Effect of heat exposure and physical exercise until exhaustion in normothermic and hyperthermic conditions on serum, sweat and urinary concentrations of magnesium and phosphorus.
Level 3 - non-randomized controlled study
Non-randomized controlled study (randomization not specified).
PubMed 31466751 · doi:10.1016/j.jtherbio.2019.07.010
What was done
Twenty-nine male university students were allocated to an experimental group (n = 15) or a control group (n = 14). Both groups performed an incremental cycle ergometer exercise test until exhaustion under normothermic (22 °C) and hyperthermic (42 °C) conditions before and after an intervention period. The experimental group completed 9 sauna heat acclimation sessions (100 °C), while the control group did not. Urine and blood samples were collected before and after each trial, and sweat was sampled after hyperthermic tests. Magnesium (Mg) and phosphorus (P) concentrations were quantified using ICP-MS.
What was found
No absolute numerical concentrations were reported in the abstract, only statistical significance and directions of effect: - Post-exercise serum Mg decreased in both groups pre-acclimation, but post-acclimation a post-exercise decrease in serum Mg occurred only in the experimental group (p < .01). - Urinary Mg excretion was unaffected prior to acclimation, but the experimental group exhibited an increase in urinary Mg excretion post-exercise following acclimation (p < .01). - Sweat Mg loss during hyperthermic exercise significantly decreased following heat acclimation in the experimental group (p < .05). - Phosphorus status remained largely unchanged, except for an increase in post-exercise urinary P excretion after the normothermic trial post-acclimation (p < .05).
Why it matters
This study suggests that heat acclimation shifts the route of magnesium clearance during exercise in hot environments from sweat to urine, indicating altered mineral handling during thermal adaptation.
Limits
The study evaluated a small sample of exclusively male university students (n = 29), limiting generalizability to females and other age or fitness groups. Randomization was not specified. The abstract lacks baseline and follow-up absolute numerical values, standard deviations, and information regarding dietary mineral intake controls.
Cited by
- supports Athletes and heavy sauna users require approximately 10% to 20% more magnesium than the RDA due to losses in sweat and urine.