Intense exercise, bone structure and blood calcium levels in vertebrates


Sudden, large-scale fluctuations of systemic calcium concentrations are believed to be harmful to vertebrates. Consequently, it is generally accepted that vertebrates relatively closely monitor and regulate the calcium levels in blood and other tissues1, often by endocrinological mechanisms which act over long time periods to promote calcium deposition on or dissolution from bone2,3. However, after intense bouts of maximal activity, virtually all vertebrates experience a significant reduction in blood pH as a result of concomitant increases in blood P C O 2 and lactate concentrations4,5, and this might be expected to have wide-ranging physiological effects. We now present evidence that (1) blood plasma calcium concentrations rise abruptly and significantly as a result of intense muscular activity in all vertebrates investigated which have osseous skeletons, but not those with cartilaginous skeletons, and (2) the source of the excess calcium is bone.

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