For anyone interested in the relationship between exercise and living longer, one of the most pressing questions is how much we really need to stay healthy. Is 30 minutes a day enough? Can we get by with less? Do we have to exercise all in one session, or can we spread it throughout the day? And when we're talking about exercise, does it have to be hard to count?

For years, exercise scientists tried to quantify the ideal "dose" of exercise for most people. They finally reached a broad consensus in 2008 with the Physical Activity Guidelines for Americans, which were updated in 2018 after an extensive review of the available science about movement, sitting and health. In both versions, the guidelines advised anyone who was physically able to accumulate 150 minutes of moderate exercise every week, and half as much if it is intense.

But what's the best way to space out those weekly minutes? And what does "moderate" mean? Here's what some leading researchers in exercise science had to say about weekend warriors, greater longevity and why the healthiest step we can take is the one that gets us off the couch.

"For longevity, 150 minutes a week of moderate to vigorous intensity physical activity clearly is enough," said Dr. I-Min Lee, a professor of epidemiology at the Harvard T.H. Chan School of Public Health. She has extensively studied movement and health and helped draft the current national physical activity guidelines.

For practical purposes, exercise scientists often recommend breaking that 150 minutes into 30-minute sessions of speedy walking or a similar activity five times a week. "It is quite clear from numerous large-scale, well-conducted epidemiological studies that 30 minutes of moderate-intensity activity most days lowers the risk of premature death and many diseases, such as stroke, heart attack, Type 2 diabetes and many types of cancer," said Ulf Ekelund, a professor specializing in physical activity epidemiology at the Norwegian School of Sports Sciences in Oslo, who has led many of those studies.

Moderate exercise means "activities that increase your breathing and heart rate, so the exertion feels like a five or six on a scale between one and 10," he said. In other words, pick up the pace if your inclination is to stroll, but do not feel compelled to sprint.

You also can break up your exercise into even smaller segments. "It doesn't matter whether exercise is done in a long, continuous 30-minute session or is dispersed across the day in shorter sessions," said Emmanuel Stamatakis, an exercise scientist at the University of Sydney in Australia who studies physical activity and health.

Recent studies show that we can accumulate our 150 weekly minutes of moderate exercise in whatever way works best for us, he said. One-or two-minute walks between tasks works. "There is no special magic to a sustained 30-minute session of exercise" for most health benefits.

To concentrate the health benefits of these workout nuggets, he said, keep the intensity relatively high, so you feel somewhat winded. Think of these bite-size workouts as exercise snacks, he added.