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Effect of Beta-Alanine Supplementation on Maximal Intensity Exercise in Trained Young Male Individuals: A Systematic Review and Meta-Analysis

George D. Georgiou, Kyriaki Antoniou, Stephanie Antoniou, Eleni Anna Michelekaki, Reza Zare, Ali Ali Redha, Konstantinos Prokopidis, Efstathios Christodoulides, and Tom Clifford

Beta-alanine is a nonessential amino acid that is commonly used to improve exercise performance. It could influence the buffering of hydrogen ions produced during intense exercise and delay fatigue, providing a substrate for increased synthesis of intramuscular carnosine. This systematic review evaluates the effects of beta-alanine supplementation on maximal intensity exercise in trained, young, male individuals. Six databases were searched on August 10, 2023, to identify randomized, double-blinded, placebo-controlled trials investigating the effect of chronic beta-alanine supplementation in trained male individuals with an age range of 18–40 years. Studies evaluating exercise performance through maximal or supramaximal intensity efforts falling within the 0.5–10 min duration were included. A total of 18 individual studies were analyzed, employing 18 exercise test protocols and 15 outcome measures in 331 participants. A significant (p = .01) result was observed with an overall effect size of 0.39 (95% confidence interval [CI] [0.09, 0.69]), in favor of beta-alanine supplementation versus placebo. Results indicate significant effects at 4 weeks of supplementation, effect size 0.34 (95% CI [0.02, 0.67], p = .04); 4–10 min of maximal effort, effect size 0.55 (95% CI [0.07, 1.04], p = .03); and a high beta-alanine dosage of 5.6–6.4 g per day, effect size 0.35 (95% CI [0.09, 0.62], p = .009). The results provide insights into which exercise modality will benefit the most, and which dosage protocols and durations stand to provide the greatest ergogenic effects. This may be used to inform further research, and professional or recreational training design, and optimization of supplementation strategies.

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How to Equalize High- and Low-Intensity Endurance Exercise Dose

Pekka Matomäki, Olli-Pekka Nuuttila, Olli J. Heinonen, Heikki Kyröläinen, and Ari Nummela

Purpose: Without appropriate standardization of exercise doses, comparing high- (HI) and low-intensity (LI) training outcomes might become a matter of speculation. In athletic preparation, proper quantification ensures an optimized stress-to-recovery ratio. This review aims to compare HI and LI doses by estimating theoretically the conversion ratio, 1:x, between HI and LI: How many minutes, x, of LI are equivalent to 1 minute of HI using various quantification methods? A scrutinized analysis on how the dose increases in relation to duration and intensity was also made. Analysis: An estimation was conducted across 4 categories encompassing 10 different approaches: (1) “arbitrary” methods, (2) physiological and perceptual measurements during exercise, (3) postexercise measurements, and comparison to (4a) acute and (4b) chronic intensity-related maximum dose. The first 2 categories provide the most conservative estimation for the HI:LI ratio (1:1.5–1:10), and the third, slightly higher (1:4–1:11). The category (4a) provides the highest estimation (1:52+) and (4b) suggests 1:10 to 1:20. The exercise dose in the majority of the approaches increase linearly in relation to duration and exponentially in relation to intensity. Conclusions: As dose estimations provide divergent evaluations of the HI:LI ratio, the choice of metric will have a large impact on the research designs, results, and interpretations. Therefore, researchers should familiarize themselves with the foundations and weaknesses of their metrics and justify their choice. Last, the linear relationship between duration and exercise dose is in many cases assumed rather than thoroughly tested, and its use should be subjected to closer scrutiny.

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Athletic Performance Decline Over the Life Span: Cross-Sectional and Longitudinal Analyses of Elite and Masters Track-and-Field Data

Brandon Pfeifer, W. Bradley Nelson, and Robert D. Hyldahl

Purpose : Loss of muscle power has a significant impact on mobility in geriatric populations, so this study sought to determine the extent and time course of performance decline in power-centric events throughout the life span via retrospective analyses of masters and elite track-and-field data. Methods : Four track-and-field events were selected based on maximal power output: the 100-m dash, long jump, high jump, and triple jump. Elite and masters athlete data were gathered from the World Masters Outdoor Championships and the International Amateur Athletic Federation World Athletics Championships (17,945 individual results). Data were analyzed by fitting individual and group results to quadratic and linear models. Results : Average age of peak performance in all events was 27.8 (0.8) years for men and 28.3 (0.8) years for women. Athlete performance decline best matched a linear model for the 5 years following peak performance (mean R 2  = .68 [.20]) and for ages 35–60, but best matched a quadratic model for ages 60–90 and 35–90 (mean R 2  = .75 [.12]). The average rate of decline for the masters data ages 35–60 ranged from 0.55% per year for men’s 100-m dash to 1.04% per year for women’s long jump. A significant age × sex interaction existed between men and women, with men declining faster throughout life in all events except the 100-m dash. Conclusions : Performance decline begins in the early 30s and is linear through middle age. This pattern of decline provides a basis for further research on power-decline pathophysiology and preventive measures starting in the 30s.

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A Change-Point Method to Detect Meaningful Change in Return-to-Sport Progression in Athletes

Kate K. Yung, Ben Teune, Clare L. Ardern, Fabio R. Serpiello, and Sam Robertson

Purpose: To explore how the change-point method can be used to analyze complex longitudinal data and detect when meaningful changes (change points) have occurred during rehabilitation. Method: This design is a prospective single-case observational study of a football player in a professional club who sustained an acute lower-limb muscle injury during high-speed running in training. The rehabilitation program was entirely completed in the football club under the supervision of the club’s medical team. Four wellness metrics and 5 running-performance metrics were collected before the injury and until the player returned to play. Results: Data were collected over 130 days. In the univariate analysis, the change points for stress, sleep, mood, and soreness were located on days 30, 47, 50, and 50, respectively. The change points for total distance, acceleration, maximum speed, deceleration, and high-speed running were located on days 32, 34, 37, 41, and 41, respectively. The multivariate analysis resulted in a single change point for the wellness metrics and running-performance metrics, on days 50 and 67, respectively. Conclusions: The univariate approach provided information regarding the sequence and time point of the change points. The multivariate approach provided a common change point for multiple metrics, information that would benefit clinicians to have a broad overview of the changes in the rehabilitation process. Clinicians may consider the change-point method to integrate and visualize data from multiple sources to evaluate athletes’ progression along the return-to-sport continuum.

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Predicting Future Athletic Performance in Young Female Road Cyclists Based on Aerobic Fitness and Hematological Variables

Dariusz Sitkowski, Jadwiga Malczewska-Lenczowska, Ryszard Zdanowicz, Michał Starczewski, Andrzej Pokrywka, Piotr Żmijewski, and Raphael Faiss

Purpose: This study aimed to determine whether the initial levels of aerobic fitness and hematological variables in young female road cyclists are related to their athletic performance development during their careers. Methods: Results of graded exercise tests on a cycle ergometer and total hemoglobin mass (tHb-mass) measurements were analyzed in 34 female road cyclists (age 18.6 [1.9] y). Among them, 2 groups were distinguished based on their competitive performance (Union Cycliste Internationale world ranking) over the following 8 years. Areas under the curve in receiver-operating-characteristic curves were calculated as indicators of elite-performance prediction. Results: Initial graded exercise test variables (peak power, peak oxygen uptake, and power at 4 mmol/L blood lactate) were not significantly different in elite (n = 13) versus nonelite (n = 21) riders. In contrast, elite riders had higher tHb-mass expressed either in absolute measures (664 [75] vs 596 [59] g, P = .006) or normalized to body mass (11.2 [0.8] vs 10.3 [0.7] g/kg, P = .001) and fat-free mass (14.4 [0.9] vs 13.1 [0.9] g/kg, P < .001). Absolute and relative erythrocyte volumes were significantly higher in elite subjects (P ranged from < .001 to .006). Of all the variables analyzed, the relative tHb-mass had the highest predictive ability to reach the elite level (area under the curve ranged from .82 to .85). Conclusion: Measurement of tHb-mass can be a helpful tool in talent detection to identify young female road cyclists with the potential to reach the elite level in the future.

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Retraction. Pharmacokinetic Profile of Caffeine and Its Two Main Metabolites in Dried Blood Spots After Five Different Oral Caffeine Administration Forms—A Randomized Crossover Study

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Test–Retest Reliability and Usefulness of a Foot–Ankle Rebound-Jump Test for Measuring Foot–Ankle Reactive Strength in Athletes

Romain Tourillon, François Fourchet, Pascal Edouard, and Jean-Benoît Morin

Purpose: This study investigated the test–retest reliability and usefulness of the foot–ankle rebound-jump test (FARJT) for measuring foot–ankle reactive strength metrics in athletes. Methods: Thirty-six highly trained, healthy athletes (5 female; 21.5 [3.9] y; 1.80 [0.10] m; 72.7 [10.4] kg) performed 8 repeated bilateral vertical foot–ankle rebound jumps on 2 testing days. Testing days were 1 week apart, and these sessions were preceded by a familiarization session. Reactive strength metrics were calculated by dividing jump height (in meters) by contact time (in seconds) for the reactive strength index (RSI) and flight time (in seconds) by contact time (in seconds) for the reactive strength ratio (RSR). The mean of 4 jumps (excluding the first and last 2 jumps) on each testing session were considered for RSI and RSR reliability and usefulness analysis. Results: We found a high reliability of the FARJT for RSI (intraclass correlation coefficient [ICC] > .90 and coefficient of variation [CV] = 12%) and RSR (ICC ≥ .90 and CV = 8%). Regarding their usefulness, both RSI and RSR were rated as “marginal” in detecting the smallest worthwhile change (typical error > smallest worthwhile change) and “good” in detecting a moderate change in performance. Conclusions: The results showed that a FARJT is a highly reliable test for measuring foot–ankle reactive strength in athletes and useful for quantifying changes, for example, following a training block. However, its usefulness as an accurate daily or weekly monitoring tool in practice is questionable.

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Can We Just Play? Internal Validity of Assessing Physiological State With a Semistandardized Kicking Drill in Professional Australian Football

Adriano Arguedas-Soley, Tzlil Shushan, Andrew Murphy, Nicholas Poulos, Ric Lovell, and Dean Norris

Purpose: To examine associations between exercise heart rate (HRex) during a continuous-fixed submaximal fitness test (CF-SMFT) and an intermittent-variable protocol (semistandardized kicking drill [SSD]) in Australian Football athletes, controlling for external intensities, within-session scheduling, and environmental conditions. Methods: Forty-four professional male Australian Football athletes (22.8 [8.0] y) were monitored over 10 sessions involving a 3-minute CF-SMFT (12 km·h−1) as the first activity and a SSD administered 35.7 (8.0) minutes after the CF-SMFT. Initial heart rate and HRex were collected, with external intensities measured as average velocity (in meters per minute) and average acceleration–deceleration (in meters per second squared). Environmental conditions were sampled. A penalized hierarchical linear mixed model was tuned for a Bayesian information criterion minima using a 10-fold cross-validation, with out-of-sample prediction accuracy assessed via root-mean-squared error. Results: SSD average acceleration–deceleration, initial heart rate, temperature, and ground hardness were significant moderators in the tuned model. When model covariates were held constant, a 1%-point change in SSD HRex associated with a 0.4%-point change in CF-SMFT HRex (95% CI, 0.3–0.5). The tuned model predicted CF-SMFT HRex with an average root-mean-squared error of 2.64 (0.57) over the 10-fold cross-validation, with 74% and 86% of out-of-sample predictions falling within 2.7%-points and 3.7%-points, respectively, from observed values, representing the lower and upper limits for detecting meaningful changes in HRex according to the documented typical error. Conclusions: Our findings support the use of an SSD to monitor physiological state in Australian Football athletes, despite varied scheduling within session. Model predictions of CF-SMFT HRex from SSD HRex closely aligned with observed values, considering measurement imprecision.

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The Anabolic Response to Protein Ingestion During Recovery From Exercise Has No Upper Limit in Magnitude and Duration In Vivo in Humans: A Commentary

Oliver C. Witard and Samuel Mettler

A comprehensive recent study by Trommelen et al. demonstrated that muscle tissue exhibits a greater capacity to incorporate exogenous exogenous protein-derived amino acids into bound muscle protein than was previously appreciated, at least when measured in “anabolically sensitive,” recreationally active (but not resistance-trained), young men following resistance exercise. Moreover, this study demonstrated that the duration of the postprandial period is modulated by the dose of ingested protein contained within a meal, that is, the postexercise muscle protein synthesis response to protein ingestion was more prolonged in 100PRO than 25PRO. Both observations represent important scientific advances in the field of protein metabolism. However, we respectfully caution that the practical implications of these findings may have been misinterpreted, at least in terms of dismissing the concept of protein meal distribution as an important factor in optimizing muscle tissue anabolism and/or metabolic health. Moreover, based on emerging evidence, this idea that the anabolic response to protein ingestion has no upper limit does not appear to translate to resistance-trained young women.

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Protein Intake Distribution: Beneficial, Detrimental, or Inconsequential for Muscle Anabolism? Response to Witard & Mettler

Jorn Trommelen, Andrew M. Holwerda, and Luc J.C. van Loon