It has long been established that sitting for too many hours per day is bad for our health. Excessive sitting is indicative of a sedentary lifestyle, against which doctors have been warning us for many, many years. Sitting too much is tied to high blood pressure, high blood sugar (and therefore diabetes), cardiovascular illness and excess body fat.

A new study published in the National Academy of Sciences has found yet another reason to spend more time on our feet and keep moving: too much sitting can actually change the shape of our hearts. For the study (which is primarily about how the human heart has evolved over time), researchers employed ultrasound imaging to analyze the hearts of about 160 men. The participants for separated out into four different categories: endurance runners, American football linemen (many of whom are technically overweight), American Indian farmers from the Tarahumara tribe, and ordinary sedentary adults.

When examining the men’s hearts, researchers paid special attention to the left ventricle, the left lower chamber of the human heart. The left ventricle receives blood from the left atrium and pumps it back out through the aorta.

The shape of the particpants’ hearts varied depending on which group they belonged to. For example, long-distance runners and Tarahumara farmers were found to have long ventricles and thin walls. On the other hand, the football linemen and sedentary individuals had shorter, wider ventricles and thicker walls. In other words, their hearts were of a rounder shape, similar to the hearts of chimpanzees. While the linemen’s hearts are thought to have developed this shape in order to adapt to the demands of their sport (brief, intense efforts), sedentary people appear to have rounder hearts owing to a want of physical exercise. Here’s an excerpt from the study:

“Specifically, we found, in relatively young disease-free men, that the absence of routine moderate-intensity EPA [endurance physical activity] is associated with a shift toward an apelike LV [left ventricular] phenotype which occurs independently of hypertension. As corroborated by abundant data on the effects of physical activity on the cardiovascular system, EPA beginning early in life and maintained into old age helps to maintain normal BP [blood pressure].

“Our data further emphasize the cardiovascular importance of regular EPA by showing that the maintenance of the derived human LV phenotype may also require routine bouts of moderate-intensity EPA across the life span. Thus, the independent and combined effects of routine lifelong moderate EPA on the derived LV and arterial BP may help to reduce the corollary risk of hypertensive heart disease.”

Translation: stay active.