PT  - JOURNAL ARTICLE
AU  - D N Prashad
AU  - P A Fletcher
AU  - M Cooper
TI  - Exercise-induced changes in urinary water and mineral output during the menstrual cycle.
AID  - 10.1136/bjsm.21.1.9
DP  - 1987 Mar 01
TA  - British Journal of Sports Medicine
PG  - 9--12
VI  - 21
IP  - 1
4099  - http://bjsm.bmj.com/content/21/1/9.short
4100  - http://bjsm.bmj.com/content/21/1/9.full
SO  - Br J Sports Med1987 Mar 01; 21
AB  - This study monitors changes in urinary excretion of water and minerals before and after exercise in pre-menopausal women and in those using oral contraception. Resting urine flow rate was lower and sodium output significantly higher (p less than 0.02) during the normal post-menstrual phase than during other phases of the cycle. These changes were unrelated to glomerular filtration rate and might impede maximal performance. After exercise an oliguria and hyponatriuresis were most pronounced during the menstrual phase. In addition the resting urinary output of calcium and magnesium were unrelated to normal oestrogenic and progestegenic cyclic surges. Amongst oral contraceptive users, resting excretion of water, minerals and creatinine were all significantly lower than general menstrual cycle values (p less than 0.01) and further reductions in salts and water output occurred with exercise. Basal calcium and magnesium excretion rates were significantly lower than general menstrual cycle values (p less than 0.05). Renal conservation of water and salts for 'pill' takers may affect renal homeostasis. The consequences of mineral retention are unknown.