Exercise Physiology Definitions

Exercise Physiology Definitions

• Work is the application of force through a distance.
• Energy is the capacity to perform work.
• Power is the rate of performing work, measured as work done per unit of time.

Energy Production and Efficiency

• The mechanical efficiency of the body is the percentage of total chemical energy expended that contributes to external work.
• Efficiency is the ratio of work output to work input.
• ATP-PCr system produces ATP via the breakdown of phosphocreatine.
• Anaerobic glycolysis produces ATP via the breakdown of glucose in the absence of oxygen.
• The aerobic system produces ATP from glucose or fat in the presence of oxygen, occurring in the mitochondria.

Energy Systems and Processes

• Lypolysis is the breakdown of triglycerides into glycerol and free fatty acids.
• Electron transport chain is a series of chemical reactions in the mitochondria that transfer electrons from hydrogen atom carriers to oxygen.
• Steady state is a balance between energy required for work and ATP production via aerobic means.

Measurement and Testing

• VO2 max is the amount of oxygen consumed at maximum exercise intensity, representing the ability to attain a high level of aerobic performance.
• Submaximal VO2 is the amount of oxygen consumed at submaximal exercise intensity.
• Lactate is a by-product of glucose breakdown via anaerobic glycolysis.

Anaerobic Threshold and Ventilation

• Anaerobic threshold is the second inflection point on the curve, where lactate concentration is 4.0 mmol/L, representing the ability to maintain a high level of aerobic performance.
• Ventilatory threshold is the volume of air ventilated relative to the amount of oxygen consumed (increases as exercise intensity increases).

Muscle Fibres and Respiration

• Type I fibres are slow twitch oxidative, best for long duration, low intensity activity.
• Type IIa fibres are fast twitch oxidative, best for short duration, high intensity activity.
• Type IIb fibres are fast twitch glycolytic.
• Ventilation is the movement of air into or out of the lungs.
• Respiration is the exchange of oxygen and carbon dioxide via diffusion.

Other Key Concepts

• Diffusion capacity is the volume of gas that diffuses through a membrane per minute at a pressure gradient of 1 mmHg.
• Forced vital capacity (FVC) is the volume of air that can be forcibly exhaled from the lungs after inspiring minimally.
• Forced expiratory volume in one second (FEV1) is the volume of air that can be forcibly exhaled from the lungs in the first second of a forced expiratory manoeuvre.
• FEV1% is the ratio of FEV1 to FVC, indicating what percentage of the total FVC was expelled from the lungs during the first second of forced exhalation.
• Partial pressure is the pressure exerted by each individual gas in a gas mixture.
• Myoglobin is found in skeletal and cardiac muscle fibres, transporting oxygen to mitochondria and releasing oxygen at very low partial pressure.

Motor Units and Control Systems

• Motor unit is a motor neuron and all the specific muscle fibres it innervates.
• Oxygen deficit is the lag in oxygen uptake that occurs at the beginning of exercise or when the exercise intensity increases.
• Homeostasis is the maintenance of a constant internal environment under normal resting conditions.
• Steady state is the maintenance of a constant internal environment under exercise conditions.
• Biological control system is a series of interconnected components that serve to maintain a physical or chemical parameter of the body at a near or constant value.

Other Key Terms

• Muscular contraction involves the transformation of chemical energy (ATP) to mechanical energy (movement).
• ATP is a high-energy compound consisting of one adenosine molecule and three phosphates with energy stored between the phosphate bonds.
• 1st Law of Thermodynamics states that energy cannot be created nor destroyed, but transferred from one form to another.
• Post-exercise oxygen consumption is the phenomenon where the body continues to engage in energy expenditure at elevated rates while cooling down back to homeostatic levels after an intense workout.
• All-or-none principle states that if the stimulus is strong enough to trigger an action potential in the motor neuron, all of the fibres in that unit are stimulated to contract.
• Maximal voluntary ventilation (MVV) is a measure of the maximum amount of air that can be inhaled and exhaled within one minute.
• Cardiac cycle is the repeating contraction and relaxation of the heart.
• Systole is ventricular contraction, while diastole is ventricular relaxation.
• Cardiac output is the volume of blood pumped from the ventricles each minute.
• Stroke volume is the volume of blood pumped out of the ventricle during systolic contractions.
• Ejection fraction is the fraction of end-diastolic volume ejected during ventricular systole.

Acid-Base Balance

• Acidosis is an abnormal increase in blood hydrogen ion concentrations and therefore a decrease in pH.
• Metabolic acidosis is a decrease in plasma pH below 7.1 caused by the addition of acid other than carbonic acid (e.g. lactic acid).
• Respiratory acidosis is a decrease in plasma pH below 7.1 caused by the addition of carbonic acid (by decreased alveolar ventilation).