Research indicates that about 75 percent of American adults do not exercise and are
overweight. While most people understand that lack of exercise can lead to fat
accumulation, they typically are unaware of the physiological relationships that link
inactivity and weight gain.
In addition to using fewer calories, inactive adults lose between one-half and one
pound of muscle per year. This results in a lower resting metabolism that further
reduces the calories utilized on a daily basis. Due to few calories being expended,
even eating the same quantity of food causes weight gain. Dieting is largely
unsuccessful because it generally results in more muscle loss and an even lower
metabolic rate.
People need to understand that, for the most part, the problem of too much weight is
really a problem of too little exercise. More than that, however, an exercise program
must include strength training to replace muscle and restore resting metabolic rate.
The importance of strength training is illustrated in a study at Tufts University. After
three months of basic strength exercise, the senior subjects added 3 pounds of lean
(muscle) weight, lost 4 pounds of fat weight, raised their resting metabolism by 7
percent and increased their daily calorie intake by 15 percent.
But how much strength training is necessary, and how much time must be allotted for
the overall exercise program? Because the majority of non-exercisers cite lack of time
as their main reason for remaining inactive, a time-efficient training program would
appear to be advantageous.
Most people in the fitness field consider a three-day-per-week, onehour-per-session
exercise program standard for making significant improvements in body composition.
The hour training session is typically divided into about 25 minutes of endurance
exercise, 25 minutes of strength exercise and five minutes each of warm-up and cool-
down activities. But studies show that a program consisting of less time can be
almost as beneficial.
Two vs. Three Days Per Week
In a large research study, 716 previously inactive adults who performed 25 minutes
of endurance exercise, 25 minutes of strength exercise and five minutes each of warm-
up and cool-down activities three days a week for eight weeks experienced a 2.2
percent improvement in body composition. As shown in Table 1, they lost 4.6 pounds
of fat weight and gained 2.5 pounds of lean (muscle) weight.
In the same study, 416 previously sedentary men and women performed the identical
exercise protocol, but trained only two days a week. After eight weeks, they
experienced a 2.0 percent improvement in body composition. As presented in Table 1,
these participants lost 4.0 pounds of fat weight and added 2.2 pounds of lean
(muscle) weight.
On average, the subjects who trained two days per week made 88 percent as
much improvement in their body composition parameters as those who exercised
three days per week. It would therefore appear that training only twice a week is
effective for making significant changes in fat weight and lean weight in previously
inactive adults.
From a practical perspective, it is noteworthy that the two training days in this
study were Tuesdays and Thursdays. In most fitness facilities, Tuesdays and
Thursdays are less crowded than Mondays, Wednesdays, and Fridays, which is
advantageous for attending to beginning participants.
A study of 59 previously sedentary participants was conducted to determine
whether 20-minute exercise periods were sufficient for improving body composition
and physical fitness. Each session included 15 minutes of endurance exercise and
five minutes of strength training. The aerobic activity was either stationary cycling or
stepping, and a typical strength workout was one set of leg presses (quadriceps,
hamstrings, gluteus), one set of bench presses (pectoralis major, deltoids, triceps)
and one set of seated rows (latissimus dorsi, biceps).
After eight weeks of training, the previously inactive men and women improved their
body composition by 2 percent, losing 4 pounds of fat weight and adding 2 pounds of
lean (muscle) weight. They also increased their muscle strength by 23 percent and
improved their cardiovascular endurance by 12 percent. These findings indicate that
relatively brief exercise sessions can be effective for improving both body
composition and physical fitness in formerly sedentary adults. In fact, the changes in
fat weight and lean weight for the 20-minute-per-session exercisers in this study and
the 60-minute-per-session exercisers in the previously presented study were quite
similar.
Understanding Study Results
Do these results imply that training periods longer than 20 minutes are
unnecessary? Not at all. However, they do suggest that unfit individuals may need
less exercise than they think to stimulate desirable physical adaptations. While well-
conditioned participants may benefit from longer training sessions, those with low
fitness levels may have difficulty maintaining productive levels of exercise intensity
for extended periods. Therefore, 20-minute workouts may be worth trying with people
who are unaccustomed to physical activity.
Because lack of time is the most frequently stated reason for not exercising, the
results of these studies are good news for time-pressured men and women. For those
who don’t like to exercise but understand the need to do so, the 20-minute training
session should enhance their workout compliance.
The Surgeon Generals recommendation for 30 minutes of physical activity most days
of the week is certainly a step in the right direction. However, adding some strength
training should be beneficial for replacing muscle and increasing metabolic rate,
which appear to be key factors in attaining and maintaining desirable body
composition. Because a few multiple-muscle strength exercises seem to be sufficient,
a three- to five-station strength circuit may be an attractive facility feature for time-
pressured individuals. Table 3 presents a sample five-station strength training circuit
that should take no more than 10 minutes for completion.
NEWSLETTER of July
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