Glossary of Terms
Glossary of Terms Related to Physical Activity, Sedentary Behavior, and Physical Function

Physical Activity - Bodily movement that is produced by the contraction of skeletal muscle and that substantially increases energy expenditure

Exercise - Planned, structured, and repetitive bodily movement done to improve or maintain one or more components of physical fitness. Exercise is a specific sub-category of physical activity

Physical Fitness - A set of attributes (e.g., muscle strength and endurance, cardiorespiratory fitness, flexibility, etc., ) that people have or achieve that relate to the ability to perform physical activity

Sedentary Behavior - refers to any waking activity characterized by an energy expenditure ≤ 1.% METS and a sitting or reclining posture

Energy - A product of substrate metabolism that facilitates biological work

Energy Expenditure - The total exchange of energy required to perform a specific type of biological work. Often used to express the volume of physical activity performed during a defined time frame. Energy Expenditure can be expressed as a gross or net term.

Gross Energy Expenditure - The total amount of energy expended for a specific activity including the resting energy expenditure. Gross energy expenditure is typically used for between person comparisons.

Net Energy Expenditure - The energy expenditure associated exclusively with the activity itself. Computed as gross energy expenditure minus the individual’s resting energy expenditure. This term is used to compare the energy costs of specific activities.

Calorimetry - Methods used to calculate the rate and quantity of energy expenditure when the body is at rest and during physical activity

Calorie - A unit of energy that reflects the amount of heat required to raise the temperature of 1 gram of water by 1 °C

Kilocalories (kcal) - 1,000 calories, 4.184 kilojoules. Used to express the energy expended during physical activity

Kilojoules (kJ) - The unit of energy in the International System of Units. 1,000 Joules, 0.238 kcal

Metabolic Equivalent (MET) - A unit used to estimate the metabolic cost (oxygen consumption) of physical activity. One MET equals the resting metabolic rate of approximately 3.5 ml O2≅kg-1≅min-1, or, 1 kcal≅kg-1≅hr-1

MET-minutes - The rate of energy expenditure expressed as METs per minute, which is calculated by multiplying the minutes a specific activity is performed by the corresponding energy cost METs) of the activity

MET-hours - The rate of energy expenditure expressed as METs per hour, which is calculated by multiplying the hours a specific activity is performed by the corresponding energy cost (METs) of the activity

Mode - The dimension of physical activity that identifies the specific type of activity (e.g., walking, bicycling, jumping, weight lifting, bowling, etc) being performed.

Frequency - The dimension of physical activity referring to how often an activity is performed

Duration - The dimension of physical activity referring to the amount of time (e.g., min, hr, days) an activity is performed

Intensity - The dimension of physical activity referring to the level of effort or physiological demand required to perform the activity. Intensity can be expressed as an absolute or relative term

Absolute Intensity - A standard or actual rate of energy expenditure (e.g., L O2 uptake•min-1, METs, Kcal•min-1) assumed for a specific activity

Relative Intensity - The rate of energy expenditure for a specific activity expressed as a percentage of the individual’s maximal capacity to do physical work (e.g., % maximal oxygen uptake, % heart rate reserve).

Hours/Minutes - Typical units of time used in quantifying the rate of energy expenditure or the period of physical activity measurement (e.g., kcal per minute or kcal≅min-1)

Unitless Indices - A unitless number that is computed as an ordinal measure of physical activity (e.g., 10-50, low to high activity level)

Dose-Response - A relationship where increasing levels or “doses” of physical activity result in corresponding changes in the expected levels of a defined physical performance or health parameter

Physical Function - Physical Function is defined as one's ability to carry out various activities, ranging from self-care (activities of daily living) to more challenging and vigorous activities that require increasing degrees of mobility, strength or endurance.

Health Related Quality of Life (HRQoL) - A multi-dimensional concept that includes domains related to physical, mental, emotional, and social functioning.

Activities of Daily Living (ADL) – The performance of basic personal tasks that are necessary for self-care of an individual. These tasks include bathing, dressing, toileting, transfer, continence, and feeding.

Instrumental Activities of Daily Living (IADL) - Instrumental Activities of Daily Living are similar to ADLs but are not necessary for fundamental functioning. IADLs let an individual live independently in a community. These tasks include, but are not limited to: managing medication, maintaining a home, shopping, using transportation.

Balance - The ability to maintain an upright position in space.

Mobility - The ability to move in one’s environment with ease and without restriction.

Muscular Endurance - The ability of a muscle or muscle group to repeat a movement many times or to hold a particular position for an extended period of time.

Flexibility - The degree to which an individual muscle will lengthen.

Gait - The manner or style of walking.

Adapted from: Caspersen, Powell, and Christenson, 1985; Corbin, Pangrazi & Franks, 2000; Howley, 2001, Stewart & Kamberg, 1992; Haley, Coster & Binda-Sundberg, 1994; Haley, McHorney & Ware, 1994; Wilson & Cleary, 1995.