The role of electrolytes in endurance sports

The speed read: Electrolytes are critical for peak performance

Electrolytes regulate fluid balance, nerve and muscle function, and cardiovascular stability during endurance exercise. Tailoring sodium, potassium, and magnesium intake before, during, and after activity helps to prevent dehydration, cramps, and hyponatraemia. Recommended sodium intake ranges from approximately 200 mg per hour in cool conditions to 800-1,000 mg per hour in hot environments, reflecting individual sweat rates (Baker, 2017; Casa et al., 2000).

Electrolytes perform three essential tasks in your body

Fluid balance: Sodium and chloride maintain plasma volume and osmotic pressure, preventing both dehydration and over-hydration (Shirreffs & Sawka, 2011).

Muscle function: Sodium, potassium, calcium, and magnesium facilitate nerve impulses and excitation–contraction coupling in muscle fibres; imbalances increase cramp risk (Murray & Maughan, 2005).

Performance enhancement: Adequate electrolytes sustain plasma volume, support cardiovascular output, and delay fatigue and heat-related illness (Sawka & Montain, 2000).

Unmanaged electrolyte loss impairs performance and health

During prolonged exercise, athletes can lose 1-2 % of body mass in sweat per hour, containing 20–80 mmol/L sodium (460–1,840 mg), 3-6 mmol/L potassium, and smaller amounts of magnesium (Baker, 2017). Without replacement:

• Dehydration (>2 % body mass): diminishes endurance capacity and cognitive function. gssiweb.org
• Electrolyte imbalance: leads to muscle cramps, weakness, and potential arrhythmias. pmc.ncbi.nlm.nih.gov
• Exercise-associated hyponatraemia: excessive fluid intake without sodium lowers serum sodium, causing nausea, headache, and in severe cases seizures. pmc.ncbi.nlm.nih.gov
• Slowed recovery: inadequate post-exercise electrolyte restoration delays muscle repair and can impair immune function. pmc.ncbi.nlm.nih.gov
• Kidney stone risk: chronic underhydration and high urinary mineral concentration elevate stone formation risk in athletes. pubmed.ncbi.nlm.nih.gov

My approach to electrolyte intake

Before exercise: Consume about 500 mL of a carbohydrate-electrolyte solution roughly two hours before activity to achieve optimal hydration. pmc.ncbi.nlm.nih.gov

During exercise: For sessions longer than one hour, aim for 40-120 g carbohydrate per hour alongside approximately 250 mg sodium per hour in cool (<15 °C) and 800 mg per hour in warm (>22 °C) conditions, plus 20-50 mmol potassium and 2-5 mmol magnesium per hour. pmc.ncbi.nlm.nih.govgssiweb.org Use our personalised plan at https://truefuels.com/pages/fuel-guide to match intake to your sweat profile.

After exercise: Replace 100-150 % of fluid losses by drinking 1.2-1.5 L per kg body mass lost, with electrolyte concentrations of 20–50 mmol/L sodium to optimise rehydration.

References

[1] Baker, L. B. (2017). Sweating rate and sweat sodium concentration in athletes: A review of methodology and intra/interindividual variability. Sports Medicine, 47(Suppl 1), 111–128. https://doi.org/10.1007/s40279-017-0691-5

[2] Casa, D. J., Armstrong, L. E., Hillman, S. K., Montain, S. J., Reiff, R. V., Rich, B. S., Roberts, W. O., & Stone, J. A. (2000). National Athletic Trainers' Association position statement: fluid replacement for athletes. Journal of Athletic Training, 35(2), 212–224.

[3] Murray, R., & Maughan, R. J. (2005). Sports drink formulation. Sports Medicine, 35(10), 841–861. https://doi.org/10.2165/00007256-200535100-00002

[4] Prezioso, D., Strazzullo, P., Lotti, T., Bianchi, G., Borghi, L., Caione, P., Carini, M., Caudarella, R., Ferraro, M., Gambaro, G., Gelosa, M., Guttilla, A., Illiano, E., Martino, M., Meschi, T., Messa, P., Miano, R., Napodano, G., Nouvenne, A., Rendina, D., Rocco, F., Rosa, M., Sanseverino, R., Salerno, A., Spatafora, S., Tasca, A., Ticinesi, A., Travaglini, F., Trinchieri, A., Vespasiani, G., & Zattoni, F.; CLU Working Group. (2015). Dietary treatment of urinary risk factors for renal stone formation. Arch Ital Urol Androl, 87(2), 105–120. https://doi.org/10.4081/aiua.2015.2.105

[5] Sawka, M. N., & Montain, S. J. (2000). Fluid and electrolyte supplementation for exercise heat stress. American Journal of Clinical Nutrition, 72(2 Suppl), 564S–572S. https://doi.org/10.1093/ajcn/72.2.564S

[6] Shirreffs, S. M., & Sawka, M. N. (2011). Fluid and electrolyte needs for training, competition, and recovery. Journal of Sports Sciences, 29(Suppl 1), S39–S46. https://doi.org/10.1080/02640414.2011.582600