Serum Electrolyte Levels and Muscle Cramp Frequency in Long-Distance Runners During the Ibadan City Marathon, South West Nigeria

Background: Exercise-associated muscle cramps in endurance athletes have been attributed in part to electrolyte imbalances arising from sweat losses during prolonged physical exertion. Long-distance road races in tropical climates such as Ibadan, with high ambient temperature and humidity, present significant risk for electrolyte depletion. Characterising electrolyte dynamics in Nigerian recreational marathon runners addresses a notable knowledge gap. Objectives: This study aims to measure pre-race and immediate post-race serum sodium, potassium, chloride, and magnesium levels among participants in the Ibadan City Marathon and to examine the association between electrolyte changes and self-reported muscle cramp frequency during the race. Methods: Sixty consenting runners will provide venous blood samples before and within 15 minutes of completing the race. A brief structured questionnaire will document cramp occurrence, site, and severity. Paired t-tests will compare pre- and post-race electrolyte values. Chi-square analysis will examine the relationship between cramping and electrolyte depletion categories. Expected Outcomes: Post-race sodium and magnesium levels are anticipated to decline significantly, with hyponatraemia and hypomagnesaemia correlating with higher muscle cramp frequency. Conclusion: Outcomes will inform hydration and nutrition strategies for long-distance runners competing in tropical Nigerian conditions. Keywords: electrolytes, muscle cramps, marathon, endurance exercise, Ibadan.