FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-68/04

Title and Subtitle: Contribution of activity to the circadian rhythm in excretion of magnesium and calcium

Report Date: March 1968

Authors: Fiorika V, Burr MJ, Moses R

Abstract: Eight subjects were maintained on a standard dietary regimen ingested every four hours for 120 hours. Measurements of the magnesium and calcium excretion in these subjects revealed a circadian periodicity with maximal levels of excretion for both ions occurring during the sleeping hours (2200-0600) and minimal levels occurring during the mid-day (1000-1400). Further studies on the effects of activity (exercise) on the excretion of magnesium and calcium demonstrated a marked decrease during and following exercise accompanied by no significant change in the plasma concentrations of the two ions.

These data suggest that the periodicity in excretion reported here reflects an activity cycle generated by alternated periods of sleeping and waking and may not represent an endogenous rhythm of magnesium and calcium excretion.

Key Words: Magnesium, calcium, excretion, biological rhythms, exercise (physiology), diet, blood chemistry

No. of Pages: 8