3 minutes of intense physical effort had more impact than 90 minutes of moderate exercise

A few minutes of intense physical activity may cause the body to react very differently than a moderate workout lasting an hour and a half. Researchers from Rockefeller University found that just six 30-second sprints — three minutes of cumulative effort — caused extensive changes in proteins and other substances found in the blood immediately after the workout. In contrast, after 90 minutes of continuous cycling at moderate intensity, a much more limited immediate response was recorded.

Researchers wanted to understand how the intensity of activity affects the processes that occur in the body following a workout. To do this, they compared several types of activity. In the intense workout, participants performed six 30-second sprints, meaning three minutes of maximum effort in total. Conversely, moderate and prolonged activity was also tested, which included 90 minutes of continuous cycling.

The results showed a large gap. Immediately after the sprints, almost a quarter of the proteins measured in the blood changed. After 90 minutes of moderate cycling, however, the change was recorded in less than a quarter of a percent of them. Moderate running on a treadmill also affected a larger number of proteins compared to cycling, but still much less than the short sprints. It is important to emphasize: the study does not say that three minutes of sprinting is "equal" to 90 minutes of moderate activity, but that they trigger a different and much stronger immediate biological response in the measured parameters.

Sprints affected not only proteins. Researchers also identified changes in more than 200 metabolites — small substances that are created or used in chemical processes occurring in the body. In addition, a rapid increase was recorded in proteins associated, among other things, with blood vessel growth, tissue changes, and hormonal signaling.

Some of the proteins reached the blood quickly through a mechanism where parts of proteins already on the surface of cells are "cut" and released into the bloodstream. That is, the body did not need to produce them again to create the rapid response.

Researchers sought to test whether the changes in the blood also affect other cells in the body. To do this, they exposed human fat cells to blood taken after the sprint workout. The result was an extensive change in the gene activity of those same cells. Among other things, processes related to how cells use energy sources, respond to hormones, and recognize the amount of nutrients available to them changed. When fat cells were exposed to blood taken after moderate cycling, the changes were much smaller.

The response to the moderate workout was not necessarily weaker in every sense — part of it simply appeared later. Researchers discovered that a significant increase in fatty acids and proteins originating from the liver, associated with the demands of prolonged endurance activity, appeared in the blood only about three hours after the end of the workout. That is, while the sprints triggered a fast and broad wave of changes, moderate activity led to a different response, part of which developed gradually.

In another stage, researchers compared the proteins that responded to physical activity with health information of more than 53,000 people from the UK Biobank database. Many of the proteins found in the study were associated with a lower risk of heart disease and metabolic problems. The gap was particularly prominent regarding obesity, type 2 diabetes, and other metabolic disorders. Out of 33 proteins linked to a lower risk of these conditions, 32 changed following the sprints, compared to only three that were affected by the moderate activity. More than a quarter of those same proteins were also linked to slower biological aging.

However, these links do not prove that sprints themselves will prevent diseases or extend life. They provide researchers with clues regarding the mechanisms through which intense activity may affect health.

According to researcher Cohen, "what is exciting here is that just a few minutes of intense activity can trigger a significant molecular response." According to him, the response continued to appear even after eight weeks of training. This means that it is probably not caused only by the body not being used to the effort. Researcher Luke Olsen explained that it is already known that training at different intensities causes the body to adapt in different ways, but the mechanisms behind these differences are still not fully understood.

According to him, the study indicates that proteins and metabolites released into the bloodstream after physical activity are very sensitive to the intensity of the effort — and it is possible that they play a central role in the health effects of short and vigorous activity.

The findings do not prove that three minutes of sprints provide all the benefits of 90 minutes of moderate activity, nor that intense training is superior in every health aspect. What the study does show is that the duration of the workout is not the only variable that matters. The intensity at which we train can also dramatically change the signals that the body sends through the bloodstream. Simply put: the body does not respond only to the question of how long we trained, but also to the question of how hard we exerted ourselves.