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Moderation Appears Key to Sustaining an Exercise Program

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Duke Health News 919-660-1306

SAN FRANCISCO -- While an intensive exercise regimen has
been shown to yield the most health benefits in overweight
sedentary adults, Duke University Medical Center researchers
have found that when given their choice, these adults
apparently tend to gravitate toward a moderate exercise program
approximately equivalent to 11 miles of brisk walking or
jogging each week.

The results of their analysis lead the researchers to
conclude that lower amounts of high intensity exercise might
lead to increased adherence to an exercise program.

"It is important to remember that the more exercise you do
the more benefits you gain, but when focusing on what people
will implement into their daily lives outside of a supervised
setting, it appears that these adults prefer to do fewer
minutes at a higher intensity versus more minutes at a lower
intensity regardless what they did in the supervised program,"
said Lori Aiken, who presented the results of the Duke study
today (May 29, 2003) during the 50th annual scientific sessions
of the American College of Sports Medicine.

The researchers also found that lack of time was the most
common reason given for not continuing to exercise after
completing their initial program, and that the most preferred
form of exercise was walking.

For their analysis, the Duke team randomized 87 "couch
potatoes" to one of three nine-month supervised exercise
programs differing in amount and intensity: low, moderate or
high. The amount of exercise was measured in minutes of
exercise per week, while intensity was measured by a
calculation known as V02max (subscript 2), which is the maximum
amount of oxygen that can be delivered by circulating blood to
tissues in a given period of time.

Those in the low group exercised on average 187 minutes per
week at an intensity of 40 to 55 percent VO2max, or the
equivalent of 11 miles per week of walking. The moderate group
exercised 123 minutes per week at 65 to 80 percent VO2max, or
the equivalent of brisk walking/jogging 11 miles per week. The
high group exercised 180 minutes per week at 65 to 80 percent
VO2max, or the equivalent of brisk walking/jogging 18 miles per
week.

Participants were given individualized exercise
"prescriptions" which took into account their particular health
and fitness status. During the supervised portion of the study,
they used cycle ergometers, treadmills or elliptical trainers
to reach their specified training range. After the completion
of the supervised program, the researchers then contacted the
participants at home to see to what extent they were continuing
their exercise programs.

"Although the participants in the high exercise group gained
the most health benefits during the supervised part of the
program, when they returned home they significantly cut back on
the minutes per week and intensity of their exercise," Aiken
said. ""Furthermore, the participants in the low exercise group
decreased the number of minutes per week but significantly
increased the intensity of their exercise during the six-month
follow-up period. This suggests to us that most people tend to
move toward an exercise regimen more closely resembling the
moderate group.

"The number of participants who continued to exercise after
the supervised portion of the study remained fairly
encouraging, with 69 percent of the low group, 70 percent of
the moderate group and 61 percent of the high group still
exercising," Aiken continued. "Most exercise studies run for
three months. Our program was much longer than most, which may
have been a realistic amount of time for exercise to become
habitual."

In terms of weekly amount of time spent exercising each
week, only the moderate group chose to increase, from 123
minutes to 131 minutes. This group was evenly split between
those who increased, decreased or did not change their level of
intensity.

The high exercise group chose to change their exercise
prescription the most by significantly dropping, from 180 to
135 minutes per week, Aiken said. In terms of intensity, 53
percent cut their intensity, while only 12 percent increased.
The remaining 35 percent did not change.

Although participants in the low exercise group chose to
exercise fewer minutes per week, dropping from 187 to 159
minutes, 68 percent increased the intensity of their exercise.
Only 14 percent decreased intensity and 18 percent remained the
same.

In addition to measuring the exercise habits of the study
participants, the researchers also sought to discover why the
exercisers stopped their exercise programs. Sixty-nine percent
of participants cited time constraints as the main issue. Other
reasons reported were lack of motivation (45 percent), family
obligations and lack of exercise facilities (both 17 percent),
illness or injury (14 percent), and lack of support or travel
(3 percent).

During the supervised portion of the study, participants
exercised at the Duke Center for Living. As part of their
survey, the researchers also sought to find out what mode of
exercise the participants were likely to follow at home.

"By far, walking was the exercise of choice, with 84 percent
of participants reporting this mode of exercise," Aiken said.
"For most people, walking is the most comfortable and
convenient form of exercise."

Other forms of exercise included elliptical trainers and
other machines (22 percent), running (17 percent), bicycling
(16 percent) or swimming (9 percent). Additionally, 16 percent
reported that they stretched before exercise, while 47 percent
said they included some form of weight training.

The Duke team was led by cardiologist William Kraus, M.D.,
who received a $4.3 million grant from the National Heart, Lung
and Blood Institute in 1998 to investigate the effects of
exercise on sedentary overweight adults at risk for developing
heart disease and/or diabetes. The results of that five-year
trial, dubbed STRRIDE (Studies of Targeted Risk Reduction
Interventions through Defined Exercise), are now being
published and presented.

Joining Aiken were Duke colleagues Johanna Johnson, Brian
Duscha, Cris Slentz and Kraus.

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