Physical Activity and Exercise

Physical activity is the umbrella term used to describe any bodily movement produced by contracting skeletal muscle that increases energy expenditure above a basal level. Exercise is physical activity that is planned, structured, and done repetitively to improve health or fitness.

The three main types of exercise are as follows:

• Aerobic (endurance) exercise
• Muscle-strengthening exercise (resistance or weight training)
• Bone-strengthening exercise (weight-bearing exercise)

In aerobic (or endurance) exercise, you move large muscles in your body rhythmically for a sustained period of time. This causes your heart to beat faster than usual. Examples include: brisk walking, running, bicycling, jumping rope and swimming.

Three components of aerobic exercise include intensity, frequency, and duration.

When you do muscle-strengthening exercise, your muscles work or are held against a force or weight. Examples include resistance training and lifting weights.

Elastic resistance bands can be used to perform resistance exercise, as can your own body weight (to do push-ups, lunges, or squats), free weights (dumbbells or barbells), and some exercise equipment (such as a leg press machine).

Three components of muscle-strengthening exercise include intensity, frequency, and repetitions.

Bone-strengthening exercise (also known as weight-bearing or weight-loading activity) applies force to bones to help them grow and strengthen; for example, when you walk, a force is created by impact with the ground. Examples of exercises that strengthen bones (and are also considered aerobic and muscle-strengthening) include jumping jacks, running, brisk walking, and weight –lifting.

Health Benefits and Risks

Incorporating regular exercise into your life can provide you with countless health and other benefits. Research shows that physical activity can benefit adults and children by

• Improving cardiorespiratory fitness
• Improving muscular fitness
• Improving bone health
• Improving cardiovascular and metabolic health biomarkers

In adults and older adults, there’s strong evidence that regular physical activity

• Reduces the risk of coronary heart disease, stroke, high blood pressure, type 2 diabetes, metabolic syndrome, and some cancers (including colon and breast) as well as early death from heart disease, some cancers, and other conditions.
• Reduces the risk of unhealthy blood lipid levels
• Improves cardiorespiratory and muscular fitness
• Helps prevent falls that can potentially lead to fracture
• Reduces risk of depression
• Improves cognition (including thinking, learning, and judgment skills) in older people

Physical activity might also reduce symptoms of depression, improve functional ability, increase bone density, reduce hip fracture risk, improve the quality of sleep, and reduce the risk of lung and endometrial cancers.

Role in Weight Management

How physically active you are in general plays a key role in determining how much you weigh and how well you are able to maintain your weight over the long-term. Although engaging in aerobic or endurance-type exercise is most effective in helping you maintain your body weight, doing weights and other muscle-strengthening exercise also helps. Regular exercise can help both children and adults keep their body fat levels down (the more muscle mass you have, the more calories you burn or use up and the less body fat you have).

Being physically active, especially when you also reduce your total daily calorie intake, can create an energy deficit that leads to weight loss. Physical activity might also help reduce fat in the abdominal area (too much abdominal or visceral fat can increase the risk for heart disease and other conditions). Studies also show that for those who have lost weight, being physically active is the best way to keep weight off long-term.

Most physical activities pose little risk for most people, but doing too much physical activity and exercise or suddenly becoming more active than usual can increase your risk for musculoskeletal injuries. Some sports, including contact sports like soccer or football, can also be associated with a higher injury risk.

Weekly Recommendations

To complement the Dietary Guidelines for Americans, in 2008 the U.S. Department of Health and Human Services (HHS) issued Physical Activity Guidelines for Americans ages 6 and above. These science-based guidelines are the first to be unveiled by the U.S. government in an effort to help Americans understand the importance of physical activity and exercise and incorporate more of it into their daily lives.

For adults and older adults without health or medical conditions that limit their mobility, both aerobic and muscle-strengthening exercise are recommended. The weekly recommendations are as follows:

• Aerobic exercise – 2 ½ hours (150 minutes) at moderate intensity + 1 ¼ hours (75 minutes) at vigorous intensity or 1 ¼ hours (75 minutes) each of moderate and vigorous-intensity exercise
• Muscle-strengthening exercise (that works all the major muscle groups including legs, hips, back, abdomen, chest, shoulders, and arms) – 2 or more days per week, but never the same muscles on back-to-back days

Pregnant women who already engage in vigorous activity such as running can continue with such activity but should work with their health-care provider to adjust their activity level over time. After the first trimester, pregnant women should avoid exercises in which they need to lie on their backs as well as activities that can increase the risk of falls or abdominal trauma including downhill skiing, horseback riding, soccer, and basketball. They should also avoid scuba diving because it can cause dangerous gas bubbles in the baby’s circulatory system.

Here’s what recommended for children aged 6 and above:

• At least 1 hour (60 minutes) of physical activity, mostly from aerobic exercise; muscle- and bone-strengthening activities should also be included as part of the 60 minute recommendation.

Intensity is the amount of effort needed to perform an activity or exercise.
Frequency s how often or the number of times an activity or exercise is performed.
Duration is how long a period of time (in minutes or hours) during which an activity or exercise is performed.
Repetition refers to an exercise (for example, lifting weights or performing some other muscle-strengthening activity or exercise) that is repeated and often counted.
Cardiorespiratory fitness (also known as endurance) is a health-related component of physical fitness; it is the ability of the circulatory and respiratory systems to supply oxygen during sustained physical activity.
Functional ability is an individual’s ability to perform tasks or behaviors that enable her to carry out everyday activities (for example, climbing stairs, going grocery shopping, or preparing meals at home).
Moderate-intensity physical activity is activity performed at 3 – 5.9 times the intensity of rest.
Vigorous – intensity physical activity is activity performed at 6 or more times the intensity of rest.

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