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USE OF CALORIES
Physical activity can increase the basal metabolic rate, which is the
number of calories used by the body when it is at rest. The increase in
basal metabolic rate is approximately 10%, and possibly lasts for as long
as 48 hours after the completion of the activity.
Physical activity helps in the utilization of calories. The number of
calories used is dependent on the type and intensity of the activity,
and on the body weight of the person performing the physical activity.
Physical activity assists in reducing the appetite. For the purpose of
weight loss, physical activity can reduce body fat and is more beneficial
in combination with reduced intake of calories.
Physical activity also helps in the maintenance and control of weight.
The following are some variables when physical activity and calorie expenditure
is considered:
Time: The amount of time spent on physical activity affects the
amount of calories that will be expended. For example, walking for 45
minutes will burn more calories than walking for 20 minutes.
Weight: The body weight of a person doing the physical activity
also impacts the amount of calories used. For example, a 250-pound person
will expend more energy walking for 30 minutes than a 185-pound person.
Pace: The rate at which a person performs the physical activity
will also affect the amount of calories used. For example, walking 3 miles
per hour will burn more calories than walking 1.5 miles per hour.
BASAL METABOLIC RATE
Basal metabolic rate accounts for most of a person's calorie use. A person's
basal metabolic rate is based on body functions such as respiration, digestion,
heartbeat, and brain function. The age, sex, body weight, and the type
of physical activity impact the basal metabolic rate. Basal metabolic
rate increases with the amount of muscle tissue a person has, and it reduces
with age.
Along with use of
calories, the basal metabolic rate is increased during physical activity
and also after the physical activity. The basal metabolic rate can remain
increased 6 to 24 hours after 30 minutes of moderate type of physical
activity. For many people the basal metabolic rate can be increased 10%
for approximately 48 hours after the activity. For example, after the
physical activity, even when a person is sedentary and watching television,
their body is using more calories than usual.
PHYSICAL ACTIVITY
AND APPETITE
Physical activity at a moderate rate does not increase the appetite. In
some situations, the appetite will actually decrease. Research indicates
that the decrease in appetite after physical activity is greater in individuals
who are obese than in individuals who are at their desirable body weight.
PHYSICAL ACTIVITY
AND LOSS OF BODY FAT
A person loses 25% of his or her lean body mass and 75% of his or her
fat when losing weight through calorie reduction alone. In combination
with physical activity, the loss in body fat is 98%. Weight loss that
is achieved with a combination of calorie restriction and physical activity
is more effective. For maintenance of desirable body weight, a maintenance
level of calories along with physical activity is recommended to preserve
lean body mass and muscle tone.
PRESCRIPTION FOR
PHYSICAL ACTIVITY
The recommendations provided by the American College of Sports Medicine
for weight loss and maintenance are as follows:
Pursue physical activity at least three times a week. Increasing it to
four to five times a week is even more beneficial. Spread out the physical
activity through the week rather than doing it on three or four consecutive
days to decrease the risk of related injuries.
Physical activity should be done at 60 to 90% of the maximum heart rate.
To calculate the maximum heart rate, use the following formula is used:
à Subtract
age from 220 (beats per minute) to get the maximum heart rate. Then multiply
this figure by the intensity level.
For example, a 50-year
old woman exercising at 60% maximum would use the following calculation:
à 220 - 50
= 170 (maximum heart rate)
à 170 X 60% = 102 which is the target heart rate regardless of
the type of physical activity he/she selects to do.
Physical activity
at 60 to 70% of the maximum heart rate can be continued at a safe rate
for a long period of time. If an exercise is too strenuous, conversation
cannot be carried on during the physical activity (the person is out of
breath).
According to the American
College of Sports Medicine, physical activity of less than 2 times a week
at less than 60% of the maximum heart rate, and for less than 10 minutes
per day, does not assist in developing and maintaining fitness. If physical
activity is discontinued, the fitness benefits are completely lost. Within
2 to 3 weeks the level of fitness is reduced, and within 3 to 8 months
it is completely lost, and the person has to restart again.
Twenty minutes of
continuous aerobic activity 3 days per week is recommended for weight
loss. Examples of physical activity that are considered aerobic are: walking,
running, jogging, hiking, swimming, bike riding, rowing, cross country
skiing, and jumping rope.
BENEFITS
Physical activity contributes to health by reducing the heart rate, decreasing
the risk for cardiovascular disease, and reducing the amount of bone loss
that is associated with age and osteoporosis. Physical activity also helps
the body use calories more efficiently, thereby helping in weight loss
and maintenance. It can increase basal metabolic rate, reduces appetite,
and helps in the reduction of body fat.
SIDE EFFECTS
Physical activity should be done at a rate that is appropriate for the
person. An evaluation by an exercise physiologist is helpful to avoid
injuries that can occur if physical activity is initiated without much
consideration given to the type, duration of physical activity, and the
physical condition of the person.
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