-------- Original Message --------

NOTE: To view the article with Web enhancements, go to:
http://www.medscape.com/viewarticle/556638

Even Small Amounts of Exercise Are Beneficial CME/CE

News Author: Sue Hughes
CME Author: Charles Vega, MD


May 17, 2007 — Even small amounts of physical activity — approximately 75
minutes per week — can improve cardiorespiratory fitness levels of sedentary
overweight individuals, a study shows.

While this level of exercise is lower than that currently recommended to produce
weight loss, the current findings may be used to encourage those people who do
not exercise at present to start doing some form of physical activity, the
authors advise.

The study, published in the May 16 issue of JAMA, was conducted by a team led by
Timothy S. Church, MD, MPH, PhD, from the Louisiana State University System in
Baton Rouge.

The authors point out that improvements in fitness are associated with a
reduction in the risk for cardiovascular disease and death, and that, as
physical activity is the main determinant of fitness in adults, continuing to
refine efficient, safe, and acceptable exercise regimens is of substantial
public health importance. Whereas the National Institutes of Health (NIH)
Consensus Development Panel recommends at least 30 minutes of moderate-intensity
physical activity on most days of the week, the authors note that recent reports
suggest that 60 minutes of exercise each day may be necessary to prevent weight
gain. But they add that the effect of much lower amounts of exercise has not
been well studied.

The team therefore conducted a trial in which 464 sedentary postmenopausal women
who were overweight or obese and had raised blood pressure were randomized to 3
different durations of moderate exercise (cycling or walking) or to a
nonexercise control group for 6 months. The 3 exercise levels were designed to
achieve energy expenditure of 4 kcal/kg (400 calories), 8 kcal/kg (800
calories), or 12 kcal/kg (1200 calories) per week, which corresponded to 50%,
100%, and 150% of NIH-recommended exercise levels. Aerobic fitness was assessed
on a cycle ergometer and quantified as peak absolute oxygen consumption. Results
showed a graded increase in fitness levels with increased exercise levels.
Table. Relationship Between Exercise Time and Fitness Level
Parameters Weekly Energy Expenditure, kcal/kg
4 8 12
Exercise time per week, minutes 72.2 135.8 191.7
Change in peak absolute oxygen consumption vs control, % 4.2 6.0 8.2

Source: JAMA. 2007;297:2081-2091.

Church and colleagues report that these improvements in fitness occurred at a
modest training intensity and during a time of life when fitness is decreasing
at 1% to 2% per year. They also point out that the adherence rate was high and
dropout rate was low, suggesting that the exercise regimens followed in this
study were realistic and achievable. In addition, they found that the physical
activity–fitness dose response relation to be similar across age, race, weight,
baseline fitness, and hormone therapy subgroups.

Although the changes in fitness shown in this study were not accompanied by a
reduction in blood pressure, weight, or most other cardiovascular risk factors,
those who exercised did show a decrease in waist circumference, which the
authors say is important given the increased risk for insulin resistance,
diabetes, metabolic syndrome, and mortality associated with excess abdominal
fat.

"Perhaps the most striking finding of our study is that even activity at the
4-kcal/kg per week level (approximately 72 min/wk) was associated with a
significant improvement in fitness compared with women in the nonexercise
control group," the authors write.

They note that nearly everyone understands that there are health benefits
associated with physical activity, yet still about 20% of US adults do not
engage in any physical activity at all. "Data presented in our study show that
even 72 minutes of moderate-intensity physical activity per week accumulated
over about 3 days has a significant effect on fitness in previously sedentary
postmenopausal women. This information can be used to support future
recommendations and should be encouraging to sedentary adults who find it
difficult to find the time for 150 minutes of activity per week, let alone 60
minutes per day," they add.
How Much Exercise Do We Need?

In an accompanying editorial, I-Min Lee, MBBS, ScD, from Brigham and Women's
Hospital in Boston, Massachusetts, explains that guidelines on how much exercise
should be done have varied, with recommendations from the 1970s and 1980s
prescribing vigorous exercise (eg, running) for 20 minutes continuously, 3 days
per week; those from the 1990s suggesting at least 30 minutes per day of
accumulated moderate-intensity activity (eg, brisk walking) most days of the
week; and most recent reports advocating at least 60 minutes per day of moderate
activity. "Predictably, many patients and clinicians are confused about what
dose of physical activity is needed," she writes, adding that the current study
provides some clarification on the dose-response issue.

But she adds that overweight individuals should not be lulled into believing
that 72 minutes per week of physical activity will ameliorate their weight
concerns and that, given the typical US diet, guidelines suggesting 60 minutes
or more of daily physical activity are more appropriate if weight control is the
primary goal.

The editorialist also points out that many questions remain unanswered. These
include whether vigorous activities, such as running, can improve the
cardiovascular risk factors that the moderate activities in the current study
did not, whether a different pattern of moderate exercise would show the same
fitness gain, and what the highest advisable level of exercise is.
Even a Little Is Good; More May Be Better

But Dr. Lee concludes, "Although current knowledge regarding the dose-response
relation between physical activity and health remains incomplete, the study by
Church et al does provide important information on the dose of physical activity
to improve physical fitness, a strong predictor of chronic disease and premature
mortality. This may be succinctly summarized for patients and clinicians as
'Even a little is good; more may be better!'"

JAMA. 2007;297:2053, 2081-2091.

The complete contents of Heartwire, a professional news service of WebMD, can be
found at www.theheart.org, a Web site for cardiovascular healthcare
professionals.
Learning Objectives for This Educational Activity
Upon completion of this activity, participants will be able to:

* Identify current recommendations for physical activity among adults.
* Describe the effect of increasing levels of physical activity on
postmenopausal women.

Clinical Context

The NIH Consensus Development Panel recommends that adults perform at least 30
minutes of moderate-intensity physical activity on most, if not all, days of the
week. Unfortunately, many adults in the United States do not even approach
achieving this standard. Nearly one third of postmenopausal women in the United
States report no physical activity at all and the overall level of inactivity
increases with age.

The NIH recommendation is based on available data on exercise in adults, but the
question of the ideal level of physical activity to prevent chronic disease is
debatable. The effect of increasing levels of exercise on improving physical
fitness is also unclear, and the authors of the current study examine a cohort
of postmenopausal women to address this question.
Study Highlights

* Eligible patients were postmenopausal women between the ages of 45 and 75
years who had a body mass index between 25 and 43 kg/m2 and a systolic blood
pressure between 120 and 159.9 mm Hg. All women included in the trial were
sedentary at baseline. Women with a history of stroke or myocardial infarction
were excluded from study participation.
* Women were randomized into 1 of 4 groups: no exercise (control) or
exercise groups designed to expend 4, 8, or 12 kcal/kg per week. These exercise
levels were designed to represent 50%, 100%, and 150% of current NIH-recommended
exercise levels. Exercise was to be completed during 3 or 4 sessions each week
for 6 months and consisted of walking or cycling. Exercise was conducted at 50%
of estimated peak levels for each individual.
* The primary outcome was the difference in peak absolute oxygen
consumption, a measure of physical fitness, during cycle ergometry at baseline
and 6 months. Other fitness outcomes included peak relative oxygen consumption,
peak power output, and maximal metabolic equivalent tasks achieved during
exercise testing.
* To try to standardize the level of exercise in each group, subjects wore
pedometers to record daily steps. Adherence to the study protocol was encouraged
with financial rewards. Subjects were also followed up for anthropometric data,
serum lipid values, serum glucose levels, and blood pressure.
* 464 women underwent randomization, and 92% of the study cohort completed
follow-up testing at 6 months. The mean age of subjects was 57.3 years, and the
mean body mass index was 31.8 kg/m2. Mean baseline systolic blood pressure was
139.8 mm Hg, although baseline mean lipid and glucose levels were at expected
levels for subjects' age. Baseline levels of physical fitness were very low.
* Weekly mean exercise durations in the 4-, 8-, and 12-kcal/kg per week
exercise groups were 72.2, 135.8, and 191.7 minutes, respectively. The mean
numbers of weekly exercise sessions per group were 2.6, 2.8, and 3.1,
respectively.
* The numbers of daily steps outside of the exercise sessions were roughly
similar for all treatment groups.
* There was a significant trend of improving fitness with greater amounts
of exercise. The peak absolute oxygen consumption increased by 4.2%, 6%, and
8.2% vs the control groups in the 4-, 8-, and 12-kcal/kg per week exercise
groups, respectively. Outcomes for peak relative oxygen concentration and
metabolic equivalent tasks achieved during exercise were similar, with
increasing duration of exercise associated with improved fitness.
* Weight and body fat percentage remained stable in all treatment groups,
although waist circumference was smaller in the exercise groups vs controls.
* Blood pressure and serum lipid values were not improved with exercise vs
control treatment. There was a trend toward reduced fasting glucose levels with
greater levels of exercise.
* Subgroup analysis based on age, body mass index, weight, and baseline
fitness did not significantly alter the study's main result.

Pearls for Practice

* The NIH Consensus Development Panel recommends that adults perform at
least 30 minutes of moderate-intensity physical activity on most, if not all,
days of the week.
* The current study suggests that progressively increasing levels of
exercise can result in a graded improvement in physical fitness among sedentary
postmenopausal women who are obese or overweight. However, exercise did not
improve weight, body fat percentage, or blood pressure.