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1.
Abstract

The aims of the current study were to assess the development and determine the underlying mechanisms of sprinting and dribbling needed to compete at the highest level in youth soccer. Talented soccer players aged 12–19 years (n = 267) were measured on a yearly basis in a longitudinal study over 7 years, resulting in 519 measurements. Two field tests, the Shuttle Sprint and Dribble Test and the Slalom Sprint and Dribble Test, were assessed. Anthropometric characteristics, years of soccer experience, and duration of practice were recorded. The longitudinal data were analysed with multi-level modelling. Comparing the two tests at baseline, low correlations were observed (sprinting: r = 0.49; dribbling: r = 0.22), indicating that each test measures distinct qualities (acceleration vs. agility). Low-to-moderate correlations were found between dribbling and sprinting within each test (Shuttle Sprint and Dribble Test: r = 0.54; Slalom Sprint and Dribble Test: r = 0.38). Both dribbling and sprinting improved with age, especially from ages 12 to 14, but the tempo of development was different. From ages 14 to 16, sprinting improved rapidly in contrast to dribbling; this was especially evident on the Slalom Sprint and Dribble Test. In contrast, after age 16 dribbling improved considerably but sprinting hardly improved. Besides age, the factors that contribute to dribbling performance are lean body mass, hours of practice, and playing position.  相似文献   

2.
This study assessed whether a new, closed-skill dribbling or sprinting task could predict attacking performance in soccer. Twenty-five male players were recruited from the Londrina Junior Team Football Academy in Brazil and asked to either dribble the ball or sprint through five custom circuits that varied in average curvature (0–1.37 radians.m?1). These measures were then validated using a realistic one vs. one competition in which each player acted as attacker or defender in turn (N = 1330 bouts). Sprinting (ICC = 0.96) and dribbling (ICC = 0.97) performances were highly repeatable for individual players. Average dribbling speed decreased non-linearly with increasing circuit curvature (F = 239.5; P < 0.001) from 5.19 ± 0.11 ms?1 on the straightest path to 2.13 ± 0.03 ms?1 on the curviest. Overall, dribbling but not sprinting performance predicted attacking success in the one vs. one competition, explaining more than 50% of the variation in attacking success alone (rp = 0.70; P < 0.001). In conclusion, our new closed-skill dribbling assessment is a valid and reliable protocol to predict a soccer player’s success in attacking performance in one vs. one situation, and can be used to identify talented players.  相似文献   

3.
Resisted sprint training consists of performing overloaded sprints, which may produce greater effects than traditional sprint training. We compared a resisted sprint training with overload control versus an unresisted sprint training program on performance in soccer players. Eighteen elite athletes were randomly assigned to resisted (RST) or unresisted sprint training protocol (UR). Before and after a 6-week training period, sprinting ability, change of direction speed (COD), vertical jumps (SJ and CMJ), mean power (MP) and mean propulsive power (MPP) at distinct loads were assessed. Both groups improved sprinting ability at all distances evaluated (5m: UR = 8%, RST = 7%; 10m: UR = 5%, RST = 5%; 15m: UR = 4%, RST = 4%; 20m: UR = 3%, RST = 3%; 25m: UR = 2%, RST = 3%;), COD (UR = 6%; RST = 6%), SJ (UR = 15%; RST = 13%) and CMJ (UR = 15%; RST = 15%). Additionally, both groups increased MP and MPP at all loads evaluated. The between-group magnitude-based inference analysis demonstrated comparable improvement (“trivial” effect) in all variables tested. Finally, our findings support the effectiveness of a short-term training program involving squat jump exercise plus sprinting exercises to improve the performance of soccer players.  相似文献   

4.
ABSTRACT

The speed performance is involved not only in linear sprints, but also in a wide spectrum of multi-directional movements, such as curve sprinting. Curved sprint can be defined as sprint with gradual and continuous change of direction (COD). Although ~85% of the actions performed at maximum velocity in a professional soccer league are curvilinear sprints, there is not any specific test to assess this ability. This study aimed to analyse the reliability of a new curve sprint test, and compare its results with those obtained by soccer players in linear sprint. Forty experienced soccer players performed 3 attempts of curve sprint (using the penalty arc) to right and left side (17 m), and 3 linear sprints (17 m) in two different days. The ICCs (inter-session reliability) were 0.93 for sprint curve right side (CSRS) and 0.89 for sprint curve left side (CSLS), considered “acceptable”. The CVs (intra-session reliability) were 0.87% in CSRS and 1.15% in CSLS. The coefficient of determination (R2) between linear and curve sprinting was ~35%. The association between curve sides was “very large” (r = 0.878; p < 0.01). In summary, we showed that “curve sprint test” is highly reliable, and that curvilinear and linear sprints are different and independent actions.  相似文献   

5.
The purpose of this study was to assess the effect of periodized resistance training on accelerative sprint performance. Sixteen physically active men participated in a randomized controlled study. An experimental group (n = 10) completed an 8-week periodized resistance training intervention, while a control group (n = 6) did not train. Pre- and post-training measures of 20-m straight-line sprint time, including a 10-m split, maximum strength, and explosive strength, were recorded. Flight time, stance time, stride length, and stride frequency were quantified from digitized video recordings of the first three strides of the 20-m sprint. Resistance training resulted in significant increases in maximum strength (parallel back squat: 19%) and explosive strength (6–10%). However, both groups increased 0–10 m sprint times (experimental group = 6%; control group = 3%) while 10–20 m times were reduced (experimental group = 7%; control group = 4%), highlighting the mechanical differences between the distinct sprint phases. The change during the 0–10 m interval was accompanied by a reduction in stride frequency during the first three strides. Strength coaches should be aware that the potential benefits of increased muscular strength during short sprints are likely to be affected by mechanical specificity and that improvements in sprinting performance may not occur immediately after a period of resistance training.  相似文献   

6.
Abstract

The aim of this study was to determine sprint profiles of professional female soccer players and evaluate how various speed thresholds impact those outcomes. Seventy-one professional players competing in full matches were assessed repeatedly during 12 regular season matches using a Global Positioning System (GPS). Locomotion ≥18 km · h?1 was defined as sprinting and each event was classified into: Zone 1: 18.0–20.9 km· h?1; Zone 2: 21.0–22.9 km · h?1; Zone 3: 23.0–24.9 km · h?1 and Zone 4: >25 km · h?1. Outcomes included: duration (s), distance (m), maximum speed (km · h?1), duration since previous sprint (min) and proportion of total sprint distance. In total 5,019 events were analysed from 139 player-matches. Mean sprint duration, distance, maximum speed and time between sprints were 2.3 ± 1.5 s, 15.1 ± 9.4 m, 21.8 ± 2.3 km· h?1, and 2.5 ± 2.5 min, respectively. Mean sprint distances were 657 ± 157, 447 ± 185, and 545 ± 217 m for forwards, midfielders and defenders, respectively (P ≤ 0.046). Midfielders had shorter sprint duration (P = 0.023), distance (P ≤ 0.003) and maximum speed (P < 0.001), whereas forwards performed more sprints per match (43 ± 10) than midfielders (31 ± 11) and defenders (36 ± 12) (P ≤ 0.016). Forty-five percent, 29%, 15%, and 11% of sprints occurred in sprint Zones 1, 2, 3 and 4, respectively. This group of professional female soccer players covered 5.3 ± 2.0% of total distance ≥18 km · h?1 with positional differences and percent decrements distinct from other previously identified elite players. These data should guide the development of high intensity and sprint thresholds for elite-standard female soccer players.  相似文献   

7.
This investigation examined step-by-step kinematics of sprint running acceleration. Using a randomised counterbalanced approach, 37 female team handball players (age 17.8 ± 1.6 years, body mass 69.6 ± 9.1 kg, height 1.74 ± 0.06 m) performed resisted, assisted and unloaded 20-m sprints within a single session. 20-m sprint times and step velocity, as well as step length, step frequency, contact and flight times of each step were evaluated for each condition with a laser gun and an infrared mat. Almost all measured parameters were altered for each step under the resisted and assisted sprint conditions (η2 ≥ 0.28). The exception was step frequency, which did not differ between assisted and normal sprints. Contact time, flight time and step frequency at almost each step were different between ‘fast’ vs. ‘slow’ sub-groups (η2 ≥ 0.22). Nevertheless overall both groups responded similarly to the respective sprint conditions. No significant differences in step length were observed between groups for the respective condition. It is possible that continued exposure to assisted sprinting might allow the female team-sports players studied to adapt their coordination to the ‘over-speed’ condition and increase step frequency. It is notable that step-by-step kinematics in these sprints were easy to obtain using relatively inexpensive equipment with possibilities of direct feedback.  相似文献   

8.
Abstract

The aim of this study was to examine the effects of changes in maximal aerobic (MAS) and sprinting (MSS) speeds and the anaerobic reserve (ASR) on repeated-sprint performance. Two hundred and seventy highly-trained soccer players (14.5 ± 1.6 year) completed three times per season (over 5 years) a maximal incremental running test to approach MAS, a 40-m sprint with 10-m splits to assess MSS and a repeated-sprint test (10 × 30-m sprints), where best (RSb) and mean (RSm) sprint times, and percentage of speed decrement (%Dec) were calculated. ASR was calculated as MSS-MAS. While ?RSb were related to ?MSS and ?body mass (r2 = 0.42, 90%CL[0.34;0.49] for the overall multiple regression, n = 334), ?RSm was also correlated with ?MAS and ?sum of 7 skinfolds (r2 = 0.43 [0.35;0.50], n = 334). There was a small and positive association between ?%Dec and ?MAS (r2 = 0.02 [?0.07;0.11], n = 334). Substantial ?MSS and ?MAS had a predictive value of 70 and 55% for ?RSm, respectively. Finally, ?ASR per se was not predictive of ?RSm (Cohen’s = +0.8 to ?0.3 with increased ASR), but the greater magnitude of ?RSm improvement was observed when MSS, MAS and ASR increased together (0.8 vs. +0.4 with ASR increased vs. not, additionally to MSS and MAS). Low-cost field tests aimed at assessing maximal sprinting and aerobic speeds can be used to monitor ?RS performance.  相似文献   

9.
Abstract

The aim of this study was to assess the extent to which measures derived from the new FIFA referees’ fitness tests can be used to monitor a referee's match-related physical capacity. Match-analysis data were collected (Prozone®, Leeds, UK) from 17 soccer referees for 5.0 (s = 1.7) FA Premier League matches per referee during the first 4 months of the 2007–08 season. Physical match performance categories included total distance covered, high-intensity running distance (speed >5.5 m · s?1), and sprinting distance (>7.0 m · s?1). The two tests were a 6 × 40-m sprint test and a 150-m interval test. Heart rate demand was correlated with total match distance covered (r = ?0.70, P = 0.002) and high-intensity running (r = ?0.57, P = 0.018) in the interval test. The fastest 40-m sprint was related to total distance covered (r = ?0.69, P = 0.002), high-intensity running (r = ?0.76, P < 0.001), and sprinting distance (r = ?0.75, P = 0.001), while mean time for the 40-m sprints was related to total distance covered (r = ?0.70, P = 0.002), high-intensity running (r = ?0.77, P < 0.001), and sprinting distance (r = ?0.77, P < 0.001). The referees who recorded the best interval-test heart rate demand and fastest 40-m time produced the best physical match performances. However, only the sprint test and in particular the fastest 40-m time had appropriate construct validity for the physical assessment of soccer referees.  相似文献   

10.
Abstract

The present study aimed to analyse the influence of speed and power abilities in goal situations in professional football.

During the second half of the season 2007/08, videos of 360 goals in the first German national league were analysed by visual inspection. For the assisting and the scoring player the situations immediately preceding the goal were evaluated. The observed actions were categorised as: no powerful action, rotation (around the body's centre-line), straight sprint, change-in-direction sprint, jump, or a combination of those categories.

Two hundred and ninety-eight (83%) goals were preceded by at least one powerful action of the scoring or the assisting player. Most actions for the scoring player were straight sprints (n = 161, 45% of all analysed goals, P < 0.001) followed by jumps (n = 57, 16%), rotations and change-in-direction sprints (n = 22, 6% each). Most sprints were conducted without an opponent (n = 109, P < 0.001) and without the ball (n = 121, P < 0.001). Similarly, for the assisting player the most frequent action was a straight sprint (n = 137, P < 0.001) followed by rotations (n = 28), jumps (n = 22) and change-in-direction sprints (n = 18). The straight sprints were mostly conducted with the ball (n = 93, P = 0.003).

In conclusion, straight sprinting is the most frequent action in goal situations. Power and speed abilities are important within decisive situations in professional football and, thus, should be included in fitness testing and training.  相似文献   

11.
Abstract

The aim of this study was to test the hypothesis that sprint performance (time over a given distance) would be affected by track compliance, with better performances on the more compliant surface. Ten sprinters participated in the study. The athletes performed maximal sprints (60 m) on three different track configurations (hard, 5500 kN · m?1; soft, 2200 kN · m?1; spring, 550 kN · m?1). A 60-m single-lane running surface was constructed. Plywood boards (1.2 cm thick) were placed on a 60 × 0.6 m wooden chipboard frame serving as the base surface. All participants ran two times on each track configuration in a randomized order. The athletes' kinematics were recorded using the Vicon 624 system with 12 cameras operating at 250 Hz. Four Kistler force plates (1250 Hz) were used to record ground reaction forces. Sprint performance (time over 60 m) was unaffected by the different track compliances (P = 0.57). In addition, there was no effect of track (P > 0.05) on the sprinting kinematics and kinetics of the ankle or knee joint. The hypothesis that sprint performance is affected by track compliance can be rejected because the sprinters recorded similar performances while sprinting over 60 m on all three track configurations. We conclude that: (1) the possible deformation of the track while sprinting is minor enough not to cause a specific adjustment in the leg mechanics affecting the effectiveness of the stretch – shortening cycle of the sprinters; and (2) the energy exchange between sprinters and tracks has only a marginal effect on sprint performance due to its small magnitude. More research on tracks with lower stiffness is required.  相似文献   

12.
The purpose of this study was to determine the effectiveness of a 4-week running sprint interval training protocol to improve both aerobic and anaerobic fitness in middle-aged adults (40–50 years) as well as compare the adaptations to younger adults (20–30 years). Twenty-eight inactive participants – 14 young 20–30-year-olds (n = 7 males) and 14 middle-aged 40–50-year-olds (n = 5 males) – completed 4 weeks of running sprint interval training (4 to 6, 30-s “all-out” sprints on a curved, self-propelled treadmill separated by 4 min active recovery performed 3 times per week). Before and after training, all participants were assessed for maximal oxygen consumption (VO2max), 2000 m time trial performance, and anaerobic performance on a single 30-s sprint. There were no interactions between group and time for any tested variable, although training improved relative VO2max (young = 3.9, middle-aged = 5.2%; P < 0.04), time trial performance (young = 5.9, middle-aged = 8.2%; P < 0.001), peak sprint speed (young = 9.3, middle-aged = 2.2%; P < 0.001), and average sprint speed (young = 6.8, middle-aged = 11.6%; P < 0.001) in both young and middle-aged groups from pre- to post-training on the 30-s sprint test. The current study demonstrates that a 4-week running sprint interval training programme is equally effective at improving aerobic and anaerobic fitness in younger and middle-aged adults.  相似文献   

13.
The aim of this study was to evaluate the reliability of two long jump tasks and their ability to predict 10 m sprint performance in elite adolescent female athletes. Eight junior national-level female track and field athletes completed three standing (SLJ) and reactive long jumps (RLJ) on portable force plates, followed by three 10 m sprints. Intra-class correlation coefficients (ICC) and coefficients of variation (CV) were calculated to examine reliability. Linear regression results identified the best predictor of average and best 10 m sprint time from the jump kinematic and kinetic measures. The ICCs and CVs indicated good reliability for the majority of kinetic measures however, better reliability was reported for the SLJ. The SLJ was a good predictor of best and average 10 m sprint time, with average horizontal power the best predictor of performance (best; R 2 = 0.751, p = 0.003, Standard Error of Estimate (SEE)% = 2.2 average; R 2 = 0.708, p = 0.005, SEE% = 2.5).  相似文献   

14.
ABSTRACT

This study aimed to compare mechanical variables derived from torque-cadence and power-cadence profiles established from different cycle ergometer modes (isoinertial and isokinetic) and modelling procedures (second- and third-order polynomials), whilst employing a novel method to validate the theoretical maximal power output (Pmax). Nineteen well-trained cyclists (n = 12 males) completed two experimental sessions comprising six, 6-s maximal isoinertial or isokinetic cycling sprints. Maximal pedal strokes were extracted to construct power–cadence relationships using second- and third-order polynomials. A 6-s sprint at the optimal cadence (Fopt) or optimal resistance (Topt) was performed to assess construct validity of Pmax. No differences were found in the mechanical parameters when derived from isokinetic (Pmax = 1311 ± 415, Fopt = 118 ± 12) or isoinertial modes (Pmax = 1320 ± 421, Fopt = 116 ± 19). However, R2 improved (P < 0.02) when derived from isoinertial sprints. Third-order polynomial modelling improved goodness of fit values (Standard Error, adjusted R2), but derived similar mechanical parameters. Finally, peak power output during the optimised sprint did not significantly differ from the theoretical Pmax in both cycling modes, thus providing construct validity. The most accurate P-C profile can be derived from isoinertial cycling sprints, modelled using third-order polynomial equations.  相似文献   

15.
This randomised controlled trial investigated changes in eccentric hamstring strength, 10m sprint speed, and change-of-direction (COD) performance immediately post Nordic hamstring curl (NHC) intervention and following a 3-week detraining period.

Fourteen male team sports athletes were randomised to a do-as-usual control group (CG; n = 7) or to a NHC intervention group (NHC; n = 7). Isokinetic dynamometry at 180°/s evaluated eccentric hamstring strength immediately post-intervention as the primary outcome measure. Secondary outcomes included 10 m sprint time and COD. Each outcome was measured, pre, immediately post-intervention and following a 3-week detraining period.

Immediately post-intervention significant group differences were observed in the NHC group for eccentric hamstring strength (31.81 Nm?1 vs. 6.44 Nm?1, P = 0.001), COD (?0.12 s vs. 0.20 s; P = 0.003) and sprint (- 0.06 s vs. 0.05 s; P = 0.024) performance. Performance improvements were maintained following a detraining period for COD (?0.11 s vs. 0.20 s; P = 0.014) and sprint (?0.05 s vs. 0.03 s, P = 0.031) but not eccentric hamstring strength (15.67 Nm?1 vs. 6.44 Nm?1, P = 0.145) These findings have important implications for training programmes designed to reduce hamstring injury incidence, whilst enhancing physical qualities critical to sport.  相似文献   


16.
Abstract

The aim of this study was to determine potential relationships between anthropometric parameters and athletic performance with special consideration to repeated-sprint ability (RSA). Sixteen players of the senior male Qatar national soccer team performed a series of anthropometric and physical tests including countermovement jumps without (CMJ) and with free arms (CMJwA), straight-line 20 m sprint, RSA (6 × 35 m with 10 s recovery) and incremental field test. Significant (P < 0.05) relationships occurred between muscle-to-bone ratio and both CMJs height (r ranging from 0.56 to 0.69) as well as with all RSA-related variables (r < –0.53 for sprinting times and r = 0.54 for maximal sprinting speed) with the exception of the sprint decrement score (Sdec). The sum of six skinfolds and adipose mass index were largely correlated with Sdec (r = 0.68, P < 0.01 and r = 0.55, P < 0.05, respectively) but not with total time (TT, r = 0.44 and 0.33, P > 0.05, respectively) or any standard athletic tests. Multiple regression analyses indicated that muscular cross-sectional area for mid-thigh, adipose index, straight-line 20 m time, maximal sprinting speed and CMJwA are the strongest predictors of Sdec (r2 = 0.89) and TT (r2 = 0.95) during our RSA test. In the Qatar national soccer team, players’ power-related qualities and RSA are associated with a high muscular profile and a low adiposity. This supports the relevance of explosive power for the soccer players and the larger importance of neuromuscular qualities determining the RSA.  相似文献   

17.
Purpose: The aim of this study was to examine the effect of active versus passive recovery on 6 repeated Wingate tests (30-s all-out cycling sprints on a Velotron ergometer). Method: Fifteen healthy participants aged 29 (SD = 8) years old (body mass index = 23 [3] kg/m2) participated in 3 sprint interval training sessions separated by 3 to 7 days between each session during a period of 1 month. The 1st visit was familiarization to 6 cycling sprints; the 2nd and 3rd visits involved a warm-up followed by 6 30-s cycling sprints. Each sprint was followed by 4 min of passive (resting still on the ergometer) or active recovery (pedaling at 1.1 W/kg). The same recovery was used within each visit, and recovery type was randomized between visits. Results: Active recovery resulted in a 0.6 W/kg lower peak power output in the second sprint (95% confidence interval [CI] [ ? 0.2, ? 0.8 W/kg], effect size = 0.50, p < .01) and a 0.4 W/kg greater average power output in the 5th and 6th sprints (95% CI [+0.2,+0.6 W/kg], effect size = 0.50, p < .01) compared with passive recovery. There was little difference between fatigue index, total work, or accumulated work between the 2 recovery conditions. Conclusions: Passive recovery is beneficial when only 2 sprints are completed, whereas active recovery better maintains average power output compared with passive recovery when several sprints are performed sequentially (partial eta squared between conditions for multiple sprints = .38).  相似文献   

18.
Understanding the impact of friction in sled sprinting allows the quantification of kinetic outputs and the effective loading experienced by the athlete. This study assessed changes in the coefficient of friction (µk) of a sled sprint-training device with changing mass and speed to provide a means of quantifying effective loading for athletes. A common sled equipped with a load cell was towed across an athletics track using a motorised winch under variable sled mass (33.1–99.6 kg) with constant speeds (0.1 and 0.3 m · s?1), and with constant sled mass (55.6 kg) and varying speeds (0.1–6.0 m · s?1). Mean force data were analysed, with five trials performed for each condition to assess the reliability of measures. Variables were determined as reliable (ICC > 0.99, CV < 4.3%), with normal-force/friction-force and speed/coefficient of friction relationships well fitted with linear (R2 = 0.994–0.995) and quadratic regressions (R2 = 0.999), respectively (P < 0.001). The linearity of composite friction values determined at two speeds, and the range in values from the quadratic fit (µk = 0.35–0.47) suggested µk and effective loading were dependent on instantaneous speed on athletics track surfaces. This research provides a proof-of-concept for the assessment of friction characteristics during sled towing, with a practical example of its application in determining effective loading and sled-sprinting kinetics. The results clarify effects of friction during sled sprinting and improve the accuracy of loading applications in practice and transparency of reporting in research.  相似文献   

19.
ABSTRACT

This study aimed to investigate why futsal players decide to dribble. For this purpose, we analysed 396 trials comprising the dribbles (n = 132), passes (n = 131) or shots (n = 133), performed by 70 male futsal players. Passing and shooting angles, and interpersonal distance, including their rates of change (velocity and variability), were regarded as measures of interpersonal coordination tendency and a comparison was made among dribbling, passing and shooting situations. In addition, the variables identified as constraints on deciding to dribble were analysed in relation to age categories, dribbling outcomes and futsal court zone. Results revealed that passing and shooting angles, and interpersonal distance showed higher variability in dribbling than in passing and shooting situations. The findings allowed us to conclude that decision-making on dribbling was influenced by the variabilities of passing angles as well as shooting and interpersonal distance, and that success in dribbling was affected by the variability of interpersonal distance. Such variabilities were interpreted concerning their meaning of risk and/or uncertainty in the execution of motor skills.  相似文献   

20.
We determined if performance and mechanical running alterations during repeated treadmill sprinting differ between severely hot and hypoxic environments. Six male recreational sportsmen (team- and racket-sport background) performed five 5-s sprints with 25-s recovery on an instrumented treadmill, allowing the continuous (step-by-step) measurement of running kinetics/kinematics and spring-mass characteristics. These were randomly conducted in control (CON; 25°C/45% RH, inspired fraction of oxygen = 20.9%), hot (HOT; 38°C/21% RH, inspired fraction of oxygen = 20.9%; end-exercise core temperature: ~38.6°C) and normobaric hypoxic (HYP, 25°C/45% RH, inspired fraction of oxygen = 13.3%/simulated altitude of ~3600 m; end-exercise pulse oxygen saturation: ~84%) environments. Running distance was lower (P < 0.05) in HOT compared to CON and HYP for the first sprint but larger (P < 0.05) sprint decrement score occurred in HYP versus HOT and CON. Compared to CON, the cumulated distance covered over the five sprints was lower (P < 0.01) in HYP but not in HOT. Irrespective of the environmental condition, significant changes occurred from the first to the fifth sprint repetitions (all three conditions compounded) in selected running kinetics (mean horizontal forces, P < 0.01) or kinematics (contact and swing times, both P < 0.001; step frequency, P < 0.001) and spring-mass characteristics (vertical stiffness, P < 0.001; leg stiffness, P < 0.01). No significant interaction between sprint number and condition was found for any mechanical data. Preliminary evidence indicates that repeated-sprint ability is more impaired in hypoxia than in a hot environment, when compared to a control condition. However, as sprints are repeated, mechanical alterations appear not to be exacerbated in severe (heat, hypoxia) environmental conditions.  相似文献   

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