RESUMEN
The present work is a trial to evaluate the effect of menstruation on electrolyte balance in response to muscular exercise. 30 volunteer girls from a faculty of physical education for girls participated in exercise program in form of running for 30 min. Pre and post exercise, blood samples were collected during menstruation and during the mid-menstrual cycle, and examined for their levels of sodium and potassium. Menstruation significantly decreased sodium level, both at rest and after muscular exercise [P < 0.05, P < 0.01 respectively]. Menstruation also significantly increased serum potassium level after muscular exercise [P < 0.001], than during the mid menstrual cycle. This work suggest that, the hyperkalemia and hyponatremia during menstruation may affect the female athletic performance and rendering them unfit for exercise during menstruation