Microbiota and training: inflammation, recovery, and performance

They say “the gut is the second brain.” That’s cute, but incomplete.
In reality, it’s also a coach, a physical trainer, a logistician, and sometimes… a silent saboteur.
(If the gut wore shoes, it would probably choose Vibrams, because “ground connection is life.”)

We train to improve our performance, our well-being, and our energy.
And yet, many regular athletes feel the opposite:
chronic fatigue, slow recovery, stagnation, or even loss of motivation — even though “everything is done correctly.”

An unpleasant surprise?
It’s not always the muscle or the nervous system that’s the problem, but a forgotten organ working undercover: the gut microbiota.

Depending on how you train, eat, and recover, this ecosystem can boost your adaptation… or trigger silent inflammation that slows your progress, without pain or obvious signs, just that “hey, I’m not progressing anymore despite my efforts” feeling.

Which raises a simple but unsettling question:
👉 What if your performance wasn’t determined in your muscles, but in your gut?

The gut microbiota is not static. It can evolve—depending on diet, lifestyle… and physical activity. Several studies show that regular training, even moderate, is associated with greater microbial diversity (Varghese, S., 2024).

This microbial diversity is a bit like a reserve of “bacterial good vibes”: more species = more metabolic, immune, and digestive functions available.

And exercise seems to foster this richness.

One of the key functions of the microbiota: producing essential metabolites — especially short-chain fatty acids (SCFAs) such as butyrate, propionate, and acetate.

These compounds play a role in:

• intestinal mucosal health
  
  

• inflammation regulation
  
  

• metabolism
  
  

• recovery
  
  

In short, everything that contributes to sustainable performance (Mailing, L.J., 2019).

When training is intense, prolonged, in the heat, or involves dehydration, the intestinal barrier can be compromised: the mucosa weakens, the junctions “open,” protective mucus decreases—and compounds like endotoxins (LPS) can enter the bloodstream.

Result: systemic, often invisible inflammation: fatigue, slowed recovery, decreased performance (Dmytriv, T.R., 2024).

Several aggravating factors contribute to altering the balance of the microbiota and compromising physical performance.

• long/high-volume exercise
  
  

• heat and dehydration
  
  

• fiber-poor diet
  
  

• frequent consumption of ultra-processed foods
  
  

• lack of recovery

A context that, when combined, can create a pro-inflammatory environment unfavorable to performance.

💡 These mechanisms — heat, dehydration, thermal stress, redistribution of blood flow, intestinal permeability — are explored in detail in our article:
👉 Hyperthermia, Dehydration and Performance

This article shows how prolonged exertion in extreme thermal conditions can trigger major physiological disturbances, including:

• hyperthermia
  
  

• decreased plasma volume
  
  

• digestive ischemia
  
  

• hormonal disturbance
  
  

• cognitive impairment
  
  

• risk of increased intestinal permeability
  
  

This link between thermal stress and gut health places the gut at the heart of performance.

“If I don’t have a stomach ache, my gut is healthy.”

Reality: Intestinal permeability can increase without digestive symptoms. Inflammation, however, manifests as fatigue, slow recovery, stagnation.

“The microbiota is just about diet.”

 Reality: Training directly modifies the microbiota — its composition, diversity, and metabolism.

“Performance = muscle + mental.”

Reality: Performance = muscle + mental + gut. And the third is often the weak link.

This “silent inflammation” — even when moderate — can affect:

• recovery
  
  

• adaptation
  
  

• metabolism
  
  

• energy
  
  

• training resistance
  
  

It is not as spectacular as an injury — but it is remarkably effective at sabotaging your progress (Varghese, S., 2024).

The microbiota and the gut communicate with the brain via the gut-brain axis.

This link influences:

• mood
  
  

• stress
  
  

• motivational fatigue
  
  

A “tired” or dysbiotic gut can undermine the motivation to train, regardless of willpower (Dmytriv, T.R., 2024).

• avoiding the "volume + heat + dehydration" combination

• taking hydration and recovery into account
  
  

• avoiding prolonged fasted training
  

A varied diet including different food groups can help support a balanced microbiota and limit certain pro-inflammatory factors.

• Fiber (vegetables, legumes, fruits, whole grains)
  
  

• Omega-3s (fatty fish, seeds, nuts)
  
  

• Polyphenols (fruits, vegetables, tea, cocoa)
  
  

• Fermented foods (depending on tolerance)
  
  

And above all:

• limit ultra-processed foods (ready meals, snacks, sodas, refined oils, additives), which are pro-inflammatory and harmful to the microbiota.

Regularly adopting these habits can contribute to a more stable gut environment, favorable to well-being and performance over time.

1. 500–700 ml of water + electrolytes before a long/intense session
   
   

2. Vegetables + a source of omega-3s at every meal
   
   

3. Avoid ultra-processed foods before/after training

The gut microbiota, the intestinal barrier, inflammation, and performance are not separate elements.
They form an integrated system.

Training the body also means training the inner ecosystem.

Protecting the gut means investing in:

• recovery
  
  

• resilience
  
  

• longevity
  
  

• sustainable performance
  
  

👉 Muscles don't train alone. They train with the gut and influence the quality of the microbiota.

• Varghese, S. (2024). Physical Exercise and the Gut Microbiome: A Bidirectional Relationship Influencing Health and Performance. Nutrients, 16(21), 3663. https://doi.org/10.3390/nu16213663

• Dmytriv, T.R. (2024). Intestinal barrier permeability: the influence of gut microbiota, nutrition and exercise. Frontiers in Physiology. https://doi.org/10.3389/fphys.2024.1380713

• Mailing, L.J., Allen, J.M., Buford, T.W., et al. (2019). Exercise and the Gut Microbiome: A Review of the Evidence, Potential Mechanisms, and Implications for Human Health. Exercise and Sport Sciences Reviews, 47(2):75–85. https://doi.org/10.1249/JES.0000000000000183

• Cullen, J.M.A., Shahzad, M., Dhillon, S. (2023). A systematic review on the effects of exercise on gut microbial composition and function in humans and animals. Frontiers in Physiology. https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2023.1292673

• Yoon, E.J., et al. (2024). Effect of long-term endurance exercise on gut health, inflammation and intestinal barrier in non-athletes. International Journal of Molecular Sciences, 25(19):10742. https://doi.org/10.3390/ijms251910742

• Aya, V., et al. (2023). Effects of exercise and physical activity on gut microbiota in older adults: a systematic review. BMC Geriatrics. https://doi.org/10.1186/s12877-023-04066-y