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Creatine is the most studied ergogenic aid available. Daily supplementation raises muscle phosphocreatine stores by roughly 20–40%, which supports repeated high-intensity work and training adaptation. Newer meta-analyses suggest benefits for memory and processing, especially under stress or sleep deprivation.

• Kreider RB, et al. (2017). International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr.
• Avgerinos KI, et al. (2018). Effects of creatine supplementation on cognitive function of healthy individuals: a systematic review of randomized controlled trials. Exp Gerontol.
• Xu C, et al. (2024). Effects of creatine supplementation on cognitive function in adults: a systematic review and meta-analysis. Front Nutr.

For efforts beyond 2.5 hours, guidelines support up to 90 g of carbohydrate per hour from multiple transportable carbohydrates. Glucose-fructose blends raise exogenous oxidation rates and reduce gastrointestinal complaints versus single-source glucose.

• Jeukendrup A. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med.
• Thomas DT, Erdman KA, Burke LM. (2016). American College of Sports Medicine joint position statement: nutrition and athletic performance. Med Sci Sports Exerc.

Sweat sodium varies roughly 10-fold between athletes. For long or hot sessions, replacing sodium supports plasma volume and fluid retention. Guidance for exercise in heat recommends individualised sodium replacement for heavy and salty sweaters.

• McCubbin AJ, et al. (2020). Sports Dietitians Australia position statement: nutrition for exercise in hot environments. Int J Sport Nutr Exerc Metab.
• Thomas DT, Erdman KA, Burke LM. (2016). American College of Sports Medicine joint position statement: nutrition and athletic performance. Med Sci Sports Exerc.

Protein supplementation augments gains in muscle mass and strength with resistance training, with benefits plateauing around 1.6 g/kg/day. Whey is fast-digesting and leucine-rich, making it an efficient post-exercise protein.

• Jäger R, et al. (2017). International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr.
• Morton RW, et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med.

The heart and brain claims for EPA and DHA are among the best-established in nutrition. In athletes, omega-3 supplementation has been linked to reduced muscle soreness and better preservation of muscle during disuse, though performance effects are mixed.

• Philpott JD, Witard OC, Galloway SDR. (2019). Applications of omega-3 polyunsaturated fatty acid supplementation for sport performance. Res Sports Med.

Vitamin D insufficiency is widespread among athletes, especially in winter and among indoor-sport populations. Correcting deficiency supports musculoskeletal and immune health; supplementing beyond sufficiency hasn't been shown to boost performance.

• Owens DJ, Allison R, Close GL. (2018). Vitamin D and the athlete: current perspectives and new challenges. Sports Med.

Meta-analyses show that cooling before and during exercise improves performance in the heat, with mixed methods (vest plus ice slurry) among the most effective. Vests reduce skin temperature and perceived heat strain.

• Tyler CJ, Sunderland C, Cheung SS. (2015). The effect of cooling prior to and during exercise on exercise performance and capacity in the heat: a meta-analysis. Br J Sports Med.
• Bongers CCWG, Hopman MTE, Eijsvogels TMH. (2017). Cooling interventions for athletes: an overview of effectiveness, physiological mechanisms, and practical considerations. Temperature.

Low-load training with blood flow restriction produces muscle growth comparable to high-load training and meaningful strength gains. It's widely used in rehabilitation. Methodology and safety screening matter.

• Patterson SD, et al. (2019). Blood flow restriction exercise: considerations of methodology, application, and safety. Front Physiol.
• Lixandrão ME, et al. (2018). Magnitude of muscle strength and mass adaptations between high-load resistance training versus low-load resistance training associated with blood-flow restriction: a systematic review and meta-analysis. Sports Med.

Beta-alanine raises muscle carnosine and improves performance in 1–4 minute efforts. Dietary nitrate lowers the oxygen cost of exercise, with the clearest effects in recreational athletes. Caffeine is consistently ergogenic at 3–6 mg/kg; 150 mg sits at the low end to limit sleep disruption.

• Trexler ET, et al. (2015). International society of sports nutrition position stand: Beta-Alanine. J Int Soc Sports Nutr.
• Jones AM. (2014). Dietary nitrate supplementation and exercise performance. Sports Med.
• Guest NS, et al. (2021). International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr.
• Gonzalez AM, Trexler ET. (2020). Effects of citrulline supplementation on exercise performance in humans: a review of the current literature. J Strength Cond Res.

In a controlled trial, 15 g of vitamin C-enriched gelatin taken an hour before six minutes of rope-skipping doubled a blood marker of collagen synthesis. The evidence is promising but early, so we grade it B and keep the protocol specific.

• Shaw G, Lee-Barthel A, Ross ML, Wang B, Baar K. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. Am J Clin Nutr.

Several trials report faster recovery of strength and lower muscle soreness after marathon running and strenuous exercise with tart cherry. A meta-analysis also found small improvements in endurance performance. Effects are modest and vary between studies.

• Howatson G, et al. (2010). Influence of tart cherry juice on indices of recovery following marathon running. Scand J Med Sci Sports.
• Gao R, Chilibeck PD. (2020). Effect of tart cherry concentrate on endurance exercise performance: a meta-analysis. J Am Coll Nutr.

Glycine (3 g) before bed improved subjective sleep quality and next-day fatigue in small controlled studies. Magnesium supplementation has improved sleep measures in older adults with insomnia. Athletes with high sweat losses may run low on magnesium.

• Yamadera W, et al. (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep Biol Rhythms.
• Abbasi B, et al. (2012). The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial. J Res Med Sci.

Controlled trials show caffeine with L-theanine improves speed and accuracy on attention-switching tasks and reduces susceptibility to distraction versus placebo, with fewer reported jitters than caffeine alone.

• Owen GN, et al. (2008). The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci.

A meta-analysis found compression garments moderately improve recovery of strength and power and reduce soreness, with the largest effects 2–96 hours after exercise. Effects on running performance itself are small.

• Brown F, et al. (2017). Compression garments and recovery from exercise: a meta-analysis. Sports Med.
• Engel FA, et al. (2016). Is there evidence that runners can benefit from wearing compression clothing?. Sports Med.

Compression garments worn after exercise are associated with faster recovery of strength and reduced soreness. The strongest effects appear in the 24–96 hours after intense exercise.

• Brown F, et al. (2017). Compression garments and recovery from exercise: a meta-analysis. Sports Med.

Evening light suppresses melatonin, and short-wavelength (blue) light does so most strongly. Randomised trials of amber lenses in the evening report improvements in sleep quality, particularly in people with insomnia symptoms.

• Burkhart K, Phelps JR. (2009). Amber lenses to block blue light and improve sleep: a randomized trial. Chronobiol Int.
• Shechter A, et al. (2018). Blocking nocturnal blue light for insomnia: a randomized controlled trial. J Psychiatr Res.

Far-infrared-emitting fabrics have shown reduced soreness and improved perceived recovery in small randomised trials, including in elite footballers. Mechanisms are still being worked out and samples are small. That's why this is a C, and why we tell you so.

• Loturco I, et al. (2016). Effects of far infrared rays emitting clothing on recovery after an intense plyometric exercise bout applied to elite soccer players: a randomized double-blind placebo-controlled trial. Biol Sport.
• Vatansever F, Hamblin MR. (2012). Far infrared radiation (FIR): its biological effects and medical applications. Photonics Lasers Med.