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Keeron J. Stone and Jonathan L. Oliver

Purpose:

The aim of the study was to examine the effect of fatigue, developed during prolonged high-intensity intermittent exercise, on the performance of soccer shooting and dribbling skill.

Methods:

Nine semiprofessional soccer players with a mean age of 20.7 ± 1.4 years volunteered to participate in the study. Participants completed a slalom dribble test and the Loughborough Soccer Shooting Test (LSST), before and directly following the performance of three 15-min bouts of a modified version of the Loughborough Intermittent Shuttle Test (LIST).

Results:

Mean heart rates and mean 15-m sprint times remained unchanged across the three bouts of the LIST. Following the LIST slalom dribbling time increased significantly by 4.5 ± 4.0% (P = .009), while the mean total points scored during the LSST was significantly reduced by 7.6 ± 7.0 points (P = .012). When fatigued the frequency of shots in the LSST achieving the highest score of 5 points was reduced by 47% while the frequency of shots achieving the lowest 0 point score increased by 85%.

Conclusion:

Results show that while 45 min of exercise caused no decrements in sprint performance there were significant reductions in the ability to perform soccer-specific skills. Both the speed (dribbling time) and accuracy (shot performance) with which soccer-specific skills were executed was impaired following exercise replicating one-half of a soccer match.

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Cesar Marius Meylan, John Cronin, Will G. Hopkins and Jonathan Oliver

Adjustment for body mass and maturation of strength, power, and velocity measures of young athletes is important for talent development. Seventy-four youth male athletes performed a ballistic leg press test at five loads relative to body mass. The data were analyzed in maturity groups based on years from peak height velocity: −2.5 to −0.9 y (n = 29); −1.0 to 0.4 y (n = 28); and 0.5 to 2.0 y (n = 16). Allometric scaling factors representing percent difference in performance per percent difference in body mass were derived by linear regression of log-transformed variables, which also permitted adjustment of performance for body mass. Standardized differences between groups were assessed via magnitude-based inference. Strength and power measures showed a greater dependency on body mass than velocity-related variables (scaling factors of 0.56–0.85 vs. 0.42–0.14%/%), but even after adjustment for body mass most differences in strength and power were substantial (7–44%). In conclusion, increases in strength and power with maturation are due only partly to increases in body mass. Such increases, along with appropriate adjustment for body mass, need to be taken into account when comparing performance of maturing athletes.

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Jonathan L. Oliver, Craig A. Williams and Neil Armstrong

The purpose of this study was to assess the reliability of a field and a laboratory test of repeated sprint ability (RSA). Twelve adolescent boys (15.3 ± 0.3 years) completed five trials of both a field RSA test (7 × 30 m sprints) and a laboratory RSA test (7 × 5 s sprints) performed on a nonmotorized treadmill. Mean coefficients of variation (CV) calculated across all trials were < 2.7% for field sprint times, and, in the laboratory, < 2.9% for velocity and < 8.4% for power output. Fatigue indices (FI) calculated from data in both environments exhibited mean CVs > 23%. The inconsistency in the FIs resulted from the mathematical procedures used in the FI calculation methods. Based on the reliability scores, it was concluded that results obtained from measured performance variables in the field and laboratory, and not calculated FIs, should be used to report RSA.

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Michael C. Rumpf, John B. Cronin, Jonathan Oliver and Michael Hughes

Sprinting is an important physical capacity and the development of sprint ability can take place throughout the athlete’s growth. The purpose of this study therefore was to determine if the kinematics and kinetics associated with maximum sprint velocity differs in male youth participants of different maturity status (pre, mid- and postpeak height velocity (PHV)) and if maximum sprint velocity is determined by age, maturity or individual body size measurement. Participants (n = 74) sprinted over 30 meters on a nonmotorized treadmill and the fastest four consecutive steps were analyzed. Pre-PHV participants were found to differ significantly (p < .05) to mid- and post-PHV participants in speed, step length, step frequency, vertical and horizontal force, and horizontal power (~8-78%). However, only relative vertical force and speed differed significantly between mid and post-PHV groups. The greatest average percent change in kinetics and kinematics was observed from pre- to mid-PHV (37.8%) compared with mid- to post- PHV groups (11.6%). When maturity offset was entered as a covariate, there was no significant difference in velocity between the three groups. However, all groups were significantly different from each other when age was chosen as the covariate. The two best predictors of maximal velocity within each maturity group were power and horizontal force (R 2 = 97−99%) indicating the importance of horizontal force application while sprinting. Finally, maturity explained 83% of maximal velocity across all groups.

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Jonathan M. Oliver, Dustin P. Joubert, Steven E. Martin and Stephen F. Crouse

Purpose:

To determine the effects of creatine supplementation on blood lactate during incremental cycling exercise.

Methods:

Thirteen male subjects (M ± SD 23 ± 2 yr, 178.0 ± 8.1 cm, 86.3 ± 16.0 kg, 24% ± 9% body fat) performed a maximal, incremental cycling test to exhaustion before (Pre) and after (Post) 6 d of creatine supplementation (4 doses/d of 5 g creatine + 15 g glucose). Blood lactate was measured at the end of each exercise stage during the protocol, and the lactate threshold was determined as the stage before achieving 4 mmol/L. Lactate concentrations during the incremental test were analyzed using a 2 (condition) × 6 (exercise stage) repeated-measures ANOVA. Differences in power at lactate threshold, power at exhaustion, and total exercise time were determined by paired t tests and are presented as M ± SD.

Results:

Lactate concentrations were reduced during exercise after supplementation, demonstrating a significant condition effect (p = .041). There was a tendency for increased power at the lactate threshold (Pre 128 ± 45 W, Post 143 ± 26 W; p = .11). Total time to fatigue approached significant increases (Pre 22.6 ± 3.2 min, Post 23.3 ± 3.3 min; p = .056), as did maximal power output (Pre 212.5 ± 32.5 W, Post 220 ± 34.6 W; p = .082).

Conclusions:

Our findings demonstrate that creatine supplementation decreases lactate during incremental cycling exercise and tends to raise lactate threshold. Therefore, creatine supplementation could potentially benefit endurance athletes.

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Michael Clemens Rumpf, John Barry Cronin, Ikhwan Nur Mohamad, Sharil Mohamad, Jonathan Oliver and Michael Hughes

The purpose of this study was to investigate the effect of 2.5, 5, 7.5, and 10% body mass load on resisted sled towing 30 meter sprint times in male youth athletes of different maturity status. A total of 35 athletes (19 prepeak-height-velocity (PHV) and 16 mid/post-PHV) sprinted three times in an unloaded and each of the loaded conditions. The pre-PHV athletes were significantly slower (~33%; p < .05) than the more mature athletes across all loads (unloaded, 2.5, 5, 7.5, 10% body mass). Each incremental load (i.e., 2.5% body mass) was found to reduce 30 m sprint times by 3.70% (± 2.59) and 2.45% (± 1.48) for the pre- and mid/post-PHV respectively. The slopes of the pre- (y = 0.09 x + 5.71) and mid/post (y = 0.04 x + 4.38) regression equations were compared and found to be statistically different (p = .004) suggesting that athletes of different maturity status responded differentially to the same relative resisted sprint load. Ten percent body mass load resulted in a reduced sprint time of ~15.8 and ~9.8% for the pre- and mid/post-PHV group, respectively. These results enable predictive equations to be formulated and appropriate resisted sprint loading, based on the intended focus of a session.

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Robert W. Meyers, Jonathan L. Oliver, Michael G. Hughes, John B. Cronin and Rhodri S. Lloyd

The purpose of this study was to examine the natural development of the mechanical features of sprint performance in relation to maturation within a large cohort of boys. Three hundred and thirty-six boys (11-15 years) were analyzed for sprint performance and maturation. Maximal speed, stride length (SL), stride frequency (SF), flight time (FT) and contact time (CT) were assessed during a 30m sprint. Five maturation groups (G1-5) were established based on age from peak height velocity (PHV) where G1=>2.5years pre-PHV, G2 = 2.49-1.5years pre-PHV, G3 = 1.49-0.5years pre-PHV, G4 = 0.49years pre- to 0.5years post-PHV and G5 = 0.51-1.5years post-PHV. There was no difference in maximal speed between G1, G2 and G3 but those in G4 and G5 were significantly faster (p < .05) than G1-3. Significant increases (p < .05) in SL were observed between groups with advancing maturation, except G4 and G5 (p > .05). SF decreased while CT increased (both p < .05) between G1, G2 and G3, but no further significant changes (p > .05) were observed for either variable between G3, G4 and G5. While G1-3 increased their SL, concomitant decreases in SF and increases in CT prevented them from improving maximal speed. Maximal sprint speed appears to develop around and post-PHV as SF and CT begin to stabilize, with increases in maximal sprint speed in maturing boys being underpinned by increasing SL.

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Keeron J. Stone, Jonathan L. Oliver, Michael G. Hughes, Michael R. Stembridge, Daniel J. Newcombe and Robert W. Meyers

Existing procedures for the simulation of soccer match play fail to incorporate multidirectional and repeated-sprint activities, even though these movements are considered fundamental to match play. In the current study, selected physiological and performance responses were assessed during an adapted version of an existing soccer simulation protocol. Mean heart rates of 163 ± 14 beats·min–1, mean blood lactates of 4.9 ± 2.3 mmol·L-1 and decrements in single-sprint and repeated-sprint performances were observed. The presented adaptations to an existing soccer simulation protocol better reflect the movement characteristics as well as the physiological and performance responses of soccer match play.

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Justin J. Merrigan, James J. Tufano, Jonathan M. Oliver, Jason B. White, Jennifer B. Fields and Margaret T. Jones

Purpose: To examine rest redistribution (RR) effects on back squat kinetics and kinematics in resistance-trained women. Methods: Twelve women from strength and college sports (5.0 [2.2] y training history) participated in the randomized crossover design study with 72 hours between sessions (3 total). Participants completed 4 sets of 10 repetitions using traditional sets (120-s interset rest) and RR (30-s intraset rest in the middle of each set; 90-s interset rest) with 70% of their 1-repetition maximum. Kinetics and kinematics were sampled via force plate and 4 linear position transducers. The greatest value of repetitions 1 to 3 (peak repetition) was used to calculate percentage loss, [(repetition 10–peak repetition)/(peak repetition) × 100], and maintenance, {100–[(set mean–peak repetition)/(peak repetition)] × 100}, of velocity and power for each set. Repeated-measures analysis of variance was used for analyses (P < .05). Results: Mean and peak force did not differ between conditions. A condition × repetition interaction existed for peak power (P = .049) but not for peak velocity (P = .110). Peak power was greater in repetitions 7 to 9 (P < .05; d = 1.12–1.27) during RR. The percentage loss of velocity (95% confidence interval, –0.22% to –7.22%; P = .039) and power (95% confidence interval, –1.53% to –7.87%; P = .008) were reduced in RR. Mean velocity maintenance of sets 3 (P = .036; d = 1.90) and 4 (P = .015; d = 2.30) and mean power maintenance of set 4 (P = .006; d = 2.65) were greater in RR. Conclusion: By redistributing a portion of long interset rest into the middle of a set, velocity and power were better maintained. Therefore, redistributing rest may be beneficial for reducing fatigue in resistance-trained women.

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Jason D. Stone, Adam C. King, Shiho Goto, John D. Mata, Joseph Hannon, James C. Garrison, James Bothwell, Andrew R. Jagim, Margaret T. Jones and Jonathan M. Oliver

Purpose: To provide a joint-level analysis of traditional (TS) and cluster (CS) set structure during the back-squat exercise. Methods: Eight men (24 [3] y, 177.3 [7.9] cm, 82.7 [11.0] kg, 11.9 [3.5] % body fat, and 150.3 [23.0] kg 1-repetition maximum [1RM]) performed the back-squat exercise (80%1RM) using TS (4 × 6, 2-min interset rest) and CS (4 × [2 × 3], 30-s intraset rest, 90-s interset rest), randomly. Lower-limb kinematics were collected by motion capture, as well as kinetic data by bilateral force platforms. Results: CS attenuated the loss in mean power (TS −21.6% [3.9%]; CS −12.4% [7.5%]; P = .042), although no differences in gross movement pattern (sagittal-plane joint angles) within and between conditions were observed (P ≥ .05). However, joint power produced at the hip increased from repetition (REP) 1 through REP 6 during TS, while a decrease was noted at the knee. A similar pattern was observed in the CS condition but was limited to the hip. Joint power produced at the hip increased from REP 1 through REP 3 but returned to REP 1 values before a similar increase through REP 6, resulting in differences between conditions (REP 4, P = .018; REP 5, P = .022). Conclusions: Sagittal-plane joint angles did not change in either condition, although CS elicited greater power. Differing joint power contributions (hip and knee) suggest potential central mechanism that may contribute to enhanced power output during CS and warrant further study. Practitioners should consider incorporating CS into training to promote greater power adaptations and to mitigate fatigue.