Effect of acute high-intensive swimming exercise on blood electrolytes and metabolites

Magnesium (Mg²⁺) is an essential co-factor for over 325 physiological and biochemical processes so that plays a central role of neuronal activity, cardiac excitability, neuromuscular transmission, muscular contraction, vasomotor tone, and blood pressure significantly related to physical performance. However, only limited information on blood ionized Mg²⁺ (iMg²⁺) regarding to physical exercise is available and the data from blood total Mg²⁺ detection are inconsistent. This present study investigated the changes of blood iMg²⁺ correlated with metabolic demands during acute high-intensive exhaustive physical exercise in rats. After exhausted swimming (3-4 hours), blood pH, glucose, HCO₃^-, oxygen and ionized Ca²⁺ (iCa²⁺) were significantly decreased, whereas lactate, carbon dioxide, iMg²⁺, ionized Na⁺ and ionized K⁺ were significantly increased. During the exhausted swimming, the changes in iMg²⁺ showed a significant negative correlation with changes in pH, glucose, HCO₃^- and iCa²⁺, however a significant negative correlation with changes in lactate and anionic gap. It is concluded that the acute high-intensive exhaustive physical exercise could produced hypermagnesemia, an increase in blood iMg²⁺ via stimulation of iMg²⁺ efflux following increase in intracellular iMg²⁺ from muscle induced by metabolic and respiratory acidosis.