Two recent articles leave this reader confused about the answer to a vital question.
Just three days ago, National Public Radio ran a piece entitled Take A Hike To Do Your Heart And Spirit Good.
This was a study of postmenopausal women who, for six months, came into the lab to walk a treadmill while researchers watched. The results indicated that “ metabolism of blood sugar” improved in even the control group that walked moderately for just 73 minutes a week. There was no apparent improvement in results in two other control groups, one walking for 136 minutes, and the other for 190 minutes per week. The premise was that even walking an average of 10 minutes per day produced 95% of the benefits of jogging, without the drawbacks.
But how does that jive with the New York Times article from May 1, 2015, entitled The Right Dose of Exercise for a Longer Life ?
Gretchen Reynold’s NYTimes piece references two very large studies that were detailed in the April 2015 issue of JAMA Internal Medicine.
The first study followed 14 years of death records of 661,000 middle aged adults. It tracked exercise habits, and grouped the findings from those who did no exercise whatsoever to those who exercised a massive amount (25 hours a week). For reference, US National health guidelines recommend that we engage in 150 minutes per week of moderate exercise.
The results indicated that those who did no exercise at all had the greatest risk of death. The next group did exercise but did not meet the 150 minute per week guideline, and reduced their death risk by 20%. The group that met the 150 minute US Guidelines went on to reduce their risk by 31%. The “ sweet spot” though, was a group that exercised 450 minutes per week, or just over an hour a day, reducing their death risk by 39%. After that, the investment in exercise duration tanked, with the group exercising 25 hours a week doing no better ( 31% reduction) than the 150 minute per week group.
The second cohort, an Australian study, followed 210,000 individuals, and also tracked death statistics. Three groups were aggregated: walkers, runners, and those who exercised more intensively.
Moderate walking produced a “ substantial reduction” in death risk.
Reynolds then writes that, “But if someone engaged in even occasional vigorous exercise, he or she gained a small but not unimportant additional reduction in mortality. Those who spent up to 30 percent of their weekly exercise time in vigorous activities were 9 percent less likely to die prematurely than people who exercised for the same amount of time but always moderately, while those who spent more than 30 percent of their exercise time in strenuous activities gained an extra 13 percent reduction in early mortality, compared with people who never broke much of a sweat. The researchers did not note any increase in mortality, among those few people completing the largest amounts of intense exercise.”
Klaus Gebel, a senior research fellow at James Cook University in Cairns, Australia, who led the second study says, “Anyone who is physically capable of activity should try to reach at least 150 minutes of physical activity per week and have around 20 to 30 minutes of that be vigorous activity.”
My own personal research is in agreement with the “ sweet spot” in the JAMA study. For me, 150 minutes a week maintains some measure of health, but did not significantly improve my fitness. For that, I need more activity.
Since January 2015, I’ve been riding my mountain bike in the woods three times a week, and walking the other days. If I take the occasional day off, I make up for it by putting in a few more hours some other day, maintaining my 1 hour per week average.
My weight is now down 15 pounds, and my cholesterol profile and blood pressure have moved into the normal range. I’ve gained these measurable results from exercising moderately to intensively for 420 minutes a week, or a average an hour a day.
So… just enough, not enough or just right ?
What’s working for you?