Caffeine is a proven ergogenic aid that enhances exercise performance by delaying fatigue and increasing alertness. However, its limitations, including tolerance, adverse effects, and individual variability, have led to growing interest in non-stimulant pre-workout supplements. These alternatives aim to sustain energy and focus without the side effects of caffeine.
By Hugo Francisco de SouzaReviewed by Benedette Cuffari, M.Sc. Caffeine Use in Sports: Benefits, Tolerance, and Limitations Defining Non-Stimulant Pre-Workout Formulations Key Ingredients for Energy and Endurance Secondary Ingredients With Potential Performance Benefits Performance Gains vs. Real-World Variability Safety, Dosing, and Expectations Conclusions References Further Reading Caffeine is an established ergogenic aid that improves exercise performance by delaying fatigue and increasing alertness.
Despite its efficacy, limitations such as tolerance, adverse effects, and interindividual variability have driven growing interest in non-stimulant alternatives. Image Credit: Tatiana Kim / Shutterstock.com Caffeine Use in Sports: Benefits, Tolerance, and Limitations Researchers estimate that 70 % of young adults consume at least one nutritional supplement, with 30 % reporting regular use of pre-workout energy products.
Modern sports science defines pre-workout supplements as mixtures consumed before exercise to increase the availability of energy substrates, thereby creating physiological conditions that favor endurance and muscle mass gain.1,2 Caffeine is a methylxanthine adenosine receptor antagonist that delays the perception of fatigue and enhances fat oxidation. Chronic caffeine consumption reduces tolerance, subsequently necessitating higher doses to achieve the same ergogenic effect.
High caffeine intake increases the risk of common side effects such as jitters and insomnia, thus emphasizing the need for alternative ingredients that sustain energy and focus. The widespread prevalence of individuals with high caffeine sensitivity has similarly encouraged the exploration of non-caffeinated alternatives.1,3 Defining Non-Stimulant Pre-Workout Formulations Multi-ingredient pre-workout supplements incorporate a wide range of ingredients, such as amino acids, nitric oxide compounds to increase energy, and creatine to enhance athletic performance.3 Compared to stimulants like caffeine and nicotine, which target the areas of the brain that perceive work and fatigue, non-stimulant ingredients mediate biochemical pathways that maintain endurance and blood flow.
At the same time, they address fatigue through physiological mechanisms.3 Unfortunately, reviews highlight persistent challenges in defining the efficacy of these products due to proprietary blends that do not disclose specific dosages of individual active compounds.3 Key Ingredients for Energy and Endurance Beta-Alanine Beta-alanine is the rate-limiting precursor to carnosine or β-alanyl-L-histidine. Carnosine is a dipeptide that buffers hydrogen ions generated during high-intensity exercise, thereby delaying the onset of metabolic acidosis to support sustained muscular effort.4 Previous research has investigated the efficacy of acute single doses of beta-alanine before physical exercise; however, these formulations were largely ineffective.
Rather, the National Institutes of Health Office of Dietary Supplements recommends a minimum of two to four weeks of intake to saturate muscle carnosine reservoirs.5 One study suggests that fragmented dosing protocols of 4-6.4 g per day, with these doses divided into smaller servings throughout the day to minimize paresthesia, effectively enhance maximal strength and power-related outcomes for up to eight weeks.4 Beta Alanine Explained in 60 Seconds - Better Than Your Typical Supplement? Play Video credit: PictureFit / Shutterstock.com Creatine Creatine monohydrate is one of the most studied, safest, and effective supplements for increasing strength and energy supply during high-intensity activity.
Numerous studies confirm that creatine facilitates rapid rephosphorylation of adenosine diphosphate to adenosine triphosphate through the phosphocreatine system, significantly enhancing energy reserves.5 Even a short-term loading protocol of 0.3 g/kg for three consecutive days can significantly increase repetitions completed at 60-80 % 1-repetition maximum and reduce cardiovascular strain during exercise in resistance-trained athletes.6 Citrulline and NO Boosters L-citrulline and citrulline malate act as NO enhancers by improving vasodilation and muscle oxygenation during strenuous physical exercise and post-exercise recovery. Previously, CM supplementation has been reported to reduce muscle soreness by up to 41.8 % between 24 and 48 hours after exercising.7 Importantly, citrulline supplementation may not improve oxygen uptake kinetics.
One meta-analysis of aerobic performance showed no statistically significant difference between users and controls during low-intensity exercise. These findings suggest that the primary benefits of citrulline intake are more evident during anaerobic or high-intensity interval efforts.7 Secondary Ingredients With Potential Performance Benefits Taurine and L-tyrosine Taurine is an essential amino acid that regulates cellular hydration and calcium handling.
Acute doses of taurine have demonstrated a significant positive effect on endurance in hot environments, with studies revealing a Bayesian P-score ranking of 12.8 % for improving endurance capacity.8 L-tyrosine, a precursor to catecholamines such as adrenaline, noradrenaline, and dopamine, is associated with moderate-quality evidence suggesting it is generally ineffective for improving whole-body endurance performance. Consequently, L-tyrosine is only recommended to support cognitive function and focus when athletes experience significant mental fatigue or environmental stress, rather than as an endurance-enhancing supplement.9 Nitrates Research on inorganic nitrates, primarily derived from beetroot extracts, indicates that these compounds utilize a non-enzymatic pathway to increase NO bioavailability.
By reducing oxygen demand in skeletal muscles, NO supplementation mitigates exercise-induced acidic or hypoxic conditions. For example, chronic nitrate supplementation has been associated with statistically significant improvements in cyclists’ endurance time-trial performance.10 Image Credit: Snide12 / Shutterstock.com Performance Gains vs. Real-World Variability Acute MIPS ingestion can improve anaerobic power, the total volume of work completed in a resistance session, and improve anaerobic peak power output among athletes.
Nevertheless, these effects vary based on supplement combinations, dosages, ingestion timings, and athletes’ training status.1-3 Virability in formulation is highlighted as the most persistent current limitation in sports nutrition. Certain ingredients like creatine and beta-alanine require chronic loading to be effective, whereas nitrates and other compounds offer acute benefits, which further contribute to interindividual differences.3 Safety, Dosing, and Expectations Most non-stimulant pre-workout supplements are generally safe when consumed in recommended doses.
Although cardiovascular events like palpitations have been documented, these adverse effects are often restricted to individuals with preexisting health conditions or specific intolerances.2 The NIH Office of Dietary Supplements shows that the most commonly reported side effect in sports nutrition research is paresthesia following high doses; however, these events are temporary and considered physiologically harmless. In fact, emerging data suggest that certain components, such as taurine and citrulline, may confer cardioprotective benefits by improving consumers’ endothelial function and reducing homocysteine levels.2,5 Consumers are advised to select products based on ingredient transparency and align supplement use with their specific training goals.
Specifically, creatine and beta-alanine can be taken daily for chronic adaptations, whereas NO boosters between 60 and 120 minutes before exercise can provide hemodynamic support.3,5 Conclusions Non-caffeine supplements are widely used to enhance exercise capacity and cardiovascular resilience. A balanced approach that prioritizes high-quality, transparently labeled products, alongside proper diet and hydration, remains the most effective strategy for optimizing athletic performance. References Further Reading Further ReadingMore... Last Updated: May 1, 2026
Caffeine Sports Performance Pre-Workout Supplements Ergogenic Aids Non-Stimulant Alternatives
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