NEW YORK (NYTIMES) - For anyone interested in the relationship between exercise and living longer, one of the most pressing questions is how much do people really need to stay healthy. Is 30 minutes a day enough? Can one get by with less? Does one have to exercise all in a session or can it be spread throughout the day? And when one is talking about exercise, does it have to be hard to count?
For years, exercise scientists have 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 advise anyone who is physically able to accumulate 150 minutes of moderate exercise every week, and half as much if it is intense.
But what is the best way to space out those weekly minutes and what does "moderate" mean? Here is what some of the leading researchers in exercise science have to say about step counts, stairwells, weekend warriors, greater longevity and why the healthiest step people can take is the one that gets them off the couch.
Aim for the 150-minute sweet spot
"For longevity, 150 minutes a week of moderate to vigorous intensity physical activity is enough," says 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.
Professor Ulf Ekelund, who specialises in physical activity epidemiology at the Norwegian School of Sport Sciences in Oslo, says: "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 conditions, such as stroke, heart attack, type two diabetes and many types of cancer."
Moderate exercise, he adds, means "activities that increase your breathing and heart rate, so the exertion feels like a five or six on a scale of one to 10".
In other words, pick up the pace if your inclination is to stroll, but do not feel compelled to sprint.
Consider exercise snacks
You also can break up your exercise into even smaller segments.
Dr Emmanuel Stamatakis, an exercise scientist at the University of Sydney in Australia who studies physical activity and health, says: "It doesn't matter whether exercise is done in a long, continuous 30-minute session or is dispersed across the day in shorter sessions."
Recent studies overwhelmingly show people can accumulate their 150 weekly minutes of moderate exercise in whatever way works best for them, he says.
"Many people may find it easier and more sustainable to squeeze in a few dozen one- or two-minute walks in between work tasks" or other commitments, he adds. "There is no special magic to a sustained 30-minute session of exercise" for most health benefits.
Think of these bite-size workouts as exercise snacks, he says. He adds: "Activities like bursts of very fast walking, stair-climbing and carrying shopping bags provide excellent opportunities for movement snacks."
To concentrate the health benefits of these workout nuggets, he says, keep the intensity relatively high, so you feel somewhat winded.
Count your steps
The exercise recommendations remain the same if you measure your exercise in steps instead of minutes. For most people, says Dr Lee, "150 minutes of exercise a week would translate to about 7,000 to 8,000 steps a day".
In a large-scale new study by Dr Lee and Prof Ekelund of the relationship between steps and longevity, published in March in The Lancet journal, the optimal step count for people younger than 60 was about 8,000 to 10,000 a day. For those age 60 and above, it was about 6,000 to 8,000 a day.
Of course, these recommendations about steps and minutes focus on health and lifespans, not physical performance. "If you want to run a marathon or a 10km race as fast as possible, you need much more exercise," says Prof Ekelund.
The recommended 150 minutes a week may also be too little to stave off weight gain with age. In a 2010 study of almost 35,000 women that was spearheaded by Dr Lee, only those who walked or otherwise exercised moderately for about an hour a day during middle age maintained their weight as they became older.
So, if you have the time and inclination, move more than 30 minutes a day, say Dr Lee and the other scientists. In general, according to her research and other studies, the more active people are, the more their risks of chronic conditions drop and the longer their lives may be.
But any activity is better than none. "Every single minute counts," says Prof Ekelund. "Walking up the stairs has health benefits, even if it lasts for only one or two minutes, if you repeat it regularly."