Electrolytes and Summer Activity: Roles, Performance Impacts, and Replenishment Strategies

Brandon Hyatt, MS, CSCS

August 02, 2024 • 2 min read

Amid rising temperatures, the critical role of electrolytes in maintaining fluid balance, muscle function, and nerve signaling is often overlooked. While the importance of glucose for muscle fuel and protein/amino acids for repair is widely recognized, electrolytes—particularly sodium and potassium—are frequently neglected, even as they are lost through sweat.

Understanding how and when to replenish electrolytes is essential for thriving in heat. Whether you’re heading outdoors for cardio, traveling to a hiking destination, or planning summer recreation, electrolytes are non-negotiable. Below, we break down their physiological roles, performance implications, and optimal sources to help you maximize your summer plans.

Role in the Body

Electrolytes are minerals that dissolve in bodily fluids and carry a positive electrical charge (Lewis). Sodium—obtained through dietary intake—is excreted via sweat and urine, with renal function regulating its retention or elimination.

As the most abundant electrolyte in the body and diet, sodium is essential for survival. Its key functions include (Veniamakis):

• Regulation of blood pressure and volume

• Maintenance of organ perfusion

• Stimulation of muscle and nerve cells

• Balance of fluid and intravascular osmotic pressure

• Modulation of thirst and urine production

Other electrolytes play complementary roles in organ, nerve, and muscle function:

• Potassium

• Calcium

• Magnesium

• Chloride

• Bicarbonate

• Phosphorus

Impact on Performance

Given their centrality to human physiology, electrolytes are equally critical for athletic performance. Maintaining electrolyte balance during physical activity prevents adverse performance outcomes and reduces the risk of heat-related illnesses (Armstrong). Normal sodium levels also prevent hyponatremia (low serum sodium concentration).

Electrolyte balance is typically irrelevant for resistance training, as sessions are usually under two hours—often closer to one hour. Endurance activities, however, warrant careful attention to electrolyte status and replenishment.

In endurance events, minor performance declines occur with a 2–3% body weight loss from sweat; significant declines manifest at or above 4% loss (Armstrong).

Electrolyte Planning

All electrolytes can be adequately obtained through a balanced diet. Most individuals do not need to actively increase sodium or chloride intake, as these minerals are commonly added to foods (e.g., table salt) for flavor. High-electrolyte foods include:

• Potassium: Avocados, bananas, potatoes, spinach, legumes, squash

• Calcium: Dairy products, seeds, fish, lentils, leafy greens

• Magnesium: Nuts, seeds, legumes, grains, corn, dark chocolate, papaya

• Chloride: Table salt, processed meats/foods

• Phosphorus: Dairy, poultry, legumes, eggs, tofu

For workouts/activities lasting less than two hours (or one hour in hot, humid conditions), electrolytes can be restored through regular meals. For activities exceeding these durations, sodium replenishment is critical—it is the electrolyte most rapidly lost via sweat. Electrolyte supplements or beverages are the fastest, most efficient method, as they enable rapid absorption (unlike food, which requires digestion during exercise).

For activities over two hours, the recommended sodium intake is 300–600 mg/hour (Vitale). Conversely, post-exercise potassium replacement does not enhance rehydration (Vitale).

References

• Veniamakis E, Kaplanis G, Voulgaris P, Nikolaidis PT. Effects of Sodium Intake on Health and Performance in Endurance and Ultra-Endurance Sports. Int J Environ Res Public Health. 2022 Mar 19;19(6):3651. doi: 10.3390/ijerph19063651. PMID: 35329337; PMCID: PMC8955583.

• Vitale K, Getzin A. Nutrition and Supplement Update for the Endurance Athlete: Review and Recommendations. Nutrients. 2019 Jun 7;11(6):1289. doi: 10.3390/nu11061289. PMID: 31181616; PMCID: PMC6628334.

• Armstrong LE. Rehydration during Endurance Exercise: Challenges, Research, Options, Methods. Nutrients. 2021 Mar 9;13(3):887. doi: 10.3390/nu13030887. PMID: 33803421; PMCID: PMC8001428.