The Hearts and Guts of a Runner

It has been an exciting week for those who are interested in the science of running, and, in particular, how exercise affects our bodies.

Article last updated on March 9, 2021

It has been an exciting week for those who are interested in the science of running, and, in particular, how exercise affects our bodies. I believe we can all benefit from understanding our bodies. Not just with regards to training, but in our lives in general as well.

Hearts Fighting Gravity Work Harder

As such, this article marks the launch of a new column. The purpose is to share intriguing research at the cross section of physiology and running. This week I came across the results from two recent studies published. First up, The New York Times highlighted a study that looked at the physical differences in the hearts of elite runners and elite swimmers.

Runners, the researchers found, had larger and more efficient left ventricles than their swimming counterparts. Put more precisely, runners had left ventricles that filled with blood earlier and emptied more emphatically than the swimmers. One scientist theorised that gravity is the root cause:

Since swimmers exercise in a horizontal position, he says, their hearts do not have to fight gravity to get blood back to the heart, unlike in upright runners. Posture does some of the work for swimmers, and so their hearts reshape themselves only as much as needed for the demands of their sport.

The original study was titled Left Ventricular Structure and Function in Elite Swimmers and Runners and was authored by Currie et al.

Lactate Eating Minions Occupy the Guts of Runners

The other piece of research that caught my attention this week came from Scheiman et al. The paper has the catchy title Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism.

The one-sentence summary from this paper is that the researchers identified that a lactate eating bacteria, Veillonella, flourished in runners’ stomachs. Exploring further, they isolated and inserted this particular microbe into mice. Can you guess the results in a run to exhaustion test? The mice exposed to this particular microbe ran 13% longer.

Of course, there is no guarantee that the results will translate to humans. Or active runners, for that matter. So we have to wait a bit before we can pop up a can of probiotics containing Veillonella in the future to boost our running performances. Speaking to NPR, which published an excellent article on the study, one of the researchers said:

Athletes that exercise often may simply be creating a gut with higher levels of lactate that allow Veillonella to flourish

Regardless, the results are grounds for further research. And, simultaneously, the results also seem to indicate another important implication. It is possible to train our bodies to become more efficient at using lactate as a source of energy.

Like this article?

Join 700+ runners who get our weekly newsletter about running in their inboxes every Monday morning!

By Lars-Christian Simonsen

Lars-Christian is the founder of Run161. He characterises himself as a student of the sport who is always looking to learn more.