Why brisk walk is better

Walking, fast or slow, is wonderful exercise.
But now a first-of-its-kind study shows that to
get the most health benefits from walking,
many of us need to pick up the pace. The findings stem from a new analysis of the
National Walkers’ Health Study, a large
database of information maintained at the
Lawrence Berkeley National Laboratory about
thousands of middle-age men and women who
walk regularly for exercise. Recruited beginning in 1998 at walking events and from
lists of subscribers to walking-related
publications, these volunteers filled out a
lengthy survey about their typical walking
distance and pace, as well as their health
history and habits. As most of us would likely guess, walking is the
most popular physical activity in America. But
people who walk for exercise do so at wildly
varying speeds and intensities. Some stroll at a
leisurely 2 miles per hour, which is low-
intensity exercise. Others zip along at twice that pace or better, resulting in a sweatier
workout. Exercise guidelines generally suggest that for
health purposes, people should engage in 30
minutes of moderate-intensity activity most
days of the week. For walkers, a moderately
intense pace would probably be about 15 or 16
minutes per mile. It has generally been assumed that if people
walk more slowly but expend the same total
energy as brisk walkers — meaning that they
spend more time walking — they should gain
the same health benefits. But few large-scale
studies have directly compared the impact of moderate- and light-intensity walking,
especially in terms of longevity. To do so, Paul T. Williams, a statistician at
Lawrence Berkeley National Laboratory,
gathered data about 7,374 male and 31,607
female participants from the walkers’ health
study, who represented almost every speed of
fitness walker, from sluggish to swift. His findings were published online this month in PLoS One. Dr. Williams divided participants into four
numerically equal categories, based on their
normal pace. Those in Category 1, the fleetest,
averaged less than 13.5 minutes per mile,
putting them on the cusp of jogging, while
those in Category 4, the slowest, strolled at a relatively dilatory 17 minutes or more per
mile. The majority of the walkers in this group
in fact required at least 20 minutes to
complete a mile, and many had a pace of 25
minutes or more per mile. (Interestingly, on
average, female walkers were faster than men in all of the categories.) Next, Dr. Williams cross-referenced his data
against that in the essential if somewhat
ghoulish National Death Index to determine
which of the almost 39,000 walkers had died
in the decade or so since they had joined the
survey and from what. It turned out that nearly 2,000 of the walkers
had died. More telling, these deaths
disproportionately were clustered among the
slowest walkers. Those in Category 4 were
about 18 percent more likely to have died from
any cause than those in the other three categories and were particularly vulnerable to
deaths from heart disease and dementia. Unexpectedly, the death rate remained high
among the slowest walkers, even if they met or
exceeded the standard exercise guidelines and
expended as much energy per day as someone
walking briskly for 30 minutes. This effect was
most pronounced among the slowest of the slow walkers, whose pace was 24 minutes per
mile or higher. They were 44 percent more
likely to have died than walkers who moved
faster, even if they met the exercise guidelines. One important inference of these statistics is
that intensity matters, if you are walking for
health. “Our results do suggest that there is a
significant health benefit to pursuing a faster
pace,” Dr. Williams said. Pushing your body,
he said, appears to cause favorable physiological changes that milder exercise
doesn’t replicate. But there are nuances and caveats to that
conclusion. The slowest walkers may have
harbored underlying health conditions that
predisposed them to both a tentative walking
pace and early death. But that possibility
underscores a subtle takeaway of the new study, Dr. Williams said. Measuring your
walking speed, he pointed out, could provide a
barometer of your health status. So check yours, your spouse’s or perhaps your
parents’ pace. The process is easy. Simply find
a 400-meter track and, using a stopwatch,
have everyone walk at his or her normal speed.
If a circuit of the track takes someone 6
minutes or more, that person’s pace is 24 minutes per mile or slower, and he or she
might consider consulting a doctor about
possible health issues, Dr. Williams said. Then, with medical clearance, the slow walkers
probably should try ramping up their speed,
gradually. The most encouraging news embedded in the
new study is that longevity rises with small
improvements in pace. The walkers in
Category 3, for instance, moved at a speed
only a minute or so faster per mile than some
of those in the slowest group, but they enjoyed a significant reduction in their risk of dying
prematurely.