How Exercise Can Reverse Unhealthy Effects of Inactivity
Many of the
detrimental effects of physical inactivity can be reversed, and in some
cases improved, by a similar period of moderate exercise, Duke
University Medical Center researchers have found. The results are from
a new analysis of data from the first randomized clinical trial to
evaluate the effects of exercise in sedentary overweight men and women.
important, trial participants who exhibited the greatest decline in
physical status during inactivity benefitted the most from exercise
training, according to the researchers.
linking the ability of exercise training to reverse the negative
effects of inactivity can be attributed to the exercise alone, because
the participants did not alter their diets during the trial, the
to lead an inactive lifestyle leads to a gradual decline in many
important markers for cardiovascular health," said Jennifer Robbins, an
exercise physiologist at Duke, who presented the results of the study
during the recent annual meeting of the American College of Sports
Medicine in Denver.
news is that a small amount of physical activity can make a big
difference in reducing the risks for developing such conditions as
heart disease, stroke or diabetes," she said. "Our findings demonstrate
that while the cost of choosing a sedentary lifestyle can be high,
switching to an active way of life can be beneficial at any time."
study stemmed from a recently completed trial known as STRRIDE (Studies
of a Targeted Risk Reduction Intervention through Defined Exercise).
The trial, funded by a $4.3 million grant from the National Heart, Lung
and Blood Institute, investigated the effects of exercise on sedentary
overweight adults at risk for developing heart disease, diabetes, or
trial, in which the intervention ran for six months, randomly assigned
334 participants into three different exercise groups and one control
"At the end
of the trial, we were surprised to see that many markers of
cardiovascular health declined in participants in the control group,
who did not exercise," Robbins said. "Our Duke group decided to see if
these negative effects could be reversed after the participants spent
the same amount of time in an exercise program."
Of the 61
STRRIDE participants randomly assigned to the control group 53 agreed
to the take part in the new study, which ran an additional six months.
The researchers measured 17 biological factors known to increase
cardiovascular risk, including waist size, physical fitness, visceral
fat levels, body mass index, cholesterol levels, insulin sensitivity
and indicators of metabolic syndrome, a precursor of diabetes.
"In the new
analysis, we found that waist size, time to exhaustion, visceral fat
and metabolic syndrome scores deteriorated significantly during the
six-month period of inactivity during the original STRRIDE trial,"
Robbins said. "However, after six months of exercise training in the
study, 13 of the 17 variables had either reverted to original baseline
levels or even improved."
Robbins, only a moderate amount of exercise is needed to counteract the
detrimental effects of inactivity in these individuals. The STRRIDE
trial measured three levels of physical activity: the equivalents of 12
miles of walking per week, 12 miles of jogging per week or 20 miles of
jogging per week. Participants worked out on treadmills, elliptical
trainers or cycle ergometers in a supervised setting.
at the group as a whole, we found it wasn't the participants with the
highest intensity of exercise who accounted for the combined beneficial
effects," Robbins said. "That should be reassuring for people to know
they don't have to do a high-intensity workout to get these benefits of
analysis by the Duke group of the same STRRIDE participants, reported
in 2005, found another unhealthy effect of physical inactivity:
inactive participants gained an average of 2 pounds in six months.
rate, it can be assumed that this group of inactive people would gain
20 pounds in five years," Robbins said. "This means this population of
sedentary people needed to exercise just to maintain their current
weight. However, our earlier studies have shown that people who
exercise can derive many of the cardiovascular risk benefits even in
the absence of weight loss."
trial was led by Duke cardiologist William Kraus, M.D. The Duke team is
currently enrolling patients in STRRIDE II, in which the team will
study the effects of weighttraining, aerobic training, and aerobic and
weight training combined on cardiovascular health.
Robbins in the current study were Cris Slentz, Brian Duscha, Johanna
Johnson and Lori Aiken of Duke, and Joseph Houmard and Jennifer
McCartney of East Carolina University.
Source: Duke University School of Medicine 2006, www.medschool.duke.edu.