Big quote: In a new study, researchers are uncovering the profound impact of exercise on the human body, revealing it to be “the single most potent medical intervention ever known,” according to Dr. Euan Ashley, professor of cardiovascular medicine and genetics at Stanford University. While the positive effects of exercise have been known for decades, this research aims to create a molecular map of exercise benefits.

As millions of Americans embark on their New Year’s resolutions to exercise more, a scientific consortium led by Stanford is shedding light on the intricate ways physical activity benefits our health.

Dr. Ashley, who was recently named chair of Stanford’s Department of Medicine, spoke with William Brangham on PBS NewsHour about the study’s findings. “We have known for maybe 70 years that exercise was among one of the most potent medical interventions known,” Ashley explained. He cited a study from the 1950s comparing London bus drivers and conductors, which found that the heart disease rate among the sedentary drivers was twice that of the more active conductors.

The current research, however, goes far beyond these early observations. By bringing together 17 to 18 different groups from across the United States, the MoTrPAC study aims to explain how exercise works at the most fundamental level.

The initial findings have been nothing short of remarkable, Dr. Ashley said.

In one experiment, researchers studied rats that underwent eight weeks of aerobic training on a treadmill. “Every single tissue we looked at showed something completely different from before,” he reported. “It really changed the entire molecular makeup of the individual organs of the rats in a very positive direction.”

One of the most intriguing discoveries was how exercise seemed to counteract disease-related changes in the body. “When we looked at the changes with exercise, we often saw mirror image changes to the ones we see with disease,” Dr. Ashley said. This observation suggests that exercise may be actively reversing some of the molecular changes associated with various illnesses.

The study’s scope extended far beyond the expected impacts on heart and skeletal muscle. Researchers observed significant changes in the kidney, adrenal gland, intestine, and brain. This wide-ranging effect helps explain why exercise is associated with numerous health benefits, from reducing the risk of heart disease and various cancers by 50 percent to improving sleep, mood, and respiratory function.

Dr. Ashley posits that the key to exercise’s effectiveness lies in its nature as a controlled stress on the body. “I think that stressing our bodies with exercise in just the right amount actually prepares our bodies to deal with the stress of everyday life,” he explained.

One significant finding was the activation of the heat-shock response across multiple tissues. This system helps proteins in cells maintain their proper three-dimensional structure and prevents them from aggregating inappropriately.

The study also revealed surprising gender differences in the response to exercise. Both at rest and during physical activity, male and female rats showed profound variations, particularly in adipose tissue and skeletal muscle. These findings underscore the importance of including both sexes in future studies to adequately describe the effects of exercise for everyone.

For those wondering about the practical implications of this research, Dr. Ashley offers some guidance based on existing knowledge. “Any movement is better than none,” he said. For people with sedentary jobs, simply standing up and taking a walk during lunch can be beneficial. Ideally, adults should aim for 30 to 45 minutes of moderate-intensity exercise, such as a brisk walk, five to six times a week.

Dr. Ashley, who is also a practicing cardiologist, often tells his patients, “One minute of exercise buys you five minutes of extra life.” This compelling statistic increases to seven or eight minutes of extra life for higher-intensity exercise. He reassures that the timing of exercise is flexible – morning, lunchtime, or evening are all beneficial, with post-meal exercise being particularly effective.