Short on time — say, on a city break with exactly one free morning? A new study suggests a few minutes of all-out effort might do more for your body than an hour and a half of gentle exercise.

The research, published in August in Cell Reports Medicine, was led by cardiologist Paul Cohen at The Rockefeller University in New York. Nineteen healthy young men were split into two groups: one rode a stationary bike at a moderate pace for 90 minutes, the other did six 30-second all-out sprints with rest in between — just three minutes of actual hard work, wrapped up in a 23-minute session.

Then came the striking part. Researchers took blood samples before, immediately after and three hours after each workout, and counted every protein in them. After the short, brutal session, more than 700 proteins had changed in the blood. After the long, easy ride? Just seven — with only 12 more appearing three hours later.

Those proteins aren't random. They act as messages between organs — muscles, liver, fat tissue, immune cells and more — essentially telling distant parts of the body how to respond to exercise. And when the team cross-checked the sprinters' protein changes against health data from roughly 50,000 British adults, 32 of the proteins were linked to lower risks of heart disease, obesity and Type 2 diabetes. For the moderate group, the number was three.

The effects weren't a one-off fluke either. Volunteers who kept up their routines for eight weeks — the sprinters totalling about 72 minutes of hard effort over two months, versus at least 216 hours of moderate riding — showed the same dramatic difference in blood response.

Caveats apply. The subjects were young, healthy and male, so it's unclear whether women, older adults or people with health conditions would see the same results, and nobody knows yet whether three minutes is the magic number. Cohen's own advice is sensible: don't ditch long, mellow workouts, but don't be afraid to push sometimes. An 8-out-of-10 effort — sprinting up stairs, hurrying to a landmark during a walk — appears to count.

For travellers, this is genuinely good news. No gym, no gear, no hour to spare: a few hard hill sprints or stair climbs between sightseeing may deliver outsized health benefits. And for those who prefer a long beach walk or an easy bike tour, that still counts. As Cohen puts it, the goal is simply to be as active as you can — whether that's 90 minutes at a time, or three.

Story via NZ Herald Travel, adapted from Gretchen Reynolds' reporting.