Profiling Professional Rugby Union Activity After Peak Match Periods.

The aim of this investigation was to quantify professional rugby union player activity profiles after the most intense (peak) passages of matches. Movement data were collected from 30 elite and 30 subelite professional rugby union athletes across respective competitive seasons. Accelerometer-derived PlayerLoad and global navigation satellite system-derived measures of mean speed and metabolic power were analyzed using a rolling-average method to identify the most intense 5- to 600-second passages (ie, worst-case scenarios) within matches. Player activity profiles immediately post their peak 5- to 600-second match intensity were identified using 5 epoch duration-matched intervals. Mean speed, metabolic power, and PlayerLoad declined sharply (∼29%-86%) after the most intense 5 to 600 seconds of matches. Following the most intense periods of rugby matches, exercise intensity declined below the average match-half intensity 81% of the time and seldom returned to or exceeded it, likely due to a host of individual physical and physiological characteristics, transient and/or accumulative fatigue, contextual factors, and pacing strategies. Typically, player exercise intensities after the most intense passages of matches were similar between match halves, positional groups, and levels of rugby competition. Accurate identification of the peak exercise intensities of matches and movement thereafter using novel methodologies has improved the limited understanding of professional rugby union player activity profiles following the worst-case scenarios of matches. Findings of the present study may inform match-representative training prescription, monitoring, and tactical match decisions (eg, substitutions and positional changes).

Modeling Professional Rugby Union Peak Intensity-Duration Relationships Using a Power Law.

PURPOSE: Can power law models accurately predict the peak intensities of rugby competition as a function of time? METHODS: Match movement data were collected from 30 elite and 30 subelite rugby union athletes across competitive seasons, using wearable Global Navigation Satellite Systems and accelerometers. Each athlete's peak rolling mean value of each measure (mean speed, metabolic power, and PlayerLoad™) for 8 durations between 5 seconds and 10 minutes was predicted by the duration with 4 power law (log-log) models, one for forwards and backs in each half of a typical match. RESULTS: The log of peak exercise intensity and exercise duration (5-600 s) displayed strong linear relationships (R2 = .967-.993) across all 3 measures. Rugby backs had greater predicted intensities for shorter durations than forwards, but their intensities declined at a steeper rate as duration increased. Random prediction errors for mean speed, metabolic power, and PlayerLoad were 5% to 6%, 7% to 9%, and 8% to 10% (moderate to large), respectively, for elite players. Systematic prediction errors across the range of durations were trivial to small for elite players, underestimating intensities for shorter (5-10 s) and longer (300-600 s) durations by 2% to 4% and overestimating 20- to 120-second intensities by 2% to 3%. Random and systematic errors were slightly greater for subelites compared to elites, with ranges of 4% to 12% and 2% to 5%, respectively. CONCLUSIONS: Peak intensities of professional rugby union matches can be predicted with adequate precision (trivial to small errors) for prescribing training drills of a given duration, irrespective of playing position, match half, level of competition, or measure of exercise intensity. However, practitioners should be aware of the substantial (moderate to large) prediction errors at the level of the individual player.

Sensitivity, reliability and construct validity of GPS and accelerometers for quantifying peak periods of rugby competition.

Training prescription and monitoring of team-sport athletes rely on accurate quantification of player movement. Our aim was to determine the sensitivity, reliability and construct validity of measures derived from a wearable device incorporating Global Positioning System (GPS) and accelerometer technology to quantify the peak periods of rugby competition. Match movement data were collected from 30 elite and 30 sub-elite rugby union players across respective competitive seasons. Accelerometer and GPS measures were analysed using a rolling average to identify peak movement for epochs ranging from 5 to 600 seconds. General linear mixed modelling was used to quantify the effects of playing position and match-half on the peak movement and variabilities within and between players represented reliability of each measure. Mean positional differences and match-half changes were assessed via standardisation and magnitude-based decisions. Sensitivity of measures was quantified via evaluation of ("signal") and typical error of measurement ("noise"). GPS and accelerometer measures had poor sensitivity for quantifying peak movement across all epochs and both levels of rugby union competition (noise 4× to 5× the signal). All measures displayed correspondingly low reliability across most epochs and both levels of competition (ICC<0.50). Construct validity was evident in mean differences between playing positions and match halves that were consistent with expected activity profiles in rugby union. However, it was clear from the pattern of differences across epoch durations and levels of competition that GPS and accelerometer measures provided different information about player movement. The poor sensitivity and low reliability of GPS and accelerometer measures of peak movement imply that rugby union players need to be monitored across many matches to obtain adequate precision for assessing individuals. Although all measures displayed construct validity, accelerometers provided meaningful information additional to that of GPS. We recommend using accelerometers alongside GPS to monitor and prescribe match respresentative training.

The effect of beta-alanine supplementation on isokinetic force and cycling performance in highly trained cyclists.

Beta-alanine may benefit short-duration, high-intensity exercise performance. The aim of this randomized double-blind placebo-controlled study was to examine the effects of beta-alanine supplementation on aspects of muscular performance in highly trained cyclists. Sixteen highly trained cyclists (mean ± SD; age = 24 ± 7 yr; mass = 70 ± 7 kg; VO2max = 67 ± 4 ml · kg(-1) · min(-1)) supplemented with either beta-alanine (n = 8, 65 mg · kg - 1BM) or a placebo (n = 8; dextrose monohydrate) over 4 weeks. Pre- and postsupplementation cyclists performed a 4-minute maximal cycling test to measure average power and 30 reciprocal maximal isokinetic knee contractions at a fixed angular velocity of 180° · sec(-1) to measure average power/repetition, total work done (TWD), and fatigue index (%). Blood pH, lactate (La-) and bicarbonate (HCO3-) concentrations were measured pre- and postisokinetic testing at baseline and following the supplementation period. Beta-alanine supplementation was 44% likely to increase average power output during the 4-minute cycling time trial when compared with the placebo, although this was not statistically significant (p = .25). Isokinetic average power/repetition was significantly increased post beta-alanine supplementation compared with placebo (beta-alanine: 6.8 ± 9.9 W, placebo: -4.3 ± 9.5 W, p = .04, 85% likely benefit), while fatigue index was significantly reduced (p = .03, 95% likely benefit). TWD was 89% likely to be improved following beta-alanine supplementation; however, this was not statistically significant (p = .09). There were no significant differences in blood pH, lactate, and HCO3- between groups (p > .05). Four weeks of beta-alanine supplementation resulted in worthwhile changes in time-trial performance and short-duration muscular force production in highly trained cyclists.

Effect of combined ß-alanine and sodium bicarbonate supplementation on cycling performance.

PURPOSE: The purpose of this study was to investigate the effects of 28 d of ß-alanine supplementation on 4-min cycling time trial performance and to determine whether there was an additive effect of combined ß-alanine and sodium bicarbonate (NaHCO3) supplementation on high-intensity cycling performance. METHODS: Fourteen highly trained cyclists (mean ± SD: age = 25.4 ± 7.2 yr, mass = 71.1 ± 7.1 kg, V˙O(2max) = 66.6 ± 5.7 mL·kg·min) supplemented for 28 d with ß-alanine (65 mg·kg body mass each day) or placebo. A maximal 4-min bout of cycling was performed before supplementation (baseline) and twice after supplementation: after ingestion of NaHCO3 (300 mg·kg body mass) and ingestion of a placebo using a randomized crossover design with 2 d between trials. Blood pH and HCO3 concentration were determined before loading (postsupplementation trials) and at pretest and posttest. RESULTS: In the acute NaHCO3 loading trials, blood pH and HCO3 were elevated from before loading to pretest, and the magnitude of the change in HCO3 from pretest to posttest was significantly greater compared with the acute placebo loading trial (P < 0.001). Average power output in the 4-min cycling performance trial was increased in placebo + NaHCO3 (+3.1% ± 1.8%) and ß-alanine + NaHCO3 (+3.3% ± 3.0%) compared with baseline (P < 0.05). ß-alanine + placebo did not significantly improve average power output compared with baseline (+1.6% ± 1.7%, P = 0.20); however, magnitude-based inferences demonstrated that ß-alanine + placebo was associated with a 37% likelihood of producing average power improvements. CONCLUSIONS: In trained cyclists, ß-alanine supplementation did not significantly improve 4-min cycling performance; however, there may be a small meaningful improvement in performance. Acute NaHCO3 supplementation significantly improved 4-min cycling performance. There seemed to be a minimal additive effect of combined ß-alanine and NaHCO3 supplementation.