat sprint ability but not YYIR1 performance in well-trained rugby players.

Selected Physiological Profile among Malaysian 3rd Tier Fam League Football Players

The purpose of this study was to determine physiological profile of body composition, power, speed, agility, VO₂max, anaerobic capacity and muscular endurance of Malaysian 3rd tier football league players based on four different positions named goalkeepers, defenders, midfielders and strikers. An ex post facto design was employed. Twenty eight [ n: 28; mean (?SD) age 24.78 (?3.28); height 172.69 (?4.63) cm; and weight 71.19 (? 8.42) kg]? of footballers of Sime Darby FC participated with different positions of play in the field (goalkeeper: 4, defender: 11, midfielder: 8, striker: 5). The fitness testing involved were anthropometrics which include skinfold test, squat vertical jump, 30 meters maximal sprint, Illinois agility run test, Yo-Yo intermittent recovery level 1 test, repeated sprint ability test, and maximum push up test. All testing were in accordance to standard procedures. Inferential analysis was carried out using one-way ANOVA and Tukey post hoc to reveal the sources of significant with p