Table 1. Key Terms and Definitions.

Key term	Definition
Physical activity	“Any bodily movement produced by skeletal muscles that result in energy expenditure’’ above resting (basal) levels. Physical activity broadly encompasses exercise, sports, and physical activities done as part of daily living, occupation, leisure, and active transportation” (garber). It is an unstructured and integrated into everyday life and exercise in a prearranged, deliberate, and repetitive manner [6].
Exercise	“Physical activity that is planned, structured, and repetitive and (that) has as a final or intermediate objective the improvement or maintenance of physical fitness” [7].
Physical fitness	“The ability to carry out daily tasks with vigor and alertness, without undue fatigue and with ample energy to enjoy (leisure) pursuits and to meet unforeseen emergencies. Physical fitness is operationalized as “(a set of) measurable health and skill-related attributes” that include cardiorespiratory fitness, muscular strength and endurance, body composition and flexibility, balance, agility, reaction time and power” [7].
Energy expenditure	“The total amount of energy (gross) expended during exercise, including the resting energy expenditure (resting energy expenditure + exercise energy expenditure). Energy expenditure may be articulated in METs, kilocalories or kilojoules” [7].
MET	“An index of energy expenditure. “(A MET is) the ratio of the rate of energy expended during an activity to the rate of energy expended at rest (One) MET is the rate of energy expenditure while sitting at rest...by convention, (1 MET is equal to) an oxygen uptake of 3.5 mL/kg/min” [7].
MET-minutes	“An index of energy expenditure that quantifies the total amount of physical activity performed in a standardized manner across individuals and types of activities. Calculated as the product of the number of METs associated with one or more physical activities and the number of minutes the activities were performed (i.e., METs × minutes). Usually standardized per week or per day. Example: jogging (at about 7 METs) for 30 min on 3 days/week: 7 METs × 30 min × three times per week = 630 MET min/week” [7].
Sedentary behavior	Activity that involves little or no movement or physical activity, having an energy expenditure of about 1 - 1.5 METs. Examples are sitting, watching television, playing video games, and using a computer.
Healthy aging	As obtaining or maintaining “physical, intellectual, emotional, social, vocational and spiritual functioning” (Ng) at the best possible self-perceived level for aging adults [5].
Quality of life	Encompasses “physical and social functioning, emotional well-being, role activities, and individual health perceptions” and is measured by using different questionnaires, and is sometimes referred to as health-related quality of life [8].
Functional performance	The physical, psychological, social, occupational, and spiritual activities that people actually do in the normal course of their lives to meet basic needs, fulfill usual roles, and maintain their health and well-being” [9].

Different key terms with their definitions as expressed within this paper.