Writing in the International Journal of Sport Nutrition and Exercise Metabolism, the research team believe the findings could lead to a 'personalised exercise prescription' that is designed to improve gut and overall health.
“We're not there yet," said study researcher Ryan Durk from San Francisco State University. "But this helps create that foundation."
According to Durk, the research reinforces the idea of "exercise as medicine, in which exercise is crucial for increasing beneficial bacteria in the gut".
With low microbiome diversity linked to insulin resistance and inflammation, as well as gastrointestinal (GI) conditions and even colorectal cancer, many have suggested that gut microbe communities could fast become a reliable indicator of overall health.
Research in recent years has looked to understand and develop approaches to promote overall GI health through shaping gut diversity to improve the status of dysbiosis-associated disorders.
One study of note found professional rugby players had a higher diversity of gut microorganisms compared to control subjects.
However, the Ireland-based team also found that the extreme dietary differences of these athletes, especially high protein intakes, interfered with interpretations regarding the specific role of physical activity and microbial changes.
Along with Jimmy Bagley, an assistant professor of kinesiology at San Francisco State University, Durk enrolled 21 males and 19 females aged around 26 years old, who did not take antibiotics in the 6 months leading up to the trial.
Participants completed a three-month exercise recall, tracked their nutritional intake for seven days and collected their stool sample. Body composition and maximal cardiorespiratory fitness (VO2max) were also measured.
Relative microbiota composition was determined from the stool samples that specifically measured the amount of the target gene, 16s RNA, which is found in the bacterial strains Firmicutes and Bacteroidetes.
Results indicated that participants with the best cardiovascular fitness had a higher firmicutes to bacteroides ratio.
While most gut bacteria can be beneficial (even bacteroides in some cases), firmicutes bacteria are associated with metabolic by-products that help prevent bacteria in the gut from leaking into the body.
Likely mechanisms of action
“These byproducts help strengthen the intestinal lining and help prevent leaky gut syndrome," said Durk.
“Future investigations should investigate the utility of exercise training as medium to promote beneficial changes in gut microbiota,” the study added.
The findings from this study and other studies point towards a series of proposed mechanisms that try to explain how physical activity enriches the gut bacterial community.
One theory identifies physically active individuals’ propensity to spend more time outdoors combining a healthy lifestyle and thus developing a more robust and richer microbiota.
At the same time, body adaptations to endurance-related exercise could lead to modifications in the GI tract.
Studies have illustrated this phenomenon via decreased blood flow, tissue hypoxia, and increased transit and absorptive capabilities.
These adaptive mechanisms amongst others could change the gut pH creating an environment favouring a richer community diversity.
Source: International Journal of Sport Nutrition and Exercise Metabolism
Published online ahead of print: DOI: 10.1123/ijsnem.2018-0024
“Gut Microbiota Composition is Related to Cardiorespiratory Fitness in Healthy Young Adults.”
Authors: Ryan P. Durk, et al