All that to say, in mice trials, their gut microbiome is completely, or near completely depleted, while Mike’s client still maintained at least a portion of her gut microbiome.
There are approximately 100 trillion bacteria in the gut microbiome. While Cephalexin may be strong enough to cause some adverse reactions, it does not knock out the entire population of little critters in your colon.
At the same time, we haven’t yet identified all the potential microbes responsible for modulating exercise.
We have seen Veillonella correlate to improved endurance performance metrics through metabolizing lactate to propionate (5). Eubacterium rectale positively affects swimming to exhaustion, both with and without training intervention (6).
However, much outside of that, we don’t understand what specific strains of bacteria are modulating exercise. We don’t know which strains are upregulating or downregulating short chain fatty acids or other gut derived metabolites that may be linked to exercise performance.
Furthermore, there is conflicting data on which short chain fatty acids contribute to exercise performance and we don’t know if the Cephalexin knocked those specific bacteria out. This could be a massive factor in the current design of the animal model trials, which does not match the human model, where antibiotics are prescribed for a specific infection.
That, with no other contributing material, is enough to cause a discrepancy.
But don’t fret, there is more that I didn’t think of.
Dr. Campbell also educated me about sex differences affecting exercise tolerance in mice and how that could contribute to the differences we saw in mice and Dr. Mike’s client data.
In McNamara 2022 and Valentino 2021, we see that running distance and volume were not altered in control mice that received antibiotic treatment. The mice studied in these two studies were female (2, 4).
However, in Nay 2019 and Okamoto 2019, when male mice are treated with antibiotics, there is a decrease in running endurance. Interestingly, Nay allowed the mice to naturally reseed, restoring their gut microbiota.
Natural reseeding occurred by receiving twice soiled litter from the control group’s cages and the process restored running endurance (3). Ew! But this makes it clear that the status of the gut microbiome played a significant role in running endurance.
So, the fact that Dr. Mike’s client was female, could be playing a role in some discrepancies depending on what data was initially reviewed and compared.
However, I’m going to take away a win from this experience.
The one thing that Dr. Campbell and I agreed on is that the psychology of Dr. Mike’s client could have played a pivotal role in her exercise performance, muddying the data a little bit more.
The 5K Rower Challenge
It’s common knowledge that high performers like a challenge.
Dr. Mike’s client is just that. Her 5K time is currently in the 87th percentile in the world, which is no joke!
When athletes’ backs are against the wall and know they have a challenge in front of them, they want to go against the grain and perform. Think of Michael Jordan in Game 5 of the 1997 NBA Finals.
There was no placebo in this experiment. Dr. Mike’s client knew that she had taken the antibiotics, she knew it could affect her performance, and she knew her pace throughout the entire time trial.
When mice undergo exercise testing, they have no clue what they are doing or have any emotional attachment to their time.
Psychology and physiology go hand in hand. It’s one of the core tenants of Dr. Mike’s Flex Diet Certification. I knew that this would be a confounding variable in the comparison of mice data and human data.
Summary of Antibiotics and Human Exercise Performance
In this n = 1 experiment, it seems that 10 days of antibiotic treatment does not affect aerobic capacity in our human female subject despite some animal data showing negative effects.
Paul Buono is a self-employed strength and conditioning and nutrition coach with 12 years of coaching experience. Paul has trained and competed at a high level in CrossFit. In 2015, he took 2nd place at the CrossFit Games with CrossFit Milford. In recent years, a Lupus diagnosis has shifted his focus from coaching high-level athletes to individuals with autoimmune diseases. Paul is finishing his M.S. in Kinesiology and Applied Physiology at Rutgers University-New Brunswick in Spring 2023. He uses his education and experience to help his clients live incredible and fulfilling lives despite their diagnoses.
1. Okamoto, T., Morino, K., Ugi, S., Nakagawa, F., Lemecha, M., Ida, S., et al. (2019). Microbiome potentiates endurance exercise through intestinal acetate production. Am. J. Physiol. Endocrinol. Metab. 316, E956–E966. doi: 10.1152/ ajpendo.00510.2018
2. McNamara, M. P., Cadney, M. D., Castro, A. A., Hillis, D. A., Kallini, K. M., Macbeth, J. C., Schmill, M. P., Schwartz, N. E., Hsiao, A., & Garland, T., Jr (2022). Oral antibiotics reduce voluntary exercise behavior in athletic mice. Behavioural processes, 199, 104650. https://doi.org/10.1016/j.beproc.2022.104650
3. Nay, K., Jollet, M., Goustard, B., Baati, N., Vernus, B., Pontones, M., Lefeuvre-Orfila, L., Bendavid, C., Rué, O., Mariadassou, M., Bonnieu, A., Ollendorff, V., Lepage, P., Derbré, F., & Koechlin-Ramonatxo, C. (2019). Gut bacteria are critical for optimal muscle function: a potential link with glucose homeostasis. American journal of physiology. Endocrinology and metabolism, 317(1), E158–E171. https://doi.org/10.1152/ajpendo.00521.2018
4. Valentino, T. R., Vechetti, I. J., Jr, Mobley, C. B., Dungan, C. M., Golden, L., Goh, J., & McCarthy, J. J. (2021). Dysbiosis of the gut microbiome impairs mouse skeletal muscle adaptation to exercise. The Journal of physiology, 599(21), 4845–4863. https://doi.org/10.1113/JP281788
5. Scheiman, J., Luber, J. M., Chavkin, T. A., MacDonald, T., Tung, A., Pham, L. D., Wibowo, M. C., Wurth, R. C., Punthambaker, S., Tierney, B. T., Yang, Z., Hattab, M. W., Avila-Pacheco, J., Clish, C. B., Lessard, S., Church, G. M., & Kostic, A. D. (2019). Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism. Nature medicine, 25(7), 1104–1109. https://doi.org/10.1038/s41591-019-0485-4
6. Huang, W. C., Chen, Y. H., Chuang, H. L., Chiu, C. C., & Huang, C. C. (2019). Investigation of the Effects of Microbiota on Exercise Physiological Adaption, Performance, and Energy Utilization Using a Gnotobiotic Animal Model. Frontiers in microbiology, 10, 1906. https://doi.org/10.3389/fmicb.2019.01906
7. Herman TF, Hashmi MF. Cephalexin. [Updated 2022 Aug 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549780/