Disruptions in Calcium Homeostasis During High Intensity Exercise Under Different Ambient Conditions
MSSE May 2014 - Volume 46 - Supplement 1 5S Board #5 May 28, 9:30 AM - 11:30 AM Vanessa D. Sherk
Decreases in serum ionized calcium (iCa) and increases in parathyroid hormone (PTH) have been observed in response to exercise. It is not known whether the magnitude of dermal Ca
loss influences these changes.
PURPOSE: Determine whether dermal Ca loss during exercise is a determinant of the decline in iCa and increase in PTH.
METHODS: Women (n=14) and men (n=13) aged 18 to 45 years performed two 1-hour bouts of high intensity cycling at different ambient temperatures: 18 C and 28 C. The order of
the bouts was randomized and matched for power output. PTH and iCa were measured every 15 minutes from before to 1 hour after the end of exercise and were adjusted for plasma
volume shifts. Dermal Ca loss was estimated from sweat loss and sweat Ca concentration.
RESULTS: Dermal Ca loss was greater in the 28 C bout (33±20 vs. 23±17 mg, p<0.01; mean±SD); sweat Ca concentration was not different (28C: 3.5±1.3; 18C: 3.6±1.3 mg/dL). There was no difference between bouts in the changes in iCa and PTH from -6! to 60! or from 60! to 120!.
CONCLUSION: The decrease in iCa during exercise is a likely trigger for the increase in PTH. The magnitude of dermal Ca loss did not appear to influence the decline in iCa.
