Saying you don't have time to exercise is an argument that loses some merit when you learn how you can accomplish much more in less time. New research from Rockefeller University shows that just three minutes of all-out sprinting produced more dramatic changes in the molecular contents of the bloodstream than 90 minutes of continuous moderate exercise.

In the study, participants completed six 30-second, all-out sprints. Researchers found that this brief burst of intense exercise altered nearly a quarter of the proteins they measured immediately afterward. By comparison, 90 minutes of moderate, continuous cycling altered fewer than one-quarter of 1% of those proteins.

Moderate treadmill running produced more molecular changes than cycling, but still far fewer than the quick sprint workout.

The results suggest that when it comes to exercise, ore isn't necessarily better. The intensity of the exercise may play an important role in determining how the body responds.

The researchers wanted to see whether the changes occurring in the bloodstream after exercise could actually influence other tissues. To find out, they exposed human fat cells to blood collected from participants after they exercised and the results were striking.

Blood collected after sprinting caused extensive changes in gene activity within the fat cells. The cells changed the way they processed fuel, responded to hormones and sensed nutrient availability.

Moderate exercise produced a much smaller response. In fact, it wasn't until approximately three hours later that researchers observed a meaningful increase in fatty acids and liver-derived proteins typically associated with the body's response to endurance exercise. Fat cells exposed to blood collected immediately after moderate cycling showed only minor changes in gene activity.

This suggests that intense exercise doesn't simply affect the muscles. The substances released into the bloodstream may help communicate the effects of exercise to other parts of the body.

The researchers then compared the proteins affected by exercise with health data from more than 53,000 people in the UK Biobank. They found that many of the proteins influenced by exercise were associated with a lower risk of cardiovascular and metabolic diseases.

One of the most interesting aspects of the research was that the molecular response to intense exercise remained after participants had trained for eight weeks.

"What's exciting here is that just a few minutes of intense exercise can trigger a significant molecular response," says researcher Paul Cohen. "And we still see it after eight weeks of training, which tells us this response isn't simply a product of the body struggling to keep up with unfamiliar stress. It may be that the responses we observed are intrinsic to intense exercise."

The researchers believe the findings may help explain why different types and intensities of exercise produce different effects throughout the body.

"It's well appreciated that different intensities of exercise stimulate distinct body-wide adaptations," noted researcher Luke Olsen. "However, the molecular mechanisms linking these intensity-dependent adaptations have remained largely elusive. Our work suggests that exerkines—proteins and metabolites released into the bloodstream following exercise—are highly sensitive to exercise intensity and may be the key mediators of the health-promoting effects of short bursts of vigorous exercise."

Click here to read more in the journal Cell Reports Medicine.