Yo-Yo Intermittent Endurance Test Research Articles

Acute ischemic preconditioning does not influence high-intensity intermittent exercise performance.

This study evaluated the acute effect of ischemic preconditioning (IPC) on a high-intensity intermittent exercise performance and physiological indicators in amateur soccer players. Thirteen players (21.5 ± 2 yrs) attended three trials separated by 3–5 days in a counterbalanced randomized cross-over design: IPC (4 × 5-min occlusion 220 mmHg/reperfusion 0 mmHg) in each thigh; SHAM (similar to the IPC protocol but “occlusion” at 20 mmHg) and control (seated during the same time of IPC). After 6-min of each trial (IPC, SHAM or control), the players performed the YoYo Intermittent Endurance Test level 2 (YoYoIE2). The distance covered in the YoYoIE2 (IPC 867 ± 205 m; SHAM 873 ± 212 m; control 921 ± 206 m) was not different among trials (p = 0.10), furthermore, lactate concentration and rate of perceived exertion did not differ (P > 0.05) among protocols. There were also no significant differences in either mean heart rate (HR) or peak HR (p > 0.05) for both IPC and SHAM compared to control. Therefore, we conclude that acute IPC does not influence high-intensity intermittent exercise performance in amateur soccer players and that rate of perceived exertion, heart rate and lactate do not differ between the intervention IPC, SHAM and control.

Fitness and health benefits of team handball training for young untrained women—A cross-disciplinary RCT on physiological adaptations and motivational aspects

PurposeThe present study evaluated the effects of regular participation in small-sided team handball training on body composition, osteogenic response, physical performance, and cardiovascular risk factors, as well as well-being and motivation, in young untrained women. MethodsTwenty-eight untrained 20- to 30-year-old women were randomized to a handball training group (HG; n = 14, height 170 ± 5 cm, weight 73 ± 11 kg, VO2peak 37.7 ± 4.1 mL/min/kg) that trained 1.7 ± 0.3 times per week over 12 weeks (70 min 4 v 4 handball sessions) or an inactive control group (CG; n = 14, 169 ± 5 cm, 71 ± 12 kg, 38.1 ± 3.7 mL/min/kg). Physiological and psychological and motivational training adaptations were assessed pre- and post-intervention by dual-energy X-ray Absorptiometry (DXA) scans, blood sampling, physical tests, and questionnaires. ResultsThe average heart rate (HR) over all training sessions was equal to 85% ± 6% HRmax. Between-group intervention effects were observed in favor of HG for muscle mass (2.1%, p = 0.024), proximal femur bone mineral density (0.8%, p = 0.041), Yo-Yo IE1 intermittent endurance test level 1 (IE1) performance (35%, p < 0.001), and incremental treadmill test performance (11.5%, p = 0.003), but not total fat mass (p = 0.176), mean arterial blood pressure (p = 0.328), resting HR (p = 0.219), or blood lipids (p = 0.298–0.854). In CG, no changes were observed in any of the measured physiological variables after the training period. Compared to CG, HG had an increase in intrinsic motivation (p < 0.001) and in the well-being subscale “energy” (p = 0.010). ConclusionParticipation in regular recreational team handball training organized as small-sided games has marked beneficial effects on physical performance, musculoskeletal fitness, well-being, and motivation in untrained young women.

The effects of menstrual cycle phase on physical performance in female soccer players.

BackgroundFemale soccer has grown extensively in recent years, however differences in gender-specific physiology have rarely been considered. The female reproductive hormones which rise and fall throughout the menstrual cycle, are known to affect numerous cardiovascular, respiratory, thermoregulatory and metabolic parameters, which in turn, may have implications on exercise physiology and soccer performance. Therefore, the main aim of the present study was to investigate potential effects of menstrual cycle phase on performance in soccer specific tests.MethodsNine sub elite female soccer players, all of whom have menstrual cycles of physiological length; performed a series of physical performance tests (Yo-Yo Intermittent endurance test (Yo-Yo IET), counter movement jump (CMJ) and 3x30 m sprints). These were conducted at distinct time points during two main phases of the menstrual cycle (early follicular phase (FP) and mid luteal phase (LP)) where hormones contrasted at their greatest magnitude.ResultsYo-Yo IET performance was considerably lower during the mid LP (2833±896 m) as compared to the early FP (3288±800 m). A trend towards significance was observed (p = 0.07) and the magnitude based inferences suggested probabilities of 0/61/39 for superiority/equality/inferiority of performance during the mid LP, leading to the inference of a possibly harmful effect. For CMJ (early FP, 20.0±3.9 cm; mid LP 29.6±3.0 cm, p = 0.33) and sprint (early FP, 4.7±0.1 s; mid LP, 4.7±0.1 s, p = 0.96) performances the results were unclear (8/24/68, 48/0/52, respectively).ConclusionThe results of this study are in support of a reduction in maximal endurance performance during the mid LP of the menstrual cycle. However, the same effect was not observed for jumping and sprint performance. Therefore, consideration of cycle phase when monitoring a player’s endurance capacity may be worthwhile.

Adaptations with Intermittent Exercise Training in Post- and Premenopausal Women.

The purposes of the present study was to examine the effect of intermittent exercise training on musculoskeletal and metabolic health in postmenopausal (PM) and premenopausal (PRM) women and, furthermore, to evaluate whether the adaptations can be maintained with a reduced training frequency. Eighteen PM (51 ± 1 yr, mean ± SEM) and 12 PRM (48 ± 1 yr) women participated in floorball training approximately two times per week for 12 wk. In a subgroup (n = 9) of PM women (PM40), exercise training was performed for an additional 40 wk with a reduced training frequency of approximately one training session per week. In PM, the body fat percentage decreased (P < 0.05) and the total lean leg mass increased (P < 0.05) during the 12-wk training period, with no changes in PRM. In both PM and PRM, lean body mass and maximal oxygen uptake (V˙O2max) were higher, and Yo-Yo intermittent endurance test 1 (YYIET-1) performance was better (P < 0.05) after the 12-wk training period. Procollagen type 1 amino-terminal propeptide was higher (P < 0.05) in PM, and total leg bone mineral density (BMD) was higher (P < 0.05) in both PM and PRM after the 12-wk training period. In PM40, total lean leg mass, V˙O2max, YYIET-1 performance, level of procollagen type 1 amino-terminal propeptide, and total leg BMD were maintained, whereas whole-body BMD and glycated hemoglobin (HbA1c) were reduced (P < 0.05) and the expression of muscle glucose transporter type 4 was higher (P < 0.05). Twelve weeks of intermittent exercise training increased BMD, intermittent exercise capacity, and V˙O2max in PM and PRM, with PM also having positive changes in body composition. Additional 40 wk of training with a reduced frequency was sufficient to preserve these physiological adaptations and also improve blood glucose regulation in PM.

Heart Rate and Energy Expenditure in Division I Field Hockey Players During Competitive Play.

Sell, KM and Ledesma, AB. Heart rate and energy expenditure in Division I field hockey players during competitive play. J Strength Cond Res 30(8): 2122-2128, 2016-The purpose of this study was to quantify energy expenditure and heart rate data for Division I female field hockey players during competitive play. Ten female Division I collegiate field hockey athletes (19.8 ± 1.6 years; 166.4 ± 6.1 cm; 58.2 ± 5.3 kg) completed the Yo-Yo intermittent endurance test to determine maximal heart rate. One week later, all subjects wore a heart rate monitor during a series of 3 matches in an off-season competition. Average heart rate (AvHR), average percentage of maximal heart rate (AvHR%), peak exercise heart rate (PExHR), and percentage of maximal heart rate (PExHR%), time spent in each of the predetermined heart rate zones, and caloric expenditure per minute of exercise (kcalM) were determined for all players. Differences between positions (backs, midfielders, and forwards) were assessed. No significant differences in AvHR, AvHR%, PExHR, PExHR%, and %TM were observed between playing positions. The AvHR% and PExHR% for each position fell into zones 4 (77-93% HRmax) and 5 (>93% HRmax), respectively, and significantly more time was spent in zone 4 compared with zones 1, 2, 3, and 5 across all players (p ≤ 0.05). The kcalM reflected very heavy intensity exercise. The results of this study will contribute toward understanding the sport-specific physiological demands of women's field hockey and has specific implications for the duration and schedule of training regimens.

Anthropometric, speed and endurance characteristics of English academy soccer players: Do they influence obtaining a professional contract at 18 years of age?

This study evaluated the anthropometric, speed and endurance characteristics of English academy soccer players, comparing players who obtained a ‘professional’ contract at 18 years old with those that did not (‘academy’); 443 male academy soccer players from an English professional club undertook anthropometric (height and body mass), speed (10 and 20 m sprint) and endurance (Yo-Yo intermittent endurance test level 2 [Yo-Yo]) assessments between 2005 and 2012. Significant improvements with age were found for speed and endurance at each annual age group up until U18 age category. Significant differences were only observed between ‘professional’ and ‘academy’ players for 10 m ( p = 0.003, η2 = 0.01) and 20 m ( p = 0.001, η2 = 0.01) speed at U16 and U18 and Yo-Yo performance ( p = 0.001, η2 = 0.12) at U18 age category. Practitioners should use speed and endurance assessments for monitoring physical development of players rather than for talent identification purposes.

Regular Football Practice Improves Autonomic Cardiac Function in Male Children.

Background:The role of the autonomic nervous system (ANS) in the cardiovascular regulation is of primal importance. Since it has been associated with adverse conditions such as cardiac arrhythmias, sudden death, sleep disorders, hypertension and obesity.Objectives:The present study aimed to investigate the impact of recreational football practice on the autonomic cardiac function of male children, as measured by heart rate variability.Patients and Methods:Forty-seven male children aged 9 - 12 years were selected according to their engagement with football oriented practice outside school context. The children were divided into a football group (FG; n = 22) and a control group (CG; n = 25). The FG had regular football practices, with 2 weekly training sessions and occasional weekend matches. The CG was not engaged with any physical activity other than complementary school-based physical education classes. Data from physical activity, physical fitness, and heart rate variability measured in time and frequency domains were obtained.Results:The anthropometric and body composition characteristics were similar in both groups (P > 0.05). The groups were also similar in time spent daily on moderate-to-vigorous physical activities (FG vs. CG: 114 ± 64 vs. 87 ± 55 minutes; P > 0.05). However, the FG performed better (P < 0.05) in Yo-Yo intermittent endurance test (1394 ± 558 vs. 778 ± 408 m) and 15-m sprint test (3.06 ± 0.17 vs. 3.20 ± 0.23 s). Also, the FG presented enhanced autonomic function. Significant differences were detected (P < 0.05) between groups for low frequency normalized units (38.0 ± 15.2 vs. 47.3 ± 14.2 n.u (normalized units)), high frequency normalized units (62.1 ± 15.2 vs. 52.8 ± 14.2 n.u.), and LF:HF ratio (0.7 ± 0.4 vs. 1.1 ± 0.6 ms2).Conclusions:Children engaged with regular football practice presented enhanced physical fitness and autonomic function, by increasing vagal tone at rest.

Effects of Plyometric and Sprint Training on Physical and Technical Skill Performance in Adolescent Soccer Players.

To determine the influence of a short-term combined plyometric and sprint training (9 weeks) within regular soccer practice on explosive and technical actions of pubertal soccer players during the in-season. Twenty-six players were randomly assigned to 2 groups: control group (CG) (soccer training only) and combined group (CombG) (plyometric + acceleration + dribbling + shooting). All players trained soccer 4 times per week and the experimental groups supplemented the soccer training with a proposed plyometric-sprint training program for 40 minutes (2 days per weeks). Ten-meter sprint, 10-m agility with and without ball, CMJ and Abalakov vertical jump, ball-shooting speed, and Yo-Yo intermittent endurance test were measured before and after training. The experimental group followed a 9-week plyometric and sprint program (i.e., jumping, hurdling, bouncing, skipping, and footwork) implemented before the soccer training. Baseline-training results showed no significant differences between the groups in any of the variables tested. No improvement was found in the CG; however, meaningful improvement was found in all variables in the experimental group: CMJ (effect size [ES] = 0.9), Abalakov vertical jump (ES = 1.3), 10-m sprint (ES = 0.7-0.9), 10-m agility (ES = 0.8-1.2), and ball-shooting speed (ES = 0.7-0.8). A specific combined plyometric and sprint training within regular soccer practice improved explosive actions compared with conventional soccer training only. Therefore, the short-term combined program had a beneficial impact on explosive actions, such as sprinting, change of direction, jumping, and ball-shooting speed which are important determinants of match-winning actions in soccer performance. Therefore, we propose modifications to current training methodology for pubertal soccer players to include combined plyometric and speed training for athlete preparation in this sport.

A Validation Study For Sport-specific Aerobic Fitness Testing In Soccer Players.

Aerobic fitness is an important component in soccer performance. However, aerobic fitness assessment in soccer is primarily via non-sport-specific tests. The Hoff test, a soccer specific training tool was first proposed in 2002 but has since been modified for aerobic fitness assessment. However, test validity and reliability have yet to be quantified. PURPOSE: The primary aim of the study was to compare the Hoff test with more established aerobic fitness tests. A secondary aim was to quantify test-retest reliability. METHODS: 15 soccer players (13 male, 2 female; Age 23±5yrs) completed three separate trials. During trial 1, subjects completed the Hoff test and the Yo-yo intermittent endurance test 2 (YYIET2). During trial 2, subjects repeated the Hoff test. An incremental treadmill test was performed during trial 3. Total distance was recorded for the Hoff and YYIET2 tests. Maximal heart rate (HRmax) and final blood lactate (BLa) were measured as physiological responses to each test. Metabolic data were collected during the treadmill test in order to quantify VO2max. Paired Student’s T-tests compared Hoff test distance, YYIET2 distance and VO2max. Intra-class Correlation Coefficients (ICC) and Technical Error of the Measurement (TEM) quantified test reliability. RESULTS: Group mean ± SD Hoff test distance, YYIET2 distance and VO2max were 1497±234m, 1201±661.5m and 50.8±9.0ml.kg-1.min-1, respectively. BLa and HRmax were not significantly different between test modalities. Hoff Test distance was very high correlated with VO2max (r=0.91). YYIET2 distance was also highly correlated with VO2max (r=0.86) and Hoff test distance (r=0.89). ICC and TEM for Hoff test distance were 0.931 and 4.34% respectively. A significant difference between Hoff test 1 and 2 distances was observed (1439 ± 256m vs. 1497 ± 234m; P<0.01). CONCLUSIONS: The results of this study indicate that the Hoff test is a reliable test that is highly correlated with more established aerobic fitness tests in soccer players. Linear regression analysis suggests that distance covered in the Hoff Test can provide a strong prediction of VO2max. However, a conditioning effect was observed between Hoff tests, suggesting that players require greater test familiarization prior to running the Hoff test in order to produce accurate results.

Effect of Strength and High-Intensity Training on Jumping, Sprinting, and Intermittent Endurance Performance in Prepubertal Soccer Players

Ferrete, C, Requena, B, Suarez-Arrones, L, and Sáez de Villarreal, E. Effect of strength and high-intensity training on jumping, sprinting, and intermittent endurance performance in prepubertal soccer players. J Strength Cond Res 28(2): 413–422, 2014—The purpose of this study was to examine the effects of a 26-week on-field combined strength and high-intensity training on the physical performance capacity among prepubertal soccer players who were undertaking a competitive phase of training. Twenty-four prepubertal soccer players between the age of 8 and 9 years were randomly assigned to 2 groups: a control (C; n = 13) and an experimental group (S; n = 11). Both groups performed an identical soccer-training program, whereas the S group also performed combined strength and high-intensity training before the soccer-specific training. The 15-m sprint time (seconds), countermovement jump (CMJ) displacement, Yo-Yo intermittent endurance test (Yo-Yo IE), and Sit and Reach flexibility were each measured before (baseline) and after 9 (T2), 18 (T3), and 26 weeks (posttest) of training. There were no significant differences between the groups in any of the variables tested at baseline. After 26 weeks, significant improvements were found in the CMJ (6.72%; effect size [ES] = 0.37), Yo-Yo IE (49.57%, ES = 1.39), and Flexibility (7.26%; ES = 0.37) variables for the S group. Conversely, significant decreases were noted for the CMJ (−10.82%; ES = 0.61) and flexibility (−13.09%; ES = 0.94) variables in the C group. A significant negative correlation was found between 15-m sprint time and CMJ (r = −0.77) and Yo-Yo IE (r = −0.77) in the S group. Specific combined strength and high-intensity training in prepubertal soccer players for 26 weeks produced a positive effect on performance qualities highly specific to soccer. Therefore, we propose modifications to current training methodology for prepubertal soccer players to include strength and high-intensity training for athlete preparation in this sport.

The investigation of heart rate variation on endurance of professional soccer players

The main aim of the present study was to determine whether performance on the Yo-Yo intermittent endurance test can predict the real match performances, or not. The sample of players consists of elite professional soccer players (age 23.02±4.49 years, soccer experience 10.04±4.2 years, body mass 73.61±6,15 kg, height 1,79 ±0,52 m, body mass index 19,12 ±0,4 kg m , body fat 8,32 ±2,96 %) who were the members of the 2 Turkish Soccer Federation. For assessment of aerobic endurance performance used, the Yo-Yo intermittent endurance test level 1 was performed. Heart rate was recorded by a Polar Vantage NV heart rate monitor placed around the chest for continuous heart rate recordings throughout selected stages of the test. Descriptive statistics were calculated. Data are expressed as means and standard deviations for each variable. It is seen that the research group uses 83 % of MaxHR in average Heart Rate according to minimum, average and maximum HR values obtained according to max HR values of the research group. As a conclusion, it is understood that heart rate is an important factor obtained from the yo-yo test that the soccer players show similar efforts during the competition. So the heart rate values taken from this test used as intermittent test has the quality to estimate the players match performance.

Attributes of Top Elite Team-Handball Players

Researchers in the field of excellence in sport performance are becoming increasingly focused on the study of sport-specific characteristics and requirements. In accordance with this, the purposes of this study were (a) to examine the morphologic-, fitness-, handball-specific skills and psychological and "biosocial" differences between top elite and nontop elite team-handball players and (b) to investigate the extent to which they may be used to identify top elite team-handball players. One hundred sixty-seven adult male team-handball players were studied and divided in 2 groups: top elite (n = 41) and nontop elite (n = 126). Twenty-eight morphologic-, 9 fitness-, 1 handball-specific skills and 2 psychological-based and 2 "biosocial"-based attributes were used. Top elite and nontop elite groups were compared for each variable of interest using Student's t-test, and 5 logistic regression analyses were performed with the athlete's performance group (top elite or nontop elite) as the dependent variable and the variables of each category as predictors. The results showed that (a) body mass, waist girth, radiale-dactylion length, midstylion-dactylion length, and absolute muscle mass (morphologic model); (b) 30-m sprint time, countermovement jump height and average power, abdominal strength and the class of performance in the Yo-Yo Intermittent Endurance Test (fitness model); (c) offensive power (specific-skills model); (d) ego-based motivational orientation (psychological model); (e) socioeconomic status and the energy spent (for week) in handball activity (biosocial model); significantly (p < 0.05) contributed to predict the probability of an athlete to be a top elite team-handball player. Moreover, the fitness model exhibited higher percentages of correct classification (i.e., 91.5%) than all the other models did. This study provided (a) the rational to reduce the battery of tests for evaluation purposes, and (b) the initial step to work on building a multidisciplinary model to predict the probability of a handball athlete to be a top elite player.

Match performance and physical capacity of players in the top three competitive standards of English professional soccer

The aim of this study was to compare the match performance and physical capacity of players in the top three competitive standards of English soccer. Match performance data were collected from players in the FA Premier League (n=190), Championship (n=155) and League 1 (n=366) using a multiple-camera system. In addition, a selection of players from the Premier League (n=56), Championship (n=61) and League 1 (n=32) performed the Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2) to determine physical capacity. Players in League 1 and the Championship performed more (p<.01) high-intensity running than those in the Premier League (Effect Size [ES]: 0.4–1.0). Technical indicators such as pass completion, frequency of forward and total passes, balls received and average touches per possession were 4–39% higher (p<.01) in the Premier League compared to lower standards (ES: 0.3–0.6). Players also covered more (p<.05) high-intensity running when moving down (n=20) from the Premier League to the Championship (ES: 0.4) but not when players moved up (n=18) standards (ES: 0.2). Similar Yo-Yo IE2 test performances were observed in Premier League, Championship and League 1 players (ES: 0.2–0.3). Large magnitude relationships (p<.05) were observed between Yo-Yo IE2 test performances and the total and high-intensity running distance covered in both Championship (r=.56 and .64) and Premier League matches (r=.61 and .54). The data demonstrate that high-intensity running distance was greater in players at lower compared to higher competitive standards despite a similar physical capacity in a subsample of players in each standard. These findings could be associated with technical characteristics inherent to lower standards that require players to tax their physical capacity to a greater extent but additional research is still required to confirm these findings.

O nível de condicionamento físico afeta a magnitude da carga interna de treinamento em jovens jogadores de basquetebol?

ObjectiveThe aim of this study was to investigate the influence of the ability to perform high intensity effort (HIE) on internal training load (CIT) responses in young basketball players. MethodTwelve male basketball players took part of the investigation (18.6 ± 0.5 years, 192 ± 6.5cm e 88.8 ± 14.5kg). The investigation lasted four weeks, with two weeks of a preparatory period (PP) and two weeks of a competitive period (PC). Session ratings of perceived exertion (session-RPE) method was used to quantify internal training load in every training session. Athletes performed the Yo-Yo Intermittent Endurance Test level 2 (Yo-Yo IE2) before and after the experimental period (4 weeks). For data analysis, Pearson correlation coefficient was used (Yo-Yo IE2 [PRE and POST] x CIT [General (PP and PC), PP and PC]) (p<0.05). ResultsNegative correlation coefficients, classified as “large” to “very large”, were observed between the performance in the Yo-Yo IE2 PRE and ITL in PP (r=–0.81), CP (r=–0.72), and in the whole experimental period (PP and CP) (r=–0.80) conditions. Correlation coefficients, classified as “large” to “very large”, were also observed between the performance in the Yo-Yo IR2 POST and ITL during PP (r=–0.83), CP (r=–0.66) and General (r=–0.78) conditions. ConclusionThe results of the present study suggest the existence of a strong correlation between the ability to perform HIE and ITL, thus indicating the importance of adopting an integrated monitoring of these variables, aiming to conduct regular adjustments on training load.

Responsiveness of the One-Leg Hop Test and the Square Hop Test to Fatiguing Intermittent Aerobic Work and Subsequent Recovery

The purpose of the present study was to evaluate the responsiveness of the 1-leg hop test and the square hop (SH) test to fatiguing intermittent aerobic work and during recovery. A further aim was to study sex differences in trends. Members of 4 sub-elite-level soccer teams were invited to participate. Ten men (mean ± SD) aged 20.7 ± 3.4 years and 10 women aged 21.8 ± 4.8 years accepted to participate in the test. The Yo-Yo intermittent Endurance test Level 2, was used as a standardized sport-specific fatiguing protocol. The 1-leg hop test and the SH test were performed before, immediately after, 15, and 30 minutes after the fatiguing exercise. To quantify the level and progression of fatigue and recovery, blood lactate and heart rate were measured, and general fatigue was estimated on Borg's rating of perceived exertion scale. No significant difference in performance in either of the hop tests was found immediately after intermittent aerobic fatiguing work. Performance in the 1-leg hop test significantly decreased (p = 0.002), whereas that in the SH test increased (p = 0.001) between baseline and 15-30 minutes after fatiguing work. No significant difference in trends between sexes was found. The performance in the 1-leg hop test significantly decreased during 30 minutes of recovery compared with that in the nonfatigued conditions and might therefore be used on the field as a complement to other physical parameters to detect remaining fatigue. Note that the 1-leg hop test did not immediately respond to intermittent aerobic work. It is not recommended to use the SH test for measuring fatigue and subsequent recovery because the performance constantly increased despite the present objective and subjective fatigue.

Role of Free Testosterone in Interpreting Physical Performance in Elite Young Brazilian Soccer Players

This study investigated the contribution of salivary testosterone (sT) concentration, years from peak height velocity (YPHV) and height by body mass interaction on jumping performance (Countermovement jump; CMJ) and aerobic fitness (Yo-Yo intermittent endurance test, level 1) in young elite soccer players. Forty-five participants (age: 12.5 ± 0.5 y; body mass: 48.6 ± 10.2 kg, height: 155.7 ± 10.0cm) belonging to a top level Brazilian soccer club were evaluated at four time points across a single semester. None of the assessed players had reached PHV. The data from the four evaluations were averaged and multiple linear regression analysis conducted. For CMJ, the model explained 42.88% of the variance (R2 = 42.88; p < .000); sT concentration was the primary contributor (R2 = 32.84) and the YPHV contributed 9.95% of the variance. The model explained 28.50% (p < .000) of the variance in Yo-Yo. The sT was the primary and single significant contributor (R2 = 21.32). A significant difference was noted between high and low testosterone groups divided a posteriori to CMJ performance (t = 3.35; p = .001). These results suggest an important role for hormonal status in interpreting physical performance in preadolescent soccer players.

Anthropometric Characteristics, Physical Fitness and Technical Performance of Under-19 Soccer Players by Competitive Level and Field Position

Anthropometric characteristics, physical fitness and technical skills of under-19 (U19) soccer players were compared by competitive level (elite, n=95; non-elite, n=85) and playing position (goalkeeper, central defender, fullback, midfield, forward). Fitness tests included 5- and 30-m sprints, agility, squat jump (SJ) and countermovement jump (CMJ), strength and Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2). Soccer-specific skills included ball control and dribbling. Independent of position, elite players presented more hours of training per year than non-elite players (d>1.2). Stature and body mass discriminated elite from non-elite players among goalkeepers and central defenders (d>0.6). Major differences were noted between elite and non-elite goalkeepers for SJ, CMJ, Yo-Yo IE2, and ball control (d>1.2). Elite central defenders performed better than their non-elite counterparts in SJ and ball control tests (d>1.2). Elite players presented better agility and Yo-Yo IE2 performances than non-elite players within all positional roles (d>0.6). In conclusion, U19 players differed in anthropometric characteristics, physical fitness and technical skills by competitive level within field positions.

The Application of the Yo‐Yo Intermittent Endurance Level 2 Test to Elite Female Soccer Populations

The aim of this study was to evaluate the application of the Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2) to elite female soccer populations. Elite senior (n = 92), youth (n = 42), domestic (n = 46) and sub-elite female soccer players (n = 19) carried out the Yo-Yo IE2 test on numerous occasions across the season. Test-retest coefficient of variation (CV) in Yo-Yo IE2 test performance in domestic female players was 4.5%. Elite senior female players' Yo-Yo IE2 test performances were better (P < 0.01) than elite youth, domestic and sub-elite players (mean ± standard deviation; 1774 ± 532 vs 1490 ± 447, 1261 ± 449, and 994 ± 373 m). For elite senior female players, wide midfielders (2057 ± 550 m) had a higher Yo-Yo IE2 test performance (P < 0.05) than central defenders (1588 ± 534 m) and attackers (1516 ± 401 m), but not central midfielders (1764 ± 473 m) or full-backs (1964 ± 522 m). Large correlations were observed between Yo-Yo IE2 test performance and the total and high-intensity distance covered (r = 0.55; P < 0.05) during elite senior soccer matches (r = 0.70; P < 0.01). A large correlation was also obtained between Yo-Yo IE2 test performance and (r = 0.68; P < 0.01). Performances in the Yo-Yo IE2 test were greater (P < 0.05) in the middle and the end of the season compared with the preparation period for elite youth female players (1767 ± 539 and 1742 ± 503 vs 1564 ± 504 m) and in elite senior female players, Yo-Yo IE2 test performance increased by 14% (P < 0.01) after completing 4 weeks of intense training prior to the FIFA Women's World Cup Finals (2049 ± 283 vs 1803 ± 342 m). The data demonstrate that the Yo-Yo IE2 test is reproducible and is an indicator of the match-specific physical capacity of female soccer players. Furthermore, the Yo-Yo IE2 test illustrates sensitivity by differentiating intermittent exercise performance of female players in various competitive levels, stages of the season and playing positions.

Individual Match Playing Time During the Season Affects Fitness-Related Parameters of Male Professional Soccer Players

The purpose of this study was to analyze the effects of an entire season on physical fitness parameters (PFPs) in male professional soccer players (N = 18). Performance in 5- and 30-m sprint (T5 and T30), countermovement jump (CMJ), agility (T-test), knee extensor (KE) and knee flexor (KF) isokinetic strength, hamstrings/quadriceps strength ratio (H/Q) and bilateral differences (BDs), and Yo-Yo intermittent endurance test 2 (YYIE2) was evaluated in 4 moments (E1-E4) throughout the season. Individual match playing time was quantified. Significant improvements in CMJ and YYIE2 from E1 to E2 were observed (p < 0.05-0.01). The T30 improved from E2 to E3 (p < 0.01). The CMJ decreased from E2 to E3 and E4, and YYIE2 from E2 to E4 (p < 0.05). There were increments in the H/Q ratio and Agility from E1 and E2 to E3 and E4 (p < 0.05-0.01). Significant correlations were found in all evaluation points between different PFPs and between changes in strength parameters and agility, T5 and T30, CMJ, and YYIE2 (p < 0.05-0.001). Influence of individual match playing time was correlated to changes in T5 (E1 to E3; r = -0.705), KE nondominant leg (KEND; E2 to E3; r = 0.786), and KF (E3 to E4; r = 0.575-0.590). The interrelationship between muscle strength (e.g., KE), sprint (e.g., T5), and jump abilities (CMJ) suggests the importance of muscle strength and power training for soccer. This study suggests that the systematic participation of the players in soccer matches favors the increase and maintenance of soccer players KE and KF muscle strength and sprint ability (T5). Thus, given the unique demands of actual match play, coaches should try to incorporate a competitive friendly match in the weekly training cycle of nonstarter players.

The maximal and sub-maximal versions of the Yo-Yo intermittent endurance test level 2 are simply reproducible, sensitive and valid

We appreciate Drs. Mendez-Villanueva and Buchheit’s interest in our work (Bradley et al. 2011b) and agree that the relationship between physical capacity and match performance of soccer players is complex. However, there are several flaws in their critique of our study (MendezVillanueva and Buchheit 2011) and some of them need to be corrected as a matter of record. The first point raised by the Letter makes the assertion that our article incorrectly concludes that the Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2) is a valid assessment tool for elite soccer populations. Although no exact measure of physical performance in elite soccer matches exists, the total distance and that covered at high-intensity provide useful indicators (Mohr et al. 2003). We observed a significant correlation between the Yo-Yo IE2 test performance and both total distance (r = 0.74, P \ 0.01) and high-intensity running during a game (r = 0.58, P \ 0.05). At this point, it is worth reminding the authors of the Letter that the strength of the correlations are large to very large, based on the classifications of Cohen (1988) and Hopkins et al. (2009). Thus, it is unclear why Drs. Mendez-Villanueva and Buchheit suggest that this conclusion is erroneous, especially given that their research group has recently based inferences on similar correlation strengths (Mendez-Villanueva et al. 2011). The lower correlation observed for high-intensity running is hardly surprising given that this variable can differ substantially from game to game (Gregson et al. 2010). However, we make reference to this point in the Discussion. Recently, we observed a stronger correlation between Yo-Yo IE2 test performance and high-intensity running (r = 0.67, P \ 0.01) using a larger number of elite players over multiple games (Bradley et al. unpublished data). Another interesting finding from this study was a correlation between the changes in Yo-Yo IE2 test performance and the change in high-intensity running during match-play across the season, whereas this was not evident for maximal oxygen uptake ( _ VO2 max). In further support of the validity of the Yo-Yo IE2 test, other studies have found correlations between Yo-Yo IE2 test performance and high-intensity running during a match for elite futsal referees (r = 0.77, P \ 0.05; Rebelo et al. 2011) and the fatigue index exhibited by elite female soccer players during repeated sprinting (r = 0.76, P \ 0.05; Krustrup et al. 2010). We also refute the assumption that we make inferences in our article about ‘predicting’ match performance from Yo-Yo IE2 test performance. This interpretation is not only a distortion of our findings but also an error of fact as we did not make this suggestion anywhere in the article. However, we do correctly identify that, due to the scattered trend exhibited by the correlation between Yo-Yo IE2 test performance and _ VO2 max, it would be erroneous to predict performance in one variable using the other. We particularly made reference to the test’s lack of predictive ability for _ VO2max rather than high-intensity running, given that this is a common question Communicated by Susan A. Ward.