Watch the world’s best distance runners, cross-country skiers or rowers on an ordinary training day and much of the time they are going surprisingly slowly. Research on how elite endurance athletes train has found that roughly 80% of their training is done at low intensity, at a steady, comfortable effort.

That figure has a second, less obvious relevance. A separate body of research, following tens of thousands of everyday people for years, suggests that running at modest speeds and in modest amounts is linked to a meaningfully lower risk of death. For people who have avoided running because they assume it has to hurt to count, the evidence points the other way.

How the fastest athletes spend most of their time

Researchers have been measuring how endurance athletes distribute their training intensity for many years. Sports scientist Stephen Seiler is widely credited with pioneering the work. In a 2015 review in Frontiers in Physiology, Stöggl and Sperlich brought together the studies available at the time on the training intensity distribution among well-trained and elite endurance athletes.

Their summary was that elite endurance athletes perform approximately 80% of their training at low intensity, defined physiologically as effort that keeps blood lactate below about 2 millimoles per liter. In practical terms, that is steady, comfortable work. The share varied between studies, from around 70% to as much as 94% of training time, but in the studies reviewed, easy effort usually made up the bulk of it.

The remaining training is usually a mix of moderate and hard sessions. One widely discussed model, called polarized training, keeps most work very easy and a small portion very hard, with relatively little in between. The review noted that this is often described as an 80:20 split.

Elite athletes are a special case, of course, with years of training behind them and goals that are not the same as staying healthy. But their habits undercut the idea that useful running has to be fast.

Fifteen years of data on everyday runners

The best-known study on running and longevity comes from the Cooper Center Longitudinal Study in Dallas. In a 2014 paper in the Journal of the American College of Cardiology, researchers followed 55,137 adults aged 18 to 100, with an average age of 44, for an average of 15 years.

According to the study’s abstract, runners had a 30% lower adjusted risk of dying from any cause during that time and a 45% lower risk of dying from cardiovascular disease, compared with people who did not run. The researchers estimated that this amounted to about three extra years of life expectancy.

What drew the most attention was how little running was needed. People who ran less than 51 minutes a week, covered fewer than 6 miles a week, ran only once or twice a week, or ran at speeds slower than 6 miles an hour still had a lower risk than non-runners. The authors concluded that running “even 5 to 10 min/day and at slow speeds” was associated with these benefits. A pace under 6 miles an hour works out to slower than 10 minutes per mile, a gentle jog for many adults.

Consistency appeared to matter more than speed. Those who kept running over several years of assessment, described as persistent runners, had the largest benefits, with a 29% lower risk of death from any cause and a 50% lower risk of cardiovascular death.

A wider look across 14 studies

One study, however large, can be shaped by the particular people it recruits. In 2019, a team at Victoria University in Melbourne pooled 14 studies involving 232,149 people followed for between 5.5 and 35 years. Their analysis was published in the British Journal of Sports Medicine.

As News-Medical reported, any amount of running was associated with a 27% lower risk of death from all causes, a 30% lower risk of cardiovascular death and a 23% lower risk of death from cancer. The pattern was similar in men and women.

The review found no significant dose-response trend. Running more often, for longer, at a faster pace or in greater total volume did not show a clear additional benefit in the pooled data. Benefits were seen among people who ran once a week or less, for 50 minutes or less, at slow speeds. The authors summed it up plainly: “Any amount of running, even just once a week, is better than no running.”

Is fast running worse for you?

A 2015 Danish study is sometimes cited as evidence that slow running is not just enough but better. Researchers from the Copenhagen City Heart Study, writing in the same cardiology journal, followed 1,098 healthy joggers and 413 healthy non-joggers for 12 years. According to the American College of Cardiology’s release, light and moderate joggers had the lowest death rates, while strenuous joggers had a death rate similar to people who did not exercise.

That conclusion rests on very few cases. As a detailed analysis on the blog Running Writings pointed out, the strenuous group contained 50 people, two of whom died. Numbers that small cannot show whether fast running carries any added risk, and pace was based on how participants described their own running. The larger 14-study review found no significant trend by pace in either direction. The fairer reading is that slow running delivers most of the benefit, not that fast running is dangerous.

What the evidence can and cannot say

All of these health findings come from observational studies. People who choose to run tend to differ from those who do not: in the Copenhagen study, joggers were younger and less likely to smoke or have diabetes. Researchers adjust for such differences where they can, but these studies cannot prove that running itself causes the longer lives. The training research on elite athletes, meanwhile, describes what top competitors do rather than testing what is best for everyone else.

Taken together, though, the two lines of research point in the same direction. The athletes who need endurance most build it largely at an easy pace, and the long-term studies find that ordinary people running slowly and briefly are linked to lower death rates than people who do not run at all. Anyone with a heart condition or other health concern is best advised to check with a doctor before starting. For many others, a slow jog that feels almost too easy may be a sound place to begin, and keeping it up appears to matter more than speed.

Photo: Antoni Shkraba / Pexels