Exercise Physiology Definitions and Terminology
Following are some commonly used exercise physiology terms and their
definitions. You will come across many of these terms in subsequent chapters.
Aerobic: A process of producing energy that requires oxygen.
Aerobic Capacity: Total or maximal amount of aerobic work that can be done.
4 Overview of Physical Fitness
Aerobic Metabolism: Most of the energy needed to support exercise that goes beyond 3
minutes is provided by aerobic or oxidative energy metabolism. In other words oxygen is
required to produce energy.
Agility: Ability to change physical position with speed and accuracy.
Anaerobic: A process of producing energy that does not require the presence of oxygen.
Anaerobic Capacity: Total or maximal amount of anaerobic work that can be done.
Anaerobic Glycolysis: A process of breaking down glycogen stores without oxygen; lactate
(lactic acid) is the by-product of this process.
Anaerobic Metabolism: A type of energy metabolism that does not require oxygen.
Anaerobic Threshold: Transition point when aerobic metabolism can no longer meet the
energetic demands, and energy from sources independent of oxygen are required. This is
also the work rate at which blood lactate concentrations start to increase during graded
exercise.
Adenosine Triphosphate (ATP): Energy released from food is stored in the muscle in the
form of ATP. When ATP is broken down energy is released.
Balance: Ability to maintain equilibrium when stationary or while moving.
Cardiorespiratory Fitness: Ability of the heart, lung and blood vessels to transport oxygen
and to remove waste products from the exercising muscle.
Concentric Contraction: Shortening of the muscle as it develops tension. This type of
exercise is sometimes known as “positive exercise”.
Coordination: Ability to use the senses, such as sight, along with the functioning of a set
of muscle groups to complete an activity accurately. For example: hand-eye coordination
during rifle shooting.
Dynamic Exercise: Alternate contraction and relaxation of a skeletal muscle or muscles
causing partial or complete range of movement through a joint.
The Navy SEAL Physical Fitness Guide 5
Eccentric Contraction: Involves the lengthening of a muscle as it develops tension and is
also known as “negative exercise”. Eccentric contractions are used when resisting gravity
as is the case in walking down hill or down stairs.
Electrocardiogram (ECG): A tracing that shows the electrical activity of the heart.
Ergometer: Instrument used to measure work and power.
Ergometry: Measurement of work and power during exercise.
Exercise: Planned, structured, and repetitive movements performed to improve or maintain
components of physical fitness. The components include cardiorespiratory fitness,
muscle strength and endurance, flexibility and body composition (see Introduction).
Fartlek Training: An unstructured type of interval training for speed-work.
Flexibility: Controlled range of motion of a specific joint. The range is a function of elasticity
of the tendons, ligaments, and surrounding soft tissue. Control is a function of
strength at each degree of motion, especially at the end ranges.
Glycogen: A form of carbohydrates that is stored in the liver and in muscles for energy.
Glycolysis: Breaking down of simple sugars into simpler compounds (chiefly pyruvate
and lactate) for energy. This process is anaerobic.
Glycolytic: Pertaining to or promoting glycolysis.
Heart Rate: Number of heart beats per minute.
Interval Training: Very intense exercise bouts are alternated with rest or periods of low
intensity exercise. Exercise during intervals is typically anaerobic.
Isokinetic: Contraction of a muscle or muscle group which results in joint movement at a
constant angular velocity. For example: the arm stroke during free style swimming.
Isometric (Static): Muscle contracts without shortening or lengthening such that tension
is developed but no muscular work is performed; energy is lost as heat. There is no joint
movement during this type of exercise.
Isotonic (Dynamic): Muscle contracts and maintains constant tension by lengthening or
shortening.
Lactic Acid (lactate): A by-product of anaerobic metabolism.
Ligament: A band of fibrous tissue that connects bone to bone or bone to cartilage so as to
strengthen joints.
Maximal Oxygen Uptake (VO2max): A measure of aerobic fitness: the maximal rate of
oxygen uptake, and therefore aerobic energy utilization during exercise. Typically
expressed as liters per minute or milliliters per kilogram (kg) body weight per minute (ml/
min/kg).
6 Overview of Physical Fitness
MET (Metabolic Equivalent Unit): A unit used to estimate the metabolic cost of physical
activity. One MET is the energy used by an individual at rest. This is equivalent to 3.5
ml of oxygen consumed per kg body weight per minute.
Metabolism: Physical and chemical processes that maintain life.
Minute Ventilation: Volume of air breathed per minute.
Muscular Endurance: Ability of a muscle or muscle group to contract at a submaximal
force, usually against 50 to 60% of maximal resistance, over a period of time. Measured as
the number of repetitions completed.
Muscular Strength: Maximal force or tension generated by a muscle or muscle group.
Myoglobin: An iron containing muscle protein that is responsible for the reddish color of
various muscle fiber types.
Physical Activity: Movement by skeletal muscles that results in energy expenditure.
Physical Fitness: Ability to perform physical activity.
Plyometrics: Also known as explosive jump training. Muscles are rapidly stretched prior
to contraction. Examples include standing jumps, multiple jumps, etc.
Power: Ability of a muscle to quickly generate force over a very short period of time.
Examples include sprint starts, vertical jumps, kicks and throwing a punch.
Rating of Perceived Exertion (RPE): Measured using the Borg Category RPE Scale. As
exercise intensity increases, the RPE increases and in general it is closely associated with
physiological measures such as heart rate and oxygen consumption.
Reaction Time: Time taken between receiving a signal and reacting to it.
Respiratory Exchange Ratio: Ratio of carbon dioxide produced to oxygen consumed.
An indication of the primary energy source used during exercise.
Speed: Ability to perform a movement in a short period of time.
Strength: Ability of a muscle to contract against resistance and provide control throughout
the full range of motion.
Stroke Volume: Volume of blood pumped from the heart with each beat.
Tendon: A fibrous cord in which the fibers of a muscle end and by which the muscle is
attached to a bone or other structure.
Tidal Volume: Volume of air moved during one breathing cycle while inhaling or exhaling.
Following are some commonly used exercise physiology terms and their
definitions. You will come across many of these terms in subsequent chapters.
Aerobic: A process of producing energy that requires oxygen.
Aerobic Capacity: Total or maximal amount of aerobic work that can be done.
4 Overview of Physical Fitness
Aerobic Metabolism: Most of the energy needed to support exercise that goes beyond 3
minutes is provided by aerobic or oxidative energy metabolism. In other words oxygen is
required to produce energy.
Agility: Ability to change physical position with speed and accuracy.
Anaerobic: A process of producing energy that does not require the presence of oxygen.
Anaerobic Capacity: Total or maximal amount of anaerobic work that can be done.
Anaerobic Glycolysis: A process of breaking down glycogen stores without oxygen; lactate
(lactic acid) is the by-product of this process.
Anaerobic Metabolism: A type of energy metabolism that does not require oxygen.
Anaerobic Threshold: Transition point when aerobic metabolism can no longer meet the
energetic demands, and energy from sources independent of oxygen are required. This is
also the work rate at which blood lactate concentrations start to increase during graded
exercise.
Adenosine Triphosphate (ATP): Energy released from food is stored in the muscle in the
form of ATP. When ATP is broken down energy is released.
Balance: Ability to maintain equilibrium when stationary or while moving.
Cardiorespiratory Fitness: Ability of the heart, lung and blood vessels to transport oxygen
and to remove waste products from the exercising muscle.
Concentric Contraction: Shortening of the muscle as it develops tension. This type of
exercise is sometimes known as “positive exercise”.
Coordination: Ability to use the senses, such as sight, along with the functioning of a set
of muscle groups to complete an activity accurately. For example: hand-eye coordination
during rifle shooting.
Dynamic Exercise: Alternate contraction and relaxation of a skeletal muscle or muscles
causing partial or complete range of movement through a joint.
The Navy SEAL Physical Fitness Guide 5
Eccentric Contraction: Involves the lengthening of a muscle as it develops tension and is
also known as “negative exercise”. Eccentric contractions are used when resisting gravity
as is the case in walking down hill or down stairs.
Electrocardiogram (ECG): A tracing that shows the electrical activity of the heart.
Ergometer: Instrument used to measure work and power.
Ergometry: Measurement of work and power during exercise.
Exercise: Planned, structured, and repetitive movements performed to improve or maintain
components of physical fitness. The components include cardiorespiratory fitness,
muscle strength and endurance, flexibility and body composition (see Introduction).
Fartlek Training: An unstructured type of interval training for speed-work.
Flexibility: Controlled range of motion of a specific joint. The range is a function of elasticity
of the tendons, ligaments, and surrounding soft tissue. Control is a function of
strength at each degree of motion, especially at the end ranges.
Glycogen: A form of carbohydrates that is stored in the liver and in muscles for energy.
Glycolysis: Breaking down of simple sugars into simpler compounds (chiefly pyruvate
and lactate) for energy. This process is anaerobic.
Glycolytic: Pertaining to or promoting glycolysis.
Heart Rate: Number of heart beats per minute.
Interval Training: Very intense exercise bouts are alternated with rest or periods of low
intensity exercise. Exercise during intervals is typically anaerobic.
Isokinetic: Contraction of a muscle or muscle group which results in joint movement at a
constant angular velocity. For example: the arm stroke during free style swimming.
Isometric (Static): Muscle contracts without shortening or lengthening such that tension
is developed but no muscular work is performed; energy is lost as heat. There is no joint
movement during this type of exercise.
Isotonic (Dynamic): Muscle contracts and maintains constant tension by lengthening or
shortening.
Lactic Acid (lactate): A by-product of anaerobic metabolism.
Ligament: A band of fibrous tissue that connects bone to bone or bone to cartilage so as to
strengthen joints.
Maximal Oxygen Uptake (VO2max): A measure of aerobic fitness: the maximal rate of
oxygen uptake, and therefore aerobic energy utilization during exercise. Typically
expressed as liters per minute or milliliters per kilogram (kg) body weight per minute (ml/
min/kg).
6 Overview of Physical Fitness
MET (Metabolic Equivalent Unit): A unit used to estimate the metabolic cost of physical
activity. One MET is the energy used by an individual at rest. This is equivalent to 3.5
ml of oxygen consumed per kg body weight per minute.
Metabolism: Physical and chemical processes that maintain life.
Minute Ventilation: Volume of air breathed per minute.
Muscular Endurance: Ability of a muscle or muscle group to contract at a submaximal
force, usually against 50 to 60% of maximal resistance, over a period of time. Measured as
the number of repetitions completed.
Muscular Strength: Maximal force or tension generated by a muscle or muscle group.
Myoglobin: An iron containing muscle protein that is responsible for the reddish color of
various muscle fiber types.
Physical Activity: Movement by skeletal muscles that results in energy expenditure.
Physical Fitness: Ability to perform physical activity.
Plyometrics: Also known as explosive jump training. Muscles are rapidly stretched prior
to contraction. Examples include standing jumps, multiple jumps, etc.
Power: Ability of a muscle to quickly generate force over a very short period of time.
Examples include sprint starts, vertical jumps, kicks and throwing a punch.
Rating of Perceived Exertion (RPE): Measured using the Borg Category RPE Scale. As
exercise intensity increases, the RPE increases and in general it is closely associated with
physiological measures such as heart rate and oxygen consumption.
Reaction Time: Time taken between receiving a signal and reacting to it.
Respiratory Exchange Ratio: Ratio of carbon dioxide produced to oxygen consumed.
An indication of the primary energy source used during exercise.
Speed: Ability to perform a movement in a short period of time.
Strength: Ability of a muscle to contract against resistance and provide control throughout
the full range of motion.
Stroke Volume: Volume of blood pumped from the heart with each beat.
Tendon: A fibrous cord in which the fibers of a muscle end and by which the muscle is
attached to a bone or other structure.
Tidal Volume: Volume of air moved during one breathing cycle while inhaling or exhaling.