Yo-Yo Intermittent Recovery Test Level Research Articles

Ergogenic effects of caffeine and sodium bicarbonate supplementation on intermittent exercise performance preceded by intense arm cranking exercise

BackgroundCaffeine and sodium bicarbonate ingestion have been suggested to improve high-intensity intermittent exercise, but it is unclear if these ergogenic substances affect performance under provoked metabolic acidification. To study the effects of caffeine and sodium bicarbonate on intense intermittent exercise performance and metabolic markers under exercise-induced acidification, intense arm-cranking exercise was performed prior to intense intermittent running after intake of placebo, caffeine and sodium bicarbonate.MethodsMale team-sports athletes (n = 12) ingested sodium bicarbonate (NaHCO3; 0.4 g.kg−1 b.w.), caffeine (CAF; 6 mg.kg−1 b.w.) or placebo (PLA) on three different occasions. Thereafter, participants engaged in intense arm exercise prior to the Yo-Yo intermittent recovery test level-2 (Yo-Yo IR2). Heart rate, blood lactate and glucose as well as rating of perceived exertion (RPE) were determined during the protocol.ResultsCAF and NaHCO3 elicited a 14 and 23% improvement (P < 0.05), respectively, in Yo-Yo IR2 performance, post arm exercise compared to PLA. The NaHCO3 trial displayed higher [blood lactate] (P < 0.05) compared to CAF and PLA (10.5 ± 1.9 vs. 8.8 ± 1.7 and 7.7 ± 2.0 mmol.L−1, respectively) after the Yo-Yo IR2. At exhaustion CAF demonstrated higher (P < 0.05) [blood glucose] compared to PLA and NaHCO3 (5.5 ± 0.7 vs. 4.2 ± 0.9 vs. 4.1 ± 0.9 mmol.L−1, respectively). RPE was lower (P < 0.05) during the Yo-Yo IR2 test in the NaHCO3 trial in comparison to CAF and PLA, while no difference in heart rate was observed between trials.ConclusionsCaffeine and sodium bicarbonate administration improved Yo-Yo IR2 performance and lowered perceived exertion after intense arm cranking exercise, with greater overall effects of sodium bicarbonate intake.

The Effect of Two Speed Endurance Training Regimes on Performance of Soccer Players.

In order to better understand the specificity of training adaptations, we compared the effects of two different anaerobic training regimes on various types of soccer-related exercise performances. During the last 3 weeks of the competitive season, thirteen young male professional soccer players (age 18.5±1 yr, height 179.5±6.5 cm, body mass 74.3±6.5 kg) reduced the training volume by ~20% and replaced their habitual fitness conditioning work with either speed endurance production (SEP; n = 6) or speed endurance maintenance (SEM; n = 7) training, three times per wk. SEP training consisted of 6–8 reps of 20-s all-out running bouts followed by 2 min of passive recovery, whereas SEM training was characterized by 6–8 x 20-s all-out efforts interspersed with 40 s of passive recovery. SEP training reduced (p<0.01) the total time in a repeated sprint ability test (RSAt) by 2.5%. SEM training improved the 200-m sprint performance (from 26.59±0.70 to 26.02±0.62 s, p<0.01) and had a likely beneficial impact on the percentage decrement score of the RSA test (from 4.07±1.28 to 3.55±1.01%) but induced a very likely impairment in RSAt (from 83.81±2.37 to 84.65±2.27 s). The distance covered in the Yo-Yo Intermittent Recovery test level 2 was 10.1% (p<0.001) and 3.8% (p<0.05) higher after SEP and SEM training, respectively, with possibly greater improvements following SEP compared to SEM. No differences were observed in the 20- and 40-m sprint performances. In conclusion, these two training strategies target different determinants of soccer-related physical performance. SEP improved repeated sprint and high-intensity intermittent exercise performance, whereas SEM increased muscles’ ability to maximize fatigue tolerance and maintain speed development during both repeated all-out and continuous short-duration maximal exercises. These results provide new insight into the precise nature of a stimulus necessary to improve specific types of athletic performance in trained young soccer players.

Anthropometric and Physical Profiles of English Academy Rugby Union Players.

The purpose of this study was to evaluate the anthropometric and physical characteristics of English regional academy rugby union players by age category (under 16s, under 18s and under 21s). Data were collected on 67 academy players at the beginning of the preseason period and comprised anthropometric (height, body mass, and sum of 8 skinfolds) and physical (5-, 10-, 20-, and 40-m sprint, acceleration, velocity, and momentum; agility 505; vertical jump; Yo-Yo intermittent recovery test level 1; 30-15 intermittent fitness test; absolute and relative 3 repetition maximum front squat, split squat, bench press, prone row, and chin; and isometric mid-thigh pull). One-way analysis of variance demonstrated significant increases across the 3 age categories (p ≤ 0.05) for height (e.g., 16s = 178.8 ± 7.1; 18s = 183.5 ± 7.2; 21s = 186.7 ± 6.61 cm), body mass (e.g., 16s = 79.4 ± 12.8; 18s = 88.3 ± 11.9; 21s = 98.3 ± 10.4 kg), countermovement jump height and peak power, sprint momentum, velocity, and acceleration; absolute, relative, and isometric (e.g., 16s = 2,157.9 ± 309.9; 18s = 2,561.3 ± 339.4; 21s = 3,104.5 ± 354.0 N) strength. Momentum, maximal speed, and the ability to maintain acceleration were all discriminating factors between age categories, suggesting that these variables may be more important to monitor rather than sprint times. These findings highlight that anthropometric and physical characteristics develop across age categories and provide comparative data for English Academy Rugby Union players.

Efek minuman kombinasi maltodekstrin dan vitamin C terhadap VO2maks atlet sepak bola

Background: VO2max is one of win determiner in a game. Athletes receive training to improve technical skills, tactical skills, and physiology functions that can support the improvement of VO2max, so they can improve their achievement. Maltodextrin and vitamin C can be used as an ingredient for beverage products which can improve VO2max.Objective: To assess the effect of maltodextrin and vitamin C combination drink on VO2max in soccer athletes.Method: Type of this study was experimental design with the same subject design. The study was conducted from January 2014 until June 2014 at Culinary Laboratory Universitas Gadjah Mada (UGM) and Stadium of Universitas Negeri Yogyakarta (UNY). Subjects of this study were 14 soccer players coming from Universitas Negeri Yogyakarta (UNY). Every subject had to fulfill the inclusion and exclusion criteria, and the subjects were chosen by purposive sampling. In the first treatment, subjects received the combination drink―a drink with a composition 15% of maltodextrin and 250 mg of vitamin C in 300 mL. After 6 days washout period, subjects received 300 mL plain water. Drinks were given 30 minutes before VO2max test. VO2max test method used in this study was yo-yo intermittent recovery test level 2 (IR-2).Results: VO2max when subjects consumed maltodextrin and vitamin C combination drink was significantly lower than VO2max when athletes consumed plain water (p=0,0000).Conclusion: Maltodextrin and vitamin C combination drink was less effective than plain water to enhance VO2max.

Acute effects of Yo-Yo intermittent recovery test level 1 (Yo-YoIR1) on hemorheological parameters in female volleyball players.

In the present study, we investigated possible alterations in red blood cell (RBC) deformability, plasma and whole blood viscosities (WBV) and hematological parameters in response to Yo-Yo intermittent recovery test level 1 (Yo-YoIR1) which is currently used to assess endurance performance, in female volleyball players. Eight volleyball player volunteers from Pamukkale University (mean age19,9 ± 2,2 years; mean body height 177.5 ± 1.99 cm; mean body mass index 21.66 ± 0.64 kg/m2) participated to the study. Blood samples were collected before and immediately after test. Red blood cell (RBC) deformability was determined by ektacytometer, plasma and whole blood viscosities (WBV) by a cone-plate rotational viscometer. Hematological parameters were determined using an electronic hematology analyzer. The Yo-YoIR1 applied, induced acute increments in WBV at native hematocrit (Hct) measured at a shear rate of 150 s-1 and 375 s-1, RBC deformability and WBC count. The results of the current study indicate that, the Yo-Yo IR1 test used to determine physical capacity of the player, by resulting in increments in RBC deformability contributes blood flow and thus, athletic performance of the individual.

Comparison of Two Kinds of Endurance Training Programs on the Effects of the Ability to Recover in Amateur Soccer Players.

Background:High intensity intermittent aerobic exercise is an elementary endurance training exercise to build soccer endurance. Many studies exist with professional soccer players. But limited research has been conducted with amateur soccer players.Objectives:The aim of this study was to compare and assess the effects of the shuttle-run method and the Hoff-track method on the ability to recover in amateur soccer players within three weeks.Patients and Methods:Two amateur soccer teams were randomly assigned to shuttle-run group (n = 24; SRG) (SRG: shuttle-run group) or Hoff-track group (n = 18; HTG) (HTG: hoff-track group). They performed 2 times/week over three weeks their program. SRG performed a 20 m high speed shuttle-run until exhaustion and HTG covered at their highest speed level an obstacle track. Before and after training the yo-yo intermittent recovery test level 2 (YYIRTL2) was conducted.Results:Significant differences were observed within (P < 0.05) and between the groups (P = 0.06; ES = 0.50) in distance covering during YYIRTL2.Conclusions:Both training methods seem to improve the ability to recover in amateur soccer players within a short time period during the competition season.

Longitudinal development of anthropometric and physical characteristics within academy rugby league players.

The purpose of this study was to evaluate the annual and long-term (i.e., 4 years) development of anthropometric and physical characteristics in academy (16-20 years) rugby league players. Players were assessed at the start of preseason over a 6-year period and were required to be assessed on consecutive years to be included in the study (Under 16-17, n = 35; Under 17-18, n = 44; Under 18-19, n = 35; Under 19-20, n = 16). A subset of 15 players were assessed for long-term changes over 4 years (Under 16-19). Anthropometric (height, body mass, sum of 4 skinfolds) and physical (10- and 20-m sprint, 10-m momentum, vertical jump, yo-yo intermittent recovery test level 1, 1 repetition maximum [1RM] squat, bench press, and prone row) assessments were collected. Paired t-tests and repeated measures analysis of variance demonstrated significant annual (e.g., body mass, U16 = 76.4 ± 8.4, U17 = 81.3 ± 8.3 kg; p < 0.001, d = 0.59) and long-term (e.g., vertical jump, Under 16 = 44.1 ± 3.8, Under 19 = 52.1 ± 5.3 cm; p < 0.001, d = 1.74) changes in anthropometric and physical characteristics. Greater percentage changes were identified between the Under 16-17 age categories compared with the other ages (e.g., 1RM squat, U16-17 = 22.5 ± 19.5 vs. U18-19 = 4.8 ± 6.4%). Findings demonstrate the annual and long-term development of anthropometric and physical characteristics in academy rugby league players establishing greater changes occur at younger ages upon the commencement of a structured training program within an academy. Coaches should understand the long-term development of physical characteristics and use longitudinal methods for monitoring and evaluating player performance and development.

External Responsiveness of the Yo-Yo IR Test Level 1 in High-level Male Soccer Players.

The aim of this study was to assess the external responsiveness, construct validity and internal responsiveness of the Yo-Yo Intermittent Recovery test level 1 and its sub-maximal version in semi-professional players. Tests and friendly matches were performed during the preseason and regular season. The distance covered above 15 km·h(-1) was considered as an indicator of the physical match performance. Construct validity and external responsiveness were examined by correlations between test and physical match performance (preseason and regular season) and training-induced changes. Internal responsiveness was determined as Cohen's effect size, standardized response mean and signal-to-noise ratio. The physical match performance increased after training (34.8%). The Yo-Yo Intermittent Recovery test level 1 improved after training (40.2%), showed longitudinal (r=0.69) and construct validity (r=0.73 and 0.59, preseason and regular season) and had higher internal responsiveness compared to its sub-maximal version. The heart rate at the 6(th) minute in the sub-maximal version did not show longitudinal (r=-0.38) and construct validity (r=0.01 and -0.06, preseason and regular season) and did not significantly change after training (-0.3%). The rate of perceived exertion decreased in the sub-maximal version (- 29.8%). In conclusion, the Yo-Yo Intermittent Recovery test level 1 is valid and responsive, while the validity of its sub-maximal version is questionable.

Team-Sport Athletes' Improvement of Performance on the Yo-Yo Intermittent Recovery Test Level 2, but Not of Time-Trial Performance, With Intermittent Hypoxic Training.

To determine the time course for physical-capacity adaptations to intermittent hypoxic training (IHT) in team-sport athletes and the time course for benefits remaining after IHT. A pre-post parallel-groups design was employed, with 21 Australian footballers assigned to IHT (n = 10) or control (CON; n = 11) matched for training load. IHT performed eleven 40-min bike sessions at 2500-m altitude over 4 wk. Yo-Yo Intermittent Recovery Test level 2 (Yo-Yo IR2) was performed before; after 3, 6, and 11 IHT sessions; and 30 and 44 d after IHT. Repeated time trials (2- and 1-km TTs, with 5 min rest) were performed before, after, and 3 wk after IHT. Hemoglobin mass (Hb(mass)) was measured in IHT before and after 3, 6, 9, and 11 sessions. Baseline Yo-Yo IR2 was similar between groups. After 6 sessions, the change in Yo-Yo IR2 in IHT was very likely higher than CON (27% greater change, effect size 0.77, 90% confidence limits 0.20;1.33) and likely higher 1 d after IHT (23%, 0.68, 0.05;1.30). The IHT group's change remained likely higher than CON 30 d after IHT (24%, 0.72, 0.12;1.33) but was not meaningfully different 44 d after (12%, 0.36, -0.24;0.97). The change in 2-km TT performance between groups was not different throughout. For 1-km TT, CON improved more after IHT, but IHT maintained performance better after 3 wk. Hb(mass) was higher after IHT (2.7%, 0.40, -0.40;1.19). Short-duration IHT increased Yo-Yo IR2 compared with training-load-matched controls in 2 wk. An additional 2 wk of IHT provided no further benefit. These changes remained until at least 30 d posttraining. IHT also protected improvement in 1-km TT.

Comparison of the Physiological Responses and Time-Motion Characteristics of Young Soccer Players in Small-Sided Games

The purpose of this study was to investigate the effect of "with goalkeeper" (SSGwith) and "without goalkeeper" (SSGwithout) conditions on players' physiological responses and time-motion characteristics in small-sided games. Sixteen young soccer players (age: 16.5 ± 1.5 years; height: 175.5 ± 5.2 cm; body mass: 63.0 ± 6.9 kg; training experience: 6.3 ± 1.3 years) participated in 2 different 2-a-side, 3-a-side, and 4-a-side games: SSGwith and SSGwithout. The players underwent anthropometric measurements (height and body mass) followed by the Yo-Yo intermittent recovery test (level 1). Then they played 2-a-side, 3-a-side, and 4-a-side SSGwith and SSGwithout soccer-specific SSGs in random order at 2-day intervals. Heart rate (HR) responses and distance covered in different speed zones (walking [WLK, 0-6.9 km·h(-1)], low-intensity running [LIR, 7.0-12.9 km·h(-1)], moderate-intensity running [MIR, 13.0-17.9 km·h(-1)], and high-intensity running [HIR, >18 km·h(-1)]) were measured during the SSGs, whereas the rating of perceived exertion (RPE) and blood lactate (La) were determined at the end of the last bout of each SSG. During the SSGwithout players showed higher %HR, La, and RPE (p ≤ 0.05), greater distance covered in LIR, MIR, HIR, and total distance (p ≤ 0.05) compared with the SSGwith during the 2-a-side, 3-a-side, and 4-a-side games. The results of this study suggest that both SSGwith and SSGwithout could be used for the physiological adaptations required for soccer-specific aerobic endurance. However, if coaches want both higher physiological responses and greater distance covered in the intensity running zone from their teams, SSGwithout should be organized. In addition, this study also suggests that smaller format games (i.e., 2-a-side) may promote some anaerobic adaptations for youth soccer players.

The Influence of Physical Fitness and Playing Standard on Pacing Strategies During a Team-Sport Tournament.

To assess the influence of playing standard and physical fitness on pacing strategies during a junior team-sport tournament. A between-groups, repeated-measures design was used. Twenty-eight junior team-sport players (age 16.6 ± 0.5 y, body mass 79.9 ± 12.0 kg) from a high-standard and low-standard team participated in a junior rugby league tournament, competing in 5 games over 4 d (4 × 40-min and 1 × 50-min game). Players wore global positioning system (GPS) microtechnology during each game to provide information on match activity profiles. The Yo-Yo Intermittent Recovery Test (level 1) was used to assess physical fitness before the competition. High-standard players had an initially higher pacing strategy than the low-standard players, covering greater distances at high (ES = 1.32) and moderate speed (ES = 1.41) in game 1 and moderate speed (ES = 1.55) in game 2. However, low-standard players increased their playing intensity across the competition (ES = 0.57-2.04). High-standard/high-fitness players maintained a similar playing intensity, whereas high-standard/low-fitness players reduced their playing intensities across the competition. Well-developed physical fitness allows for a higher-intensity pacing strategy that can be maintained throughout a tournament. High-standard/low-fitness players reduce playing intensity, most likely due to increased levels of fatigue as the competition progresses. Low-standard players adopt a pacing strategy that allows them to conserve energy to produce an "end spurt" in the latter games. Maximizing endurance fitness across an entire playing group will maximize playing intensity and minimize performance reductions during the latter stages of a tournament.

Relationships between the yo-yo intermittent recovery test and anaerobic performance tests in adolescent handball players.

The aim of the present study was to investigate relationships between a performance index derived from the Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1) and other measures of physical performance and skill in handball players. The other measures considered included peak muscular power of the lower limbs (Wpeak), jumping ability (squat and counter-movement jumps (SJ, CMJ), a handball skill test and the average sprinting velocities over the first step (VS) and the first 5 m (V5m). Test scores for 25 male national-level adolescent players (age: 17.2 ± 0.7 years) averaged 4.83 ± 0.34 m·s−1 (maximal velocity reached at the Yo-Yo IR1); 917 ± 105 Watt, 12.7 ± 3 W·kg−1 (Wpeak); 3.41 ± 0.5 m·s−1 and 6.03 ± 0.6 m·s−1 (sprint velocities for Vs and V5m respectively) and 10.3 ± 1 s (handball skill test). Yo-Yo IR1 test scores showed statistically significant correlations with all of the variables examined: Wpeak (W and W·kg−1) r = 0.80 and 0.65, respectively, p≤0.001); sprinting velocities (r = 0.73 and 0.71 for VS and V5m respectively; p≤0.001); jumping performance (SJ: r = 0.60, p≤0.001; CMJ: r= 0.66, p≤0.001) and the handball skill test (r = 0.71; p≤0.001). We concluded that the Yo-Yo test score showed a sufficient correlation with other potential means of assessing handball players, and that intra-individual changes of Yo-Yo IR1 score could provide a useful composite index of the response to training or rehabilitation, although correlations lack sufficient precision to help in players’ selection.

The relationship between physical capacity and match running performance in men’s tag football

This study examined the differences in match-activity profiles between selected and non-selected representative players and determined the relationship between Yo-Yo intermittent recovery test level 2 (Yo-Yo IR2) and match running performance in tag football. The match-activity profiles of fifteen male tag football players from the same team were determined using global positioning system (GPS) devices during the 2014 Queensland State Cup. Differences were examined based on representative selection into the Queensland state team and the relationship between Yo-Yo IR2 and match running performance was assessed using partial correlations controlling for playing position. Selected representative players covered greater distances during the Yo-Yo IR2 compared to non-selected players (ES=1.40; p<0.01). Selected players also covered greater distances at very high-intensity (VHIA) running (ES=0.65; p<0.01), performed more frequent VHIA efforts (ES=0.61; p<0.01) and reached higher peak running speeds (ES=0.51; p=0.01) during matches. Yo-Yo IR2 performance had a positive association with VHIA distance (r=.77; p<0.01), VHIA effort frequency (r=.75; p<0.01) and peak running speed (r=.77; p<0.01). The Yo-Yo IR2 is a useful determinant of high-intensity running performance and appears to influence playing ability in men’s tag football. Improving the physical capacities related to the Yo-Yo IR2 should be a key focus of training programs for tag football players competing at state-level competition.

Anthropometric and physical performance characteristics of top-elite, elite and non-elite youth female team handball players

In order to maximise the potential for success, developing nations need to produce superior systems to identify and develop talent, which requires comprehensive and up-to-date values on elite players. This study examined the anthropometric and physical characteristics of youth female team handball players (16.07 ± 1.30 years) in non-elite (n = 47), elite (n = 37) and top-elite players (n = 29). Anthropometric profiling included sum of eight skinfolds, body mass, stature, girths, breadths and somatotype. Performance tests included 20 m sprint, counter-movement jump, throwing velocity, repeated shuttle sprint and jump ability test, and Yo-Yo Intermittent Recovery Test Level 1. Youth top-elite players had greater body mass, lean mass, stature, limb girths and breadths than elite and non-elite players, while only stature and flexed arm were higher in elite compared to non-elite players (all P < 0.05). Sum of skinfolds and waist-to-hip ratio were similar between groups (P > 0.05). Top-elite performed better in most performance tests compared to both elite and non-elite players (P < 0.05), although maximal and repeated 10 m sprints were similar between playing standards (P > 0.05). Elite outperformed non-elite players only in throwing velocity. The findings reveal that non-elite players compare unfavourably to top-elite international European players in many anthropometric and performance characteristics, and differ in a few characteristics compared to elite European club team players. This study is useful for emerging team handball nations in improving talent identification processes.

The effects of sodium bicarbonate supplementation on asoccer specific conditioning test in division III soccer players

Objectives: This study investigated the performance enhancing effects of bicarbonate ingestion on soccer specific performance. Design: A randomized and double-blinded study. Methods: Division III collegiate male soccer players (N = 7) participated in the study. Participants ingested either an alkaline treatment (.3 g/kg NaHCO3) or placebo (cornflower) 60 min prior to exercise on two separate testing sessions spaced 7 days apart. Distance to fatigue in the Yo-Yo Intermittent Recovery Test Level 2 was used to assess performance. Capillary blood was sampled pre-ingestion (PE), 60 min post ingestion (PI), exhaustion (EX), following 15 min of recovery (RC) and analyzed for lactate ([La–]) and pH. Results: No significant ( p > .05) differences between conditions existed for performance. A significant ( p .05) existed between time and condition. pH values at PE and PI were significantly greater than EX and RC in both conditions; however, pH was significantly ( p < .05) greater at PI than PE in treatment but not placebo. Conclusion: Bicarbonate ingestion increased extracellular buffering capacity but does not appear to enhance shuttle run performance in Division III soccer players. (Journal of Trainology 2015;4:19-24)

Caffeine supplementation does not affect match activities and fatigue resistance during match play in young football players

The study examined the effect of caffeine supplementation on match activities and development of fatigue during a football match. In a randomised, double-blind cross-over design, two experimental football games separated by 7 days were organised between the junior teams of two professional football clubs (17.6 ± 1.1 years (±s), 71.7 ± 6.9 kg, 13.9% ± 5.0% body fat). The players ingested either a capsule of 6 mg · kg−1 b.w. caffeine or placebo (dextrose) 65 min prior to the matches. Match activities were assessed using the ZXY match analysis system, and a Yo-Yo intermittent recovery test–level 2 (Yo-Yo IR2) was conducted immediately post-game. Heart rate was monitored throughout the game, and blood samples were obtained at baseline, half-time and after the game. There were no differences between caffeine and placebo regarding total distance covered (10,062 ± 916 vs 9854 ± 901 m), high-intensity running (557 ± 178 vs 642 ± 240 m), sprinting distance (109 ± 58 vs 112 ± 69 m) or acceleration counts (123 ± 31 vs 126 ± 24). In both trials, players displayed lower (P < 0.05) values in total distance and acceleration counts in the last 15 min compared to all other 15-min periods of the matches. Post-game Yo-Yo IR2 performance was not different between game trials (caffeine: 829 ± 322 m; placebo 819 ± 289 m). In conclusion, oral caffeine administration does not appear to have an ergogenic effect in young football players during match play.

Are the Yo-Yo intermittent recovery test levels 1 and 2 both useful? Reliability, responsiveness and interchangeability in young soccer players

The aim of this study was to compare the reliability, internal responsiveness and interchangeability of the Yo-Yo intermittent recovery test level 1 (YY1), level 2 (YY2) and submaximal YY1 (YY1-sub). Twenty-four young soccer players (age 17 ± 1 years; height 177 ± 7 cm; body mass 68 ± 6 kg) completed each test five times within pre- and in-season; distances covered and heart rates (HRs) were measured. Reliability was expressed as typical error of measurement (TEM) and intraclass correlation coefficient (ICC). Internal responsiveness was determined as effect size (ES) and signal-to-noise ratio (ESTEM). Interchangeability was determined with correlation between training-induced changes. The TEM and ICC for distances in the YY1 and YY2 and for HR in YY1-sub were 7.3% and 0.78, 7.1% and 0.93 and 2.2% and 0.78, respectively. The ESs and ESTEMs were 0.9 and 1.9 for YY1, 0.4 and 1.2 for YY2 and −0.3 and −0.3 for YY1-sub. Correlations between YY1 vs. YY2 and YY1-sub were 0.56 to 0.84 and −0.36 to −0.81, respectively. Correlations between change scores in YY1 vs. YY2 were 0.29 and −0.21 vs. YY1-sub. Peak HR was higher in YY1 vs. YY2. The YY1 and YY2 showed similar reliability; however, they were not interchangeable. The YY1 was more responsive to training compared to YY2 and YY1-sub.

The Yo-Yo intermittent recovery test level 1 is reliable in young high-level soccer players.

The aim of the study was to investigate test reliability of the Yo-Yo intermittent recovery test level 1 (YYIR1) in 36 high-level youth soccer players, aged between 13 and 18 years. Players were divided into three age groups (U15, U17 and U19) and completed three YYIR1 in three consecutive weeks. Pairwise comparisons were used to investigate test reliability (for distances and heart rate responses) using technical error (TE), coefficient of variation (CV), intra-class correlation (ICC) and limits of agreement (LOA) with Bland-Altman plots. The mean YYIR1 distances for the U15, U17 and U19 groups were 2024 ± 470 m, 2404 ± 347 m and 2547 ± 337 m, respectively. The results revealed that the TEs varied between 74 and 172 m, CVs between 3.0 and 7.5%, and ICCs between 0.87 and 0.95 across all age groups for the YYIR1 distance. For heart rate responses, the TEs varied between 1 and 6 bpm, CVs between 0.7 and 4.8%, and ICCs between 0.73 and 0.97. The small ratio LOA revealed that any two YYIR1 performances in one week will not differ by more than 9 to 28% due to measurement error. In summary, the YYIR1 performance and the physiological responses have proven to be highly reliable in a sample of Belgian high-level youth soccer players, aged between 13 and 18 years. The demonstrated high level of intermittent endurance capacity in all age groups may be used for comparison of other prospective young soccer players.

Effects of Additional Repeated Sprint Training During Preseason on Performance, Heart Rate Variability, and Stress Symptoms in Futsal Players

The aim of this study was to investigate whether supplementing regular preseason futsal training with weekly sessions of repeated sprints (RS) training would have positive effects on repeated sprint ability (RSA) and field test performance. Thirteen players from a professional futsal team (22.6 ± 6.7 years, 72.8 ± 8.7 kg, 173.2 ± 6.2 cm) were divided randomly into 2 groups (AddT: n = 6 and normal training group: n = 7). Both groups performed a RSA test, Yo-Yo intermittent recovery test level 1 (YoYo IR1), squat (SJ) and countermovement jumps (CMJ), body composition, and heart rate variability (HRV) measures at rest before and after 4 weeks of preseason training. Athletes weekly stress symptoms were recorded by psychometric responses using the Daily Analysis of Life Demands for Athletes questionnaire and subjective ratings of well-being scale, respectively. The daily training load (arbitrary units) was assessed using the session of rating perceived exertion method. After the preseason training, there were no significant changes for body composition, SJ, CMJ, and RSAbest. The YoYo IR1, RSAmean, RSAworst, and RSAdecreament were significantly improved for both groups (p ≤ 0.05). The HRV parameters improved significantly within both groups (p ≤ 0.05) except for high frequency (HF, absolute and normalized units, [n.u.]), low frequency (LF) (n.u.), and the LF/HF ratio. A moderate effect size for the AddT group was observed for resting heart rate and several HRV measures. Training load and psychometric responses were similar between both groups. Additional RS training resulted in slightly greater positive changes for vagal-related HRV with similar improvements in performance and training stress during the preseason training in futsal players.

Effects of two types of partial sleep deprivation on hematological responses during intermittent exercise: A pilot study

Summary Objective To examine the effects of two types of partial sleep deprivation (PSD) on hematological responses at rest and following an intermittent exercise performed in the evening with young athletes. Material and methods Ten Taekwondo players were randomized in three sleep conditions (baseline sleep night [BN], partial sleep deprivation at the beginning of night [PSDBN], partial sleep deprivation at the end of night [PSDEN]). Blood samples were collected during each condition, before and after a Yo-Yo intermittent recovery test level 1. Results At rest and in comparison with BN, there was a significant decrease in monocytes (P Conclusion PSD at the beginning and at the end of night could cause an immunosuppression without alteration in red blood cells family, plasma iron and platelets family during the intermittent exercise.