Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
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SHR Neuro Krebs Kardio Lipid Stoffw Microb
Westmoreland, D; Anderson, D; Porta, S.
Effects of maximal and submaximal exercise on plasma electrolyte shifts
TRACE ELEM ELECTROLYTES. 2006; 23(4): 312-317.
Doi: 10.5414/TEP23312
Web of Science
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- Porta Sepp
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- Abstract:
- Background: Mineral fluctuations in the body have been extensively studied to determine effects on athletic performance, with magnesium in particular being the focus of many studies. As a general rule, high-intensity exercise induces an increase in plasma Mg, while submaximal exercise has the opposite effect. This generality is based on comparisons among studies that differed in subject pools and experimental design, however, and many exceptions to the general trend have been noted. In this study, we sought to control the effects of between-subject variability, exercise duration and time of day on the plasma Mg shift by having each subject take maximal and submaximal exercise trials at a standardized time of day within a 48-h period. Material and methods: 25 cadets of the United States Air Force Academy underwent both a submaximal cycle and a maximal-effort treadmill test in randomized order within a 48-h time period. Blood samples were drawn from each subject immediately before and after exercise and analyzed for whole blood Na, K, Mg, Ca, pH, PCO2, pO(2), HCO3-, base excess and hematocrit. Results: Submaximal exercise induced a significant change in K and Mg, while maximal exercise trials caused significant changes in all four measured electrolytes. The magnitude of electrolyte shifts was significantly different between trials for Na, Ca and Mg, and were in opposite directions for Ca and Mg. In both exercise regimens, there was a significant negative correlation between pre-exercise plasma Mg levels and the Mg shift during exercise. However, the thresholds that separated positive and negative Mg shifts were substantially different between the exercise regimens. Conclusion: Short exercise regimens differing in intensity have profound, and often opposite, effects on electrolyte shifts. This study supports the generality that high-intensity exercise leads to an increase in plasma Mg, while submaximal exercise leads to a decrease. Hypomagnesic individuals transfer Mg into the plasma compartment during exercise in proportion to workload. We hypothesize that the observed Mg rise in such individuals is a compensatory mechanism that involves rapid mobilization of Mg from apatite crystals in bone.
- Find related publications in this database (Keywords)
- plasma electrolytes
- Mg shift
- exercise physiology