Athletic Mice Run Less After Taking Antibiotics

Researchers in California have conducted a mouse study that suggests the killing of essential gut bacteria following antibiotic use can negatively impact the motivation and endurance of athletes. The findings may point to a microbiome-based explanation for why some individuals are couch potatoes while others excel at athletics.

“We believed an animal’s collection of gut bacteria, its microbiome, would affect digestive processes and muscle function, as well as motivation for various behaviors, including exercise,” says Theodore Garland, an evolutionary physiologist at University of California – Riverside (UCR). “Our study reinforces this belief.”

Garland and colleagues gave two sets of mice—one of which was bred for high levels of running—a 10-day course of antibiotics and confirmed through fecal samples that gut bacteria were reduced in both. Neither group of mice exhibited any signs of sickness from the antibiotic treatment.

Though the behavior of the normal mice was not signicantly affected during or after treatment, the athletic mice ran their wheels 21% less and did not recover their running behavior even 12 days after the antibiotic treatment stopped.

The team is certain the microbiome damage was responsible, comparing the knockout of the normal gut microbiome to an injury. “A casual exerciser with a minor injury wouldn’t be affected much. But on a world-class athlete, a small setback can be much more magnified,” says Monica McNamara, UCR evolutionary biology doctoral student. “That’s why we wanted to compare the two types of mice.”

One way the microbiome might affect exercise in mice or in humans is through its ability to transform carbohydrates into chemicals that travel through the body and affect muscle performance. “Metabolic end products from bacteria in the gut can be reabsorbed and used as fuel,” Garland said. “Fewer good bacteria means less available fuel.”

Moving forward, the researchers would like to identify the specific bacteria responsible for increased athletic performance. “If we can pinpoint the right microbes, there exists the possibility of using them as a therapeutic to help average people exercise more,” Garland said.

A lack of exercise is known to be a major risk factor for aspects of mental health, including depression, as well as physical health, including metabolic syndrome, diabetes, obesity, cardiovascular disease, cancer, and osteoporosis. Many in the public health community would like to promote exercise, but few have found ways to do it successfully.  “Though we are studying mice, their physiology is very similar to humans. The more we learn from them, the better our chances of improving our own health,” Garland said. 

Certain foods may also increase desirable gut bacteria. While research into "probiotics" is developing, Garland recommends that those interested in promoting overall health maintain a balanced diet in addition to regular exercise.

“We do know from previous studies that the western diet, high in fat and sugar, can have a negative effect on biodiversity in your gut and likely, by extension, on athletic ability and possibly even on motivation to exercise,” Garland said.

The findings are detailed in a recent issue of the journal Behavioural Processes.