Defined Terms

Aerobic activities use the larger muscle groups over an extended time period where the energy is supplied by the oxygen utilizing process. Sample activities include walking, jogging, swimming, and cycling.

Aerobic capacity is the highest amount of oxygen consumed during maximal exercise in activities that use the large muscle groups in the legs or arms and legs combined. Aerobic capacity, aerobic power, functional capacity, functional aerobic capacity, maximal functional capacity, cardiorespiratory fitness, cardiovascular fitness, maximal oxygen intake, and maximal oxygen uptake are terms that are often used interchangeably.

Aerobic conditioning is regular physical training in aerobic activities over an extended period of time.

Aerobic fitness is the capacity to exercise in aerobic activities for a prolonged period where the amount of activity depends on aerobic capacity and cardiorespiratory endurance.

Agility is a skill-related component of physical fitness that relates to the ability to rapidly change the position of the entire body in space with speed and accuracy.

Anaerobic exercise is intense activity requiring energy production without using oxygen. Anaerobic means in the absence of oxygen.

Anaerobic threshold defines the upper limit of exercise intensity that can be sustained aerobically. The anaerobic threshold is attained during more intense exercise where anaerobic metabolism represents a significant proportion of the required energy supply. The onset of blood lactate accumulation (OBLA), aerobic-anaerobic threshold, individual anaerobic threshold, point of metabolic acidosis, and lactate threshold essentially mean the same thing.

Body composition is a health-related physical fitness component that relates to the relative amounts of muscle, fat, bone, and other vital parts of the body.

Cardiorespiratory endurance is a health-related component of physical fitness that relates to the ability of the circulatory and respiratory systems to supply fuel during sustained physical activity and to eliminate fatigue products after supplying fuel. Cardiorespiratory endurance is often used interchangeably with aerobic or cardiorespiratory fitness.

Chronic diseases are illnesses that are prolonged, do not resolve spontaneously, and are rarely curred completely (3).

Conditioning is regular exercise conducted over an extended period of time. Conditioning and training are the same.

Coordination is a skill-related component of physical fitness that relates to the ability to use the senses, such as sight and hearing, together with body parts in performing motor tasks smoothly and accurately.

Epidemiology is a discipline focusing on how diseases originate and spread in populations.

Exercise is planned, structured, and repetitive bodily movement done to improve or maintain one or more physical fitness components. Progressive overloading is necessary to improve specific fitness components. Exercise, conditioning, and physcial training are terms that are used interchangebly.

Exercise guidelines refer to the type and amount of activity specific to the intensity, frequency, and length of workouts needed to produce or maintain desired physical fitness outcomes.

Exercise intensity: The intensity for aerobic conditioning should range between 40 to 85 percent of aerobic capacity (1,2). Low- intense exercise is usually less than 50 percent. For some individuals who are less fit, cardiorespiratory endurance can be improved by conditioning at an intensity level that is as low as 40 percent of aerobic capacity (2). From a public health perspective, moderate-intense activities are between 3-6 METs (5). According to the ACSM, moderately-intense aerobic exercise is between 40 to 60 percent of aerobic capacity (1,2). Moderate aerobic exercise can be comfortably sustained up to 60 minutes if there is a gradual progression and the activity is generally noncompetitive. Subjectively, moderate-intense exercise causes little or no discomfort, little incease in breathing, and should be well within a person's capability.

Flexibility is a health-related component of physical fitness that relates to the range of motion available at a joint.

Health is a dynamic state ranging from chronic illness or disability to optimum levels of functioning in all aspects of life. Health has been defined as a human condition with physical, social, and psychological dimensions, each characterized on a continuum with positive and negative poles (from the 1988 International Consensus Conference on Exercise, Fitness, and Health). Within this definition, positive health is associated with life enjoyment and not merely the absence of disease. Negative health is associated with morbidity and at the extreme, premature death.

MET: One MET is the amount of energy expended sitting quietly at rest adjusted to body weight (1 MET = 3.5 ml oxygen consumed/kg of body weight/minute). Also equal to 1 kcal/kg/hour. Physical activity intensity is often expressed in MET units. For example, walking at a 14 minute pace per mile is expressed at an intensity of 6 METs or 6 times the energy sitting quietly at rest.

Morbidity is any departure, subjective or objective, from a state of physical or psychological well-being, short of death.

Muscular endurance is a health-related fitness component that relates to the amount of external force that a muscle can exert over an extended period of time.

Muscular strength is the ability of a muscle to exert force. Strength is a health-related fitness component that is assessed by the maximal amount of resistance or force that can be sustained in a single effort.

Physical activity is bodily movement produced by skeletal muscle contraction resulting in a substantial increase in energy expenditure (3,6). Physical activity has both an occupational and leisure basis that includes both active recreation pursuits like golf, tennis, and swimming. It also includes other active pastimes like gardening, cutting wood, and carpentry. Physical activity can provide progressive health benefits and be a catalyst for improving health attitudes, health habits, and lifestyle (7).

Physical fitness relates to a set of attributes that people have or achieve that determine the ability to perform physical activity. Physical fitness is the ability of the body to respond or adapt to the demands and stress of physical effort.

Physical performance is the ability to perform a physical task or sport at a desired level. Also called motor fitness or physical fitness. Physical performance depends on both skill and physical fitness. Physical fitness components can include aerobic and anaerobic power, agility, balance, coordination, flexibility, muscular fitness, and timing.

Power is a skill-related component of physical fitness that relates to the rate at which one can perform work. Power is the amont of work performed per unit of time.

Reaction time is a skill-related physical fitness component that relates to the time elapsed between stimulation and the beginning of reaction to it.

Skill-related fitness includes fitness elements such as agility, balance, speed, and coordination. While these elements are important for participation in various performance-related activities, they may have little significance for the day-to-day tasks of most people or their general health.

Speed relates to the ability to perform a movement within a short time period.

Vigorous-intense activitiy from a public health perspective, require an energy output in excess of 6 MET units (5). The ACSM classifies vigorous exercise at an intensity greater than 60 percent of aerobic capacity (1,2,). Exercise at this level can feel somewhat heavy to very heavy and often results in increased breathing and sweating. Vigorous nonstop exercise resulting in fatique within 20 minutes requires a considerable challenge to the cardiorespiratory system.

It isn't necessary to exercise vigorously to achieve better health. (However, exercise intensity level can continuously range from moderate and often exceed aerobic capacity for athletes who are competing in sports like rowing, swimming, cycling, running, basketball, soccer and lacrosse. "For these athletes, the optimal range of training intensities should include the range and pattern of intensity demands encountered in competition" (2, p 441).


Human Performance/Training-related Terms and Principles

Adenosine triphosphate (ATP) is the energy currency for biologic work. The chemical breakdown of ATP to ADP (adenosine diphosphate) produces an immediate energy source for muscular contraction.

Mechanical efficiency is the percent of total chemical energy produced that contributes to the actual work accomplished with the remainder lost as heat. The efficiency for cycling may be 20% while the efficiency for front crawl swimming ranges between 5 and 9.5%.

Metabolic fitness is the ability to provide energy (ATP) to the muscles during activity.

Movement economy is the energy required (usually measured as oxygen consumed) to maintain a constant movement velocity.

Oxygen deficit is the delay in oxygen consumption during exercise when the oxygen needed for energy production remains below the required amount. The deficit is greatest during short-term intense exercise when the energy is supplied anaerobically. This exercise induced oxygen deficit produces an excess post exercise oxygen consumption (EPOC) above the resting level even following mild activity. The EPOC is needed to restore the oxygen deficit and physiologic function to the resting state.

Phosphocreatine (PC, PCr) is an energy supplying chemical compound stored in muscle cells that anaerobically produces ATP for muscular contraction.

Training principles are guidelines that form the basis for exercise program development. The training principles are difined below.

Adaptation is the type of change in physiologic functions that occur with training, rest, and recovery.

Individualization means that training gains are based on a person's adapatation rate which is influenced by the type and amount of training stimulus, lifestyle habits like nutrition, genetics, age, sex, and disease conditions.

Maintenance refers to effectively sustaining avhieved training gains.

Overload means that the body adapts to the type and amount of training stimulus imposed and fitness gains are made by progressively increasing (same as progressive overload) the exercise load.

Progression is the change in adaptation response.

Retrogression or reversibility means that the loss of performance gains (same as detraining) occurs when training stops. Only 1 or 2 weeks of detraining can significantly reduce fitness gains and many training improvements can be totally lost within several months. The fitness gains from many years of training are temporary and reversible even among highly trained athletes.

Specificity means that the body adapts to the type and amount (volume and intensity) of exercise load and the primary energy system(s) engaged during the activity. For example, training specifically for muscular strength and power may only produce adaptations to those fitness components without improving cardiorespiratory fitness.


1. American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription (fifth edition). 1995: Williams & Wilkins.

2. ACSM's Resource Manual for Guidelines for Exercise Testing and Prescription (third edition). 1998: Williams & Wilkins.

3. Casperson CJ, Powell KE, Christenson GM. Physical activity exercise and physical fitness. Public Health Rep. 1985;100:125-131.

4. Howley ET, Franks BD. Health Fitness Instructor’s Handbook (third edition). 1997: Human Kinetics.

5. National Institutes of Health Consensus Development Conference Statement: Physical Activity and Cardiovascular Health. JAMA 1996; 17;276(3):241-246.

6. President's Council on Physical Fitness and Sports. Definitions: health, fitness, and physical activity. Research Digest. March 2000;Series 3 (9).

7. Shephard RJ. Exercise and lifestyle change. Br. J. Sports Med. 1988:23(1):12.