Physical Activity: Definition, Intensity, Types and Health Benefits

Physical Activity

Concept: The generally accepted definition of physical activity (physical activity) is from the Annual Review of Public Health 2005: "Physical activity is any bodily movement produced by skeletal muscle contraction that substantially increases energy expenditure." This definition is used by the public health field and may require certain precisions regarding physical exercise in specific situations.

a) Maintaining positions in immobility, or positions that do not increase energy expenditure such as yoga postures (asanas) or isometric contraction, are not considered physical activity under this definition, since they involve no displacement.

b) Exercises that do not produce skeletal muscle contraction but only stretching, such as stretches using gravity, are considered physical activities if they are sports or fitness activities.

c) Movements without muscle contraction, such as passive exercise, are not considered physical activity.

d) Electrostimulation that produces skeletal muscle contraction and some increase in energy expenditure can, on some occasions, be considered physical activity.

Description

Physical activity may be described in terms of:

a) Duration: The time the activity is active, generally expressed in minutes.

b) Intensity: Intensity can be measured by:

• b1. Calories consumed per minute: Moderate activity is between 3.6 and 7.2 kcal per minute for a person weighing 70 kg. Vigorous activity is above 7.2 kcal per minute.
• b2. METs (metabolic equivalent of task): The MET is a unit related to oxygen consumption. It estimates the amount of oxygen the body uses during physical activity. 1 MET = the oxygen used by the body while sitting quietly, such as reading or watching television. Activities from 3 to 6 METs are considered moderate-intensity physical activity. Activities above 6 METs are considered vigorous-intensity physical activity. 1 MET = 1.2 kcal.
• b3. Heart rate: Moderate intensity is 50-70% of maximum heart rate per minute; vigorous intensity is 70-80% of maximum heart rate per minute. Maximum heart rate = 220 minus age.
• b4. Observable physiological manifestations: Physical activity that causes sweating and slightly faster breathing, with deeper breaths than usual.
• b5. Borg scale: A holistic scale of perceived exertion.

c) Type: The Annual Review of Public Health preferentially classifies physical activity into the following categories:

1. Recreational activity: dance, fitness conditioning.
2. Household activity: chores, gardening.
3. Garden and hobby work activity.
4. Occupational activity.
5. Non-motorized transport: cycling, climbing stairs.

d) Purpose: Recreation, health, training, gaining fitness, staying fit, losing weight, etc.