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Summary

This journal article, published in the Journal of the International Society of Sports Nutrition, presents a research study investigating the effects of beta-alanine supplementation on competitive middle- and long-distance runners aged 15-19. The authors conducted a double-blind, placebo-controlled trial over four weeks to assess changes in aerobic performance, specifically focusing on time to exhaustion (TTE) and aerobic capacity (VO2peak). Their findings suggest that while beta-alanine did improve TTE, it had no significant impact on VO2peak in this adolescent athlete population. The article also discusses the physiological mechanisms behind these observed effects and offers practical applications for coaches and athletes.

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​Beta-alanine supplementation improves time to exhaustion, but not aerobic capacity, in competitive middle- and long-distance runners​
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Executive Summary

A study published in the Journal of the International Society of Sports Nutrition in 2025 investigated the effects of 4 weeks of beta-alanine (βA) supplementation on aerobic performance in competitive adolescent middle- and long-distance runners. The research aimed to fill a gap in existing literature, which primarily focuses on adult athletes. The key findings indicate that βA supplementation significantly improved time to exhaustion (TTE) in these adolescent runners, along with positive changes in ventilatory thresholds and certain submaximal performance variables (heart rate, respiratory exchange ratio). However, there was no significant increase in maximal aerobic capacity (VO2peak). This suggests that βA can be a beneficial ergogenic aid for adolescent endurance athletes, primarily by enhancing their ability to sustain high-intensity efforts and delay fatigue, rather than by directly increasing their VO2peak.

Main Themes and Important Findings

1. Beta-Alanine Enhances Time to Exhaustion (TTE)

• Key Finding: βA supplementation led to a notable increase in TTE during maximal-intensity exercise.
• Quantitative Data: The βA group increased TTE by 6.5% (23.6 ± 21.4 seconds) after 4 weeks, compared to a trivial 1.4% increase (approximately 5 seconds) in the placebo (PL) group. This represents a "large practical effect" (d = 1.05) within the βA group.
• Mechanism (Proposed): The study attributes this improvement to βA's role in increasing the synthesis of carnosine, a dipeptide that buffers hydrogen ions (H+) in skeletal muscle and the bloodstream. Accumulation of H+ contributes significantly to exercise-induced fatigue by disrupting phosphocreatine resynthesis, inhibiting glycolysis, and impairing ion transfer across cell membranes. By buffering H+, carnosine helps "attenuate reductions in pH, stave off fatigue, and ultimately improve performance."
• Quote: "While increasing the buffering capacity for H+ ions would not solely alleviate fatigue during exercise performance, multiple studies have demonstrated beneficial effects when consuming βA including delayed onset of neuromuscular fatigue, improved time to exhaustion (TTE), and increased total work completed."

2. No Significant Impact on Maximal Aerobic Capacity (VO2peak)

• Key Finding: Despite improvements in TTE, βA supplementation did not lead to a statistically significant increase in VO2peak (maximal oxygen uptake) in adolescent runners.
• Quantitative Data: The βA group showed a trivial average increase in VO2peak of 0.7 ± 3.6 ml·kg⁻¹·min⁻¹ (d = 0.18). The placebo group, surprisingly, demonstrated a moderate decrement in VO2peak of 3.6 ± 4.7 ml·kg⁻¹·min⁻¹ (d = 0.75).
• Context: The authors note that the observed increase in the βA group (1.6%) falls within the typical day-to-day variation of VO2peak testing (~2.6%), meaning it "cannot be stated that 4 weeks of βA supplementation had an effect on aerobic capacity."
• Consistency with Previous Research: This finding aligns with prior studies in adults that also reported trivial-to-no effect of βA on VO2peak.

3. Improvements in Ventilatory Thresholds (VT1 & VT2)

• Key Finding: βA supplementation significantly impacted the second ventilatory threshold (VT2), indicating improved tolerance to higher-intensity exercise.
• VT2 Changes: The βA group experienced a "delayed onset of VT2" as evidenced by increases in VO2 at VT2 (4.8% increase, d = 0.50) and velocity at VT2 (4.54% increase, d = 0.64). In contrast, the PL group experienced decreases in both VO2 at VT2 (6.6% decrease, d = 0.92) and velocity at VT2 (1.5% decrease, d = 0.21). The difference between groups for VO2 at VT2 was described as a "large practical change" (d = 1.34).
• VT1 Changes: For the first ventilatory threshold (VT1), within-subject changes in the βA group were small for VO2 (+5%) and velocity (+5.3%), and moderate for minute ventilation (VE) (+12.1%).
• Implication: These changes suggest that βA helps athletes sustain higher intensities for longer before reaching significant fatigue.

4. Positive Effects on Submaximal Running Performance

• Key Finding: During submaximal 1500-m treadmill runs, the βA group showed reduced average heart rate (HR) and respiratory exchange ratio (RER), indicating increased efficiency at submaximal intensities.
• HR and RER: The βA group decreased average HR by 4% (d = 0.48) and average RER by 0.04 (d = 0.69), while the PL group showed no change. These were considered "moderate practical differences" between groups.
• VO2 during SMT: While the βA group experienced a trivial 1.94% increase in average VO2 during the SMT, the PL group saw a 6.45% decrease.
• Practical Significance: These findings suggest βA may improve metabolic efficiency and cardiovascular response during sustained submaximal efforts, contributing to delayed fatigue in endurance events that include intermittent higher-intensity bouts.

5. Role of Hydrogen Ion Buffering and Carnosine Synthesis

• Core Mechanism: βA's primary function during exercise is to increase the synthesis of carnosine, a dipeptide crucial for buffering H+ ions.
• Impact of H+ Accumulation: The accumulation of H+ reduces pH, disrupting phosphocreatine resynthesis, inhibiting glycolysis, and impairing ion transfer, all of which contribute to early fatigue.
• Carnosine Levels: Consistent βA consumption (typically 3.2 to 6.4 g·day⁻¹ for 4 weeks or longer) has been shown to elevate carnosine levels by approximately 20-80% and improve H+ buffering capacity by 6-7%.
• Lactate Relationship: The study clarifies that lactate production consumes H+ ions, rather than releasing them. Therefore, trivial effects of βA on blood lactate concentrations post-exercise were expected and observed.

Important Details and Facts

• Study Population: 27 competitive adolescent middle- and long-distance runners (aged 17.36 ± 2.17 years; 13 males, 14 females), specifically training for 800m, 1500m, and 3000m events. 23 completed the study.
• Study Design: Double-blind, placebo-controlled pre-posttest design over 4 weeks.
• Supplementation Protocol:βA group: 6.4 g·d⁻¹ for males, 4.8 g·d⁻¹ for females (approximately 90 mg·kg⁻¹), taken three times per day with meals.
• Placebo group: Maltodextrin at the same dosages.
• Testing Procedures:Maximal Graded Exercise Tests (GXT): Performed at baseline, week 2, and week 4, measuring HRmax, VO2peak, TTE, ventilatory thresholds (VT1, VT2), and lactate (La).
• Submaximal Trials (SMT): 1500-m treadmill run at 80% of individual VO2peak, measuring average HR, VO2, RER, and post-exercise [La].
• Adverse Effects: Eight of eleven βA subjects experienced mild paresthesia (a common side effect) within 2 weeks; no other adverse effects were reported.
• Limitations:Duration: Only 4 weeks of supplementation, which is the minimum threshold for beneficial adaptations. Longer periods (e.g., ≥8 weeks) might yield further improvements.
• Carnosine Measurement: Skeletal muscle carnosine levels were not directly measured. The proposed mechanism of increased H+ buffering via carnosine is inferred from existing literature.
• Body Weight Fluctuations: Changes in individual body weight during the study had a negative relationship with VO2peak changes in the βA group, suggesting that VO2peak changes might not be solely attributable to supplementation.

Practical Applications

• For Coaches and Practitioners: The findings suggest that βA supplementation "may be a useful ergogenic strategy for endurance coaches working with adolescent athletes."
• Performance Benefits: While βA may not increase maximal aerobic capacity (VO2peak), it appears to "enhance performance by prolonging TTE and improving tolerance to higher-intensity segments during competition."
• Targeted Events: Beta-alanine's benefits are likely more pronounced in events or segments of events that produce higher levels of hydrogen ions (e.g., high-intensity bursts, surges, uphill sections, final sprints).
• Considerations for Adolescents: This study provides novel evidence in an adolescent population, addressing a gap where most previous research focused on adults. However, future research should investigate direct effects on carnosine accumulation and longer supplementation durations in adolescents, accounting for maturation and training status.

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Quiz

Instructions: Answer the following questions in 2-3 sentences each, based on the provided source material.

1. What was the primary purpose of this study regarding beta-alanine (βA) supplementation?
2. Which demographic group was the focus of this research, and why was this particular group chosen?
3. What is the main physiological role of beta-alanine during exercise, and what dipeptide does it help synthesize?
4. What specific performance variable showed significant improvement with βA supplementation in this study's adolescent runners?
5. Did βA supplementation lead to an increase in aerobic capacity (VO2peak) in the adolescent runners, according to the study's findings?
6. How did βA supplementation affect ventilatory thresholds, specifically VT2, in the experimental group compared to the placebo?
7. What were some of the key variables measured during the Submaximal Trials (SMT) in this study?
8. Describe the dosage protocol for βA and placebo administered to the male and female participants.
9. What is the proposed mechanism by which βA supplementation improves time to exhaustion?
10. What limitations did the authors identify in their study, and what future research did they suggest?

II. Quiz Answer Key

• The primary purpose of this study was to determine the effects of four weeks of beta-alanine supplementation on submaximal and maximal endurance performance in elite adolescent runners. Previous research had primarily focused on adults, leaving a knowledge gap for this younger athletic population.
• The study focused on adolescent middle- and long-distance runners aged 15–19 years. This group was chosen because, to the authors' knowledge, there was a lack of research addressing βA use in this specific competitive adolescent population, despite an abundance of evidence in adult athletes.
• The primary physiological role of beta-alanine during exercise is to increase the synthesis of carnosine. Carnosine is a dipeptide responsible for buffering hydrogen ions (H+), which accumulate during high-intensity exercise and contribute to fatigue.
• The specific performance variable that showed significant improvement with βA supplementation was Time to Exhaustion (TTE). The βA group increased TTE by 6.5%, whereas the placebo group only saw a 1.4% increase.
• No, βA supplementation did not lead to a statistically significant increase in aerobic capacity (VO2peak) in the adolescent runners. While the βA group showed a trivial increase, this change was within the observed day-to-day variation of VO2peak testing, indicating no true effect.
• βA supplementation led to a delayed onset of VT2, indicated by increases in VO2 and velocity at VT2 for the βA group, compared to decreases in the placebo group. This suggests an enhanced tolerance for higher-intensity exercise segments.
• During the Submaximal Trials (SMT), key variables collected included average and final heart rate (HR), average and final oxygen uptake (VO2), post-exercise blood lactate concentration ([La]), respiratory exchange ratio (RER), and rate of perceived exertion (RPE).
• Males in the supplement group received 6.4 g·d–1 of βA, while females received 4.8 g·d–1. The placebo group received corresponding dosages of maltodextrin (6.4 g·d–1 for males, 4.8 g·d–1 for females), all in pill form, consumed three times per day with meals.
• The proposed mechanism for βA supplementation improving time to exhaustion is likely an increase in intracellular hydrogen ion (H+) buffering. This buffering capacity is enhanced via a rise in muscle carnosine levels, which helps attenuate reductions in pH during high-intensity activities, thereby delaying fatigue.
• The limitations identified include the relatively short supplementation period of 4 weeks, and the fact that skeletal muscle carnosine levels were not directly measured. The authors suggested future research should examine longer durations of use (e.g., ≥8 weeks) and directly measure carnosine accumulation in adolescents, considering their maturation and training status.
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Glossary of Key Terms

• Aerobic Capacity (VO2peak/VO2max): The maximum rate of oxygen consumption measured during incremental exercise, reflecting the maximum capacity of an individual's body to transport and use oxygen during exercise.
• Beta-alanine (βA): A non-essential amino acid that serves as a precursor to carnosine synthesis; it is commonly used as a dietary supplement to enhance exercise performance.
• Carnosine: A dipeptide (composed of beta-alanine and L-histidine) found in high concentrations in skeletal muscle, primarily responsible for buffering hydrogen ions (H+) and reactive oxygen species during exercise.
• Double-blind, Placebo-controlled Design: A research design where neither the participants nor the researchers know who is receiving the experimental treatment (e.g., βA) and who is receiving the inactive substance (placebo), minimising bias.
• Effect Size (Cohen's d): A standardised measure of the magnitude of an observed effect, used to quantify the difference between two groups or conditions, independent of sample size.
• Graded Exercise Test (GXT): A maximal exercise test where exercise intensity is progressively increased until the participant reaches volitional exhaustion, used to determine maximal performance variables like VO2peak and TTE.
• Hydrogen Ions (H+): Ions that accumulate in skeletal muscle and bloodstream during intense exercise, leading to a reduction in pH (acidosis) and contributing to fatigue by disrupting metabolic processes.
• Maltodextrin: A polysaccharide commonly used as a food additive, often serving as a placebo in supplement studies due to its similar appearance and taste to some supplements.
• Minute Ventilation (VE): The total volume of air exhaled or inhaled per minute, an indicator of respiratory effort during exercise.
• Placebo (PL): An inactive substance or treatment given to a control group in a study to compare its effects with those of an active drug or treatment.
• Rate of Perceived Exertion (RPE): A subjective measure of exercise intensity, typically assessed using a scale (e.g., Borg RPE scale 6–20), indicating how hard a person feels they are working.
• Repeated Measures Mixed Model Analysis of Variance: A statistical test used to analyse data where the same subjects are measured multiple times under different conditions, allowing for the assessment of both within-group and between-group differences.
• Respiratory Exchange Ratio (RER): The ratio of carbon dioxide produced to oxygen consumed (VCO2/VO2), used to estimate the relative contribution of carbohydrate and fat to energy metabolism during exercise.
• Smallest Worthwhile Change (SWC): A quantitative measure used to determine if an observed change in a variable is clinically or practically meaningful, often calculated based on typical day-to-day variability.
• Submaximal Trial (SMT): An exercise test performed at an intensity below the maximum, designed to assess physiological responses and performance during sustained, moderate-intensity effort.
• Time to Exhaustion (TTE): The total duration an individual can sustain an exercise task at a given intensity until they can no longer continue, a measure of endurance performance.
• Ventilatory Threshold 1 (VT1): The first ventilatory threshold, representing the point during exercise where ventilation begins to increase disproportionately to oxygen consumption, often associated with the aerobic threshold.
• Ventilatory Threshold 2 (VT2): The second ventilatory threshold, indicating a further disproportionate increase in ventilation, typically associated with the anaerobic threshold or respiratory compensation point, reflecting the point where lactate accumulation significantly increases.

NotebookLM can be inaccurate; please double-check its responses.