Short-Term Magnesium Supplementation Has Modest Detrimental Effects on Cycle Ergometer Exercise Performance and Skeletal Muscle Mitochondria and Negligible Effects on the Gut Microbiota: A Randomized Crossover Clinical Trial

Bomar, Matthew C.; Ewell, Taylor R.; Brown, Reagan L.; Brown, David M.; Kwarteng, Beatrice S.; Abbotts, Kieran S. S.; Butterklee, Hannah M.; Williams, Natasha N. B.; Wrigley, Scott D.; Walsh, Maureen A.; Hamilton, Karyn L.; Thomson, David P.; Weir, Tiffany L.; Bell, Christopher

doi:10.3390/nu17050915

Open AccessArticle

Short-Term Magnesium Supplementation Has Modest Detrimental Effects on Cycle Ergometer Exercise Performance and Skeletal Muscle Mitochondria and Negligible Effects on the Gut Microbiota: A Randomized Crossover Clinical Trial

by

Matthew C. Bomar

¹,

Taylor R. Ewell

¹,

Reagan L. Brown

¹,

David M. Brown

¹,

Beatrice S. Kwarteng

¹,

Kieran S. S. Abbotts

¹

,

Hannah M. Butterklee

¹,

Natasha N. B. Williams

²,

Scott D. Wrigley

²,

Maureen A. Walsh

¹

,

Karyn L. Hamilton

¹

,

David P. Thomson

¹

,

Tiffany L. Weir

^2,*

and

Christopher Bell

^1,*

¹

Department of Health and Exercise Science, Colorado State University, Fort Collins, CO 80523-1582, USA

²

Department of Food Science and Human Nutrition, Colorado State University, Fort Collins, CO 80523-1571, USA

^*

Authors to whom correspondence should be addressed.

Nutrients 2025, 17(5), 915; https://doi.org/10.3390/nu17050915

Submission received: 15 February 2025 / Revised: 28 February 2025 / Accepted: 2 March 2025 / Published: 6 March 2025

(This article belongs to the Special Issue Nutritional Supplementation in Health and Sports Performance)

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Abstract

Background/Objectives: Although the importance of magnesium for overall health and physiological function is well established, its influence on exercise performance is less clear. The primary study objective was to determine the influence of short-term magnesium supplementation on cycle ergometer exercise performance. The hypothesis was that magnesium would elicit an ergogenic effect. Methods: A randomized, double-blind, placebo-controlled, two-period crossover design was used to study men and women who were regular exercisers. Fifteen participants ingested either a placebo or magnesium chloride (MgCl₂ 300 mg) twice per day, for 9 days, separated by a 3-week washout. During days 8 and 9, participants completed a battery of cycle ergometer exercise tests, and whole blood, vastus lateralis, and stools were sampled. The primary outcomes were the maximal oxygen uptake (VO_2max), a simulated 10 km time trial, and the sprint exercise performance. Additional outcomes included skeletal muscle mitochondrial respiration, and, on account of the known laxative effects of magnesium, the gut microbiota diversity. Results: Compared with a placebo, MgCl₂ supplementation increased the circulating ionized Mg concentration (p < 0.03), decreased the VO_2max (44.4 ± 7.7 vs. 41.3 ± 8.0 mL/kg/min; p = 0.005), and decreased the mean power output during a 30 s sprint (439 ± 88 vs. 415 ± 88 W; p = 0.03). The 10 km time trial was unaffected (1282 ± 126 vs. 1281 ± 97 s; p = 0.89). In skeletal muscle, MgCl₂ decreased mitochondrial respiration in the presence of fatty acids at complex II (p = 0.04). There were no significant impacts on the gut microbiota richness (CHAO1; p = 0.68), Shannon’s Diversity (p = 0.23), or the beta-diversity (Bray–Curtis distances; p = 0.74). Conclusions: In summary, magnesium supplementation had modest ergolytic effects on cycle ergometer exercise performance and mitochondrial respiration. We recommend that regular exercisers, free from hypomagnesemia, should not supplement their diet with magnesium.

Keywords: ergolytic; dietary supplement; maximal oxygen uptake; time trial; gastrointestinal microbiome

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MDPI and ACS Style

Bomar, M.C.; Ewell, T.R.; Brown, R.L.; Brown, D.M.; Kwarteng, B.S.; Abbotts, K.S.S.; Butterklee, H.M.; Williams, N.N.B.; Wrigley, S.D.; Walsh, M.A.; et al. Short-Term Magnesium Supplementation Has Modest Detrimental Effects on Cycle Ergometer Exercise Performance and Skeletal Muscle Mitochondria and Negligible Effects on the Gut Microbiota: A Randomized Crossover Clinical Trial. Nutrients 2025, 17, 915. https://doi.org/10.3390/nu17050915

AMA Style

Bomar MC, Ewell TR, Brown RL, Brown DM, Kwarteng BS, Abbotts KSS, Butterklee HM, Williams NNB, Wrigley SD, Walsh MA, et al. Short-Term Magnesium Supplementation Has Modest Detrimental Effects on Cycle Ergometer Exercise Performance and Skeletal Muscle Mitochondria and Negligible Effects on the Gut Microbiota: A Randomized Crossover Clinical Trial. Nutrients. 2025; 17(5):915. https://doi.org/10.3390/nu17050915

Chicago/Turabian Style

Bomar, Matthew C., Taylor R. Ewell, Reagan L. Brown, David M. Brown, Beatrice S. Kwarteng, Kieran S. S. Abbotts, Hannah M. Butterklee, Natasha N. B. Williams, Scott D. Wrigley, Maureen A. Walsh, and et al. 2025. "Short-Term Magnesium Supplementation Has Modest Detrimental Effects on Cycle Ergometer Exercise Performance and Skeletal Muscle Mitochondria and Negligible Effects on the Gut Microbiota: A Randomized Crossover Clinical Trial" Nutrients 17, no. 5: 915. https://doi.org/10.3390/nu17050915

APA Style

Bomar, M. C., Ewell, T. R., Brown, R. L., Brown, D. M., Kwarteng, B. S., Abbotts, K. S. S., Butterklee, H. M., Williams, N. N. B., Wrigley, S. D., Walsh, M. A., Hamilton, K. L., Thomson, D. P., Weir, T. L., & Bell, C. (2025). Short-Term Magnesium Supplementation Has Modest Detrimental Effects on Cycle Ergometer Exercise Performance and Skeletal Muscle Mitochondria and Negligible Effects on the Gut Microbiota: A Randomized Crossover Clinical Trial. Nutrients, 17(5), 915. https://doi.org/10.3390/nu17050915

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Short-Term Magnesium Supplementation Has Modest Detrimental Effects on Cycle Ergometer Exercise Performance and Skeletal Muscle Mitochondria and Negligible Effects on the Gut Microbiota: A Randomized Crossover Clinical Trial

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