Open Textbook of Exercise Physiology

a small collection of neurons involved in regulation of ventilation and located in the rostral ventrolateral medula and ventral respiratory column.  These neurons are involved in the response to hypxia.

preBötzinger complex

interneurons of the ventral respiratory group of the medulla that participate in generation of the respiratory rhythm.

effectively the ending of a burst of action potentials on a neuron or nerve complex. An example of burst termination is the end of the repeated action potentials activating the inspiratory muscles which will allow relaxation of the inspiratory muscles.

the ion pump that transfers Ca²⁺ across the cell membrane, using ATP for the source of energy. There are two important Ca²⁺ ATPases in skeletal muscle: one in the surface membrane and one in the sarcoplasmic reticulum membrane (also called sarco-endoplasmic reticulum Ca²⁺ ATPase or SERCA). Typically, two ions are transported for each ATP hydrolyzed.  There are three isoforms of SERCA. SERCA1 is in fast-twitch skeletal muscle. SERCA2 is in slow-twitch skeletal muscle and the heart.  SERCA3 is in smooth muscle (vascular and gut). 

a mathematical approach to describing the passive spread of current along a cell membrane. This theory is particularly important for predicting the spread of current associated with excitatory and inhibitory input to dendrites.

ion channels that permit Ca²⁺ to cross a membrane, down its electrochemical gradient. These can be in an external membrane, as in the dihydropyridine receptor, or in an internal membrane, as the ryanodine receptor of the sarcoplasmic reticulum. The dihydropyridine receptor is a modified Ca²⁺ channel that functions in skeletal muscle to link the action potential at the surface membrane and transverse tubule with molecular events within the cell. Wikipedia

refers to the relative effectiveness of Ca²⁺ in activating a process. In the case of skeletal muscle contraction, Ca²⁺ sensitivity can be interpreted by the half-maximal myoplasmic [Ca²⁺] with respect to force. When the myoplasmic [Ca²⁺] at half-maximal force decreases, then Ca²⁺ sensitivity has increased. Essentially this means that when Ca²⁺sensitivity increases, there will be more force at a given submaximal [Ca²⁺].  

Ca²⁺ concentration rises and falls with each activation of a skeletal muscle cell.  This rise and fall is called the calcium transient.  At low frequencies of stimulation, the [Ca²⁺] returns to rest levels between activations, but some Ca²⁺ will remain bound to molecules within the myocyte.  At high frequencies of stimulation, the [Ca²⁺] will not return to rest level, so the term transient can refer to a multi-stimulation event.

a small Ca²⁺-binding protein, similar to troponin, that exists in several cell types. Calmodulin which has four Ca²⁺-binding sites, participates in regulatory processes that are activated by increasing [Ca²⁺]. For example, the enzyme myosin light chain kinase is activated by calmodulin when it has 4 Ca²⁺ ions bound to it. Wikipedia.

the number of kilocalories of energy released per litre of oxygen consumed. In general, the caloric equivalent per litre of oxygen will be between 4.69 and 5.05, depending on the mix of substrate (fats, carbohydrates, and protein) oxidized.  

conventional unit of energy (heat).  Often used to quantify energy equivalent of food.  One calorie is equal to the energy needed to raise the temperature of 1 gram of water (at sea level) by one degree centigrade from 14.5 to 15.5°C. This is equivalent to 4.1855 joules. One kilocalorie is equal to the energy needed to raise the temperature of 1 kilogram of water (at sea level) by one degree centigrade from 14.5 to 15.5°C.  One kilocalorie is often expressed as one Calorie.  The capital “C” indicates the difference from one calorie. Wikipedia

a protein that binds Ca²⁺ in the sarcoplasmic reticulum, storing large amounts of this ion for activation of the myocyte.  Calsequestrin is localized to the terminal cisternae, the specialized part of the sarcoplasmic reticulum that is located adjacent to the transverse tubule.  Wikipedia

the professional organization representing educators in the fields of health, physical education and recreation.  

the professional organization of medical doctors in Canada. This organization promotes health among physicians and provides guidelines for working conditions of medical doctors in Canada.  CMA

a government sponsored program focused on monitoring regular physical activity of Canadians and promoting evidence-based lifestyle changes that promote health and longevity.  CFLRI

the former organization of academics involved in the study of sport science in Canada.  This organization changed its name to the Canadian Society for Exercise Physiology in 1992.  

a unique series of tests that could be conducted at home without professional supervision or interpretations.  

an organization of academics, involved in the study and teaching of exercise physiology. The CSEP membership includes certified personal trainers and certified exercise physiologists, practitioners of exercise administration for Canadians. CSEP regulates and provides the means for obtaining these certifications. CSEP also has established the physical activity guidelines for Canadians as well as the sedentary living guidelines. The CSEP also provides the questionnaire for clearance to increase the amount of physical activity that someone is engaged in, the PAR-Q+. CSEP has introduced “Exercise is Medicine” to Canada. CSEP

cancer is a disease that results from uncontrolled or abnormal growth of a tissue in the body.  This unusual growth has the capacity to invade normal tissue and spread to other tissues of the body (malignant).  In contrast, a benign tumor does not spread to other tissues.  Wikipedia

the amount of charge stored in a structure for a given potential difference between sides.  A membrane has a capacitance that is proportional to it's area. The lower the capacitance, the greater the change in voltage for a given charge movement. 

a structure that can hold a charge or store electric energy is called a capacitor. 

blood vessel of the microcirculation.  Exchange of gas (O2 and CO2) as well a small molecules and water occurs across capillary walls.  These blood vessels are typically large enough to allow red blood cells to pass through (~7mm diameter) and usually not more than 1 mm in length.  Capillary walls are one endothelial cell thick and allow transfer of water, ions, gases, metabolic substrates and products of metabolism.  

an organic biomolecule consisting of carbon, hydrogen, and oxygen. Carbohydrates, including: fibre, starch, glycogen, monosaccharide, and disaccharide are in the food we eat. We absorb these from the gastrointestinal system as simple sugar and either store them as glycogen or use them for metabolism. Carbohydrates provide 4kcal×g^-1 of energy. Glucose is the most common monosaccharide in the body and represents an important substrate for aerobic and anaerobic metabolism. Wikipedia

an exercise and diet procedure that is used by athletes in an attempt to increase glycogen stores in muscle beyond the normal level. This is an important procedure to assure optimal performance in any endurance event that would otherwise deplete muscle glycogen, typically for an event lasting more than 90 min. The procedure involves a few days of reduced volume of training and a diet that is high in carbohydrate. Wikipedia

the catabolic metabolism of carbohydrates (sugars, glycogen) to replenish ATP in the body.  Glycolysis is the name of the sequence of chemical reactions that glucose follows. This is followed by the Krebs Cycle.  The end product of oxidative metabolism of glucose is CO₂ and H₂O, in addition to the chemical energy preserved in ATP.

the volume of carbon dioxide produced in the body each minute. The VdotCO₂ is usually measured as pulmonary release of carbon dioxide but can also be measured with sampling of arterial and venous blood and measurement of blood flow (Fick equation). The pulmonary measurement of carbon dioxide production, also referred to as carbon dioxide output, is only valid when total body stores of CO₂ are constant. This condition is not satisfied during exercise above the anaerobic threshold and is certainly not valid during early recovery after such high intensity exercise.

the volume of blood pumped by the left ventricle each minute, abbreviated as Q(with a dot over the Q). This is the volume of blood going to the tissues of the body each minute, and can be calculated as heart rate times stroke volume (the volume of blood ejected from the heart with each cardiac cycle). Coincidentally, this is also the volume of blood transported through the lungs each minute. Wikipedia

a measure of fitness that relates to the ability of the cardiovascular and respiratory systems to deliver oxygen to the active muscles of the body. Maximal oxygen uptake is considered the best measure of cardiorespiratory fitness.

chronic disease affecting function of the heart and/or blood vessels.  Typically, cardiovascular disease is atherosclerosis or hardening or blocking of the arteries. Atherosclerosis of coronary arteries can cause angina and precipitate a heart attack.  Rupture or occlusion of blood vessels in the brain is called a stroke.  Wikipedia

an amino acid that functions in the liver and skeletal muscle for transport of acyl groups across mitochondrial membrane.  

rubbery substance that covers the ends of bones, providing a buffer for bone to bone contact.  Cartilage is somewhat elastic, deforming when bones are pressed together and rebounding when the load is removed.  In addition to living cells, the cartilage is composed of proteoglycans, collagen, glycosaminoglycans and elastin.

a higher sustained force is achieved at a given frequency of activation when the first 2-3 pulses (doublet or triplet) are at a higher frequency.  This pattern of activation is typical for ballistic contractions.

a classification of monoamines that relates to autonomic function in the body. The catecholamines include dopamine, epinephrine and norepinephrine, also known as adrenaline and noradrenaline. Dopamine is a neurotransmitter in the central nervous system. Norepinephrine is secreted locally by sympathetic neurons and into the blood by the adrenal gland. Epinephrine is secreted into the blood by the adrenal gland.  The catecholamines interact with receptors on a variety of cells in the body. The cellular impact of reaction of catecholamines with these receptors varies from cell to cell. Wikipedia.

immunity obtained from the presence of cells that can destroy or consume debris and foreign substances. T-lymphocytes are examples of cells that participate in cell-mediated immunity.  Wikipedia  

A blue tinge to the skin or mucous membranes of the mouth resulting from a high concentration of deoxygenated arterial blood.  

the brain and spinal cord.  The nervous system is divided into central and peripheral branches.  The peripheral nervous system includes all neural tissue that lies outside the brain and spinal cord.  Wikipedia

central controller

a control system that operates from the central nervous system

central locomotor command hypothesis

the theory that the central nervous system has locomotor pattern generators that regulate the appropriate sequence of activations of muscles of locomotion. Triggering these pattern generators will evoke movements associated with typical locomotion without the requirement for repeated voluntary engagement.

Central Pattern Generator (CPG)

a property of a locus of neurons that are capable of causing a consistent response like a repeating burst without a similar input. Modulating signals can change the frequency or bursts or the frequency within the burst.

in the dichotomy of central vs peripheral with respect to the cardiovascular system, central refers to the heart, large arteries and large veins.  In contrast, peripheral refers to the remaining vessels of the cardiovascular system.

a statistical term referring to a single measure or estimate representing the middle of a number of values. Mean, median and mode are the measures of central tendency. Wikipedia

see Canadian Fitness and Lifestyles Research Institute

sensors in the body that respond to specific molecules are called chemoreceptors. These can be within the vascular system, like the arterial chemoreceptors in the arch of the aorta or the carotid chemoreceptors. There are also chemoreceptors within the brain ( central chemoreceptors) and in other tissues including muscle. Chemoreceptors in muscle provide feedback to the brain via type IV afferent neurons.

chemokine (noun)

protein secreted as part of an inflammatory reaction with responses associated with guiding immune cells to the area

chemotaxis

the migration of cells, triggered by some chemical attractant.

see Canadian Home Fitness Test

a fat (sterol) that serves as a precursor for steroid hormones and is a key component of membranes. Cholesterol can accumulate in the blood and is typically transported in association with lipoproteins. Deposition of cholesterol and other fats on the inside walls of arteries leads to atherosclerosis. This deposition is associated with low density (LDL) and very low-density lipoproteins (VLDL). Resorption or fats from these depositions can occur by circulating high density lipoproteins (HDL). Wikipedia

an enzyme that removes choline from a conjugated molecule. Acetylcholinesterase is a common cholinesterase that removes choline from acetylcholine, resulting in the formation of acetate and choline. This activity terminates neuromuscular transmission.  

found in the nucleus, the 23 pairs of chromosomes (in human) carry the genetic information.  Each chromosome is a string-like structure of nucleic acids (DNA) and proteins.  Division of the chromosomes is the basis for cell division.

a medical condition that develops over time and persists for a long time.  Chronic diseases include: arthritis, diabetes, heart disease, asthma, and cancer.  Wikipedia

the sequence of reactions that begins with combining acetyl CoA with oxaloacetate to form citric acid, which is subsequently converted back to oxaloacetate by a sequence of reactions that result in formation of Guanosine triphosphate, CO₂ and NADH. Wikipedia

a nomenclature system to categorize cells with immune function, based on the types of molecules it can bind to.  

coming soon

also, cerebral function; the ability to think, learn and recall knowledge.

string-like extracellular protein, a major structural part of connective tissue.  Collagen is made by fibroblasts and is a substantial part of endomysium. Wikipedia

two or more protein sources that together provide a complete amino acid profile (e.g. adequate amounts of all essential amino acids).  

a part of the innate immune system that enhances the ability of phagocytes to perform their function; ingest and digest foreign elements including debris. The complement system includes a number of small proteins that have been synthesized in the liver and circulate in the blood in an inactive form.

change in length divided by change in force; the opposite of stiffness. Tendon compliance refers to the ease with which tendon is stretched.

a type of contraction during which shortening occurs. This is a type of dynamic contraction also known as a shortening contraction. Wikipedia

composed of airways that are not involved in gas exchange and are simply responsible for the movement of air from the external environment to the transitional and respiratory zones.

the conveyance of something, such as heat, by contact. We warm (or cool) the air or water around us by conduction. Similarly, we would warm any surface that we were in contact with. When you get up from your seat in a cold stadium, the seat will be warm because you have transferred heat to it. In the short term, this will result in a cold bum. Wikipedia

Conductance

The ease with which flow occurs; this could be flow of blood through part or all of the vascular system, or the flow of ions through a membrane etc. Conductance is inversely related to resistance.

having the effect of disturbing or altering the outcome. For example, a confounding variable would be an influence that could alter the outcome of an intervention under experimental consideration.

the tissue between specialized cells of the body. Connective tissue is present in all organs of the body: brain, heart, skin, muscle and abdominal organs. Connective tissue is made up of cells (fibroblasts, interspersed with elastin and collagen).  

the measured content (in ml%) of oxygen in the mixed venous blood.  Mixed venous blood indicated by a dash over the v, is typically sampled from the right ventricle or pulmonary artery.  

venous oxygen content

without the dash over the v, (CvO2) is content of venous oxygen for any vein in the body.

that portion of a muscle representing the collection of proteins that generate force and/or movement.  Often used in modeling, the term “contractile element” refers collectively to the sarcomeres of the muscle; those parts that interact to generate force or movement with the use of chemical energy.

refers to actin and myosin in skeletal muscle. Myosin-2 is a molecular motor that interacts with actin to produce force and/or movement in our muscles. Myosin is actually a superfamily of molecular motors that serve to move cells and parts of cells throughout the animal kingdom.  There are also molecular motors in other tissues, like the axon of neurons.  These molecular motors (kinesin and dynein) which function to transport proteins and organelles along the axon, using microtubules as tracks.

Contractile tissue includes the heart, skeletal muscles blood vessels and gut. when activated, contractile tissue will undergo contraction. This means that myosin will interact with actin, and ATP will be split to form ADP and Pi. This will result in force development and/or shortening.  

heat loss to the environment can occur by convection. This is when the substance immediately around you is constantly replaced, such as when the wind is blowing and the air that you warmed by conduction is replaced. Convection allows continuous heat loss (or gain if you are in a hot-tub). Wikipedia

convective (adjective):

relating to flow or movement; 

convergence

coming together. several sources come together to form fewer streams. Convergence in neural physiology refers to input from several neurons connecting with a common target neuron. In the vascular system, convergence would be several blood vessels joining to allow their flow to go through fewer vessels. The opposite of convergence is divergence.

vascular disease of the coronary vessels. Vascular disease typically means a build-up of plaque and calcification in the internal wall of vessels, particularly arteries. This progresses to thickening of the smooth muscle layer and restriction of the lumen. When blood flow is restricted, relative ischemia can occur. This ischemia is detected as pain, known as angina. NIH

a measure of the strength of the relationship or interdependence between two variables. A correlation tells you how closely two variables or measurements change in tandem. Wikipedia

a class of steroid hormone, secreted by the adrenal cortex, that has effects on glucose and electrolyte balance including glucocorticoid, cortisol, and aldosterone. Wikipedia

one of the corticosteroid hormones secreted by the adrenal cortex. Cortisol is released when the body is under stress or when blood glucose is decreased. One of the key functions of cortisol is to increase gluconeogenesis by promoting protein catabolism, making amino acids available to the liver for synthesis of new glucose. Wikipedia

a specific protein produced by the liver that circulates in the blood and increases in concentration during an inflammatory response.  CRP is an acute-phase protein and is often used to detect an immune response in the body.  Wikipedia

a small nitrogen-containing molecule that when bound with phosphate can serve as an immediate supply of energy, transferring the phosphate to ADP to form ATP. Creatine is a popular supplement for strength training athletes and is used in therapy for several pathologies. Wikipedia

creatine kinase (CK)

an enzyme that catalyzes the reaction: ADP + Creatine phosphate  <=>  ATP + Creatine. A kinase always transfers a phosphate between molecules. There are two isoforms of CK; one located in the membrane of the mitochondria which favours the above reaction to the left (forming creatine phosphate) and one in the myofibrils that favours the above reaction to the right, forming creatine.  

also known as creatine phosphokinase

creatine phosphate

a high energy phosphate molecule that serves to buffer ATP concentration by the creatine kinase reaction.  Creatine, formed in the myofibrils can diffuse to the intermyofibrillar mitochondria where creatine kinase removes a phosphate from ATP, giving it to creatine, forming creatine phosphate. This newly formed creatine phosphate can diffuse to the myofibril.  This movement of creatine and creatine phosphate is referred to as the creatine shuttle.

a breakdown product of creatine. A very small proportion of creatine is converted to creatinine each day. The kidneys dispose of creatinine by filtration, without further exchange in the distal convoluted tubules. Therefore, measurement of creatinine in the blood and urine allows estimation of the glomerular filtration rate. 

a unique feature of skeletal muscle is that adjacent cells are linked at recurring structures called costameres. The costameres join myofibrils at the Z-disk and extend into the connective tissue around each cell (endomysium) to connect with adjacent myocytes at their Z-disk. The costameres align myofibrils and myocytes to give skeletal and cardiac muscle a striated appearance because the sarcomeres are aligned.

the asymptote of the relationship between power and endurance, obtained by completion of at least three time-trials selected in anticipation of completion in 3 to 15 min. This power output is thought to represent the highest intensity of exercise that can be sustained by aerobic metabolism. Critical power can also be determined as the slope of the relationship between work and endurance in the same time-trials. See critical speed.  

the asymptote of the relationship between speed and endurance, obtained by completion of at least three time-trials selected in anticipation of completion in 3 to 15 min. This speed is thought to represent the highest intensity of exercise that can be sustained exclusively by aerobic metabolism. See critical power.  

when the myosin head binds to actin, it forms a cross-bridge. This binding between actin and myosin initiates release of inorganic phosphate (Pi) and results in a conformational change to the myosin configuration that causes force generation and/or motion. The myosin head is the molecular motor of muscle function.

proposed by A.F. Huxley, the cross-bridge theory explains how muscle contraction occurs. The general idea is that projections off the myosin (thick) filaments indepedently interact with the actin (thin) filaments and pull these filaments towards the middle of the sarcomere when the muscle is activated.

a measure of the rate of cycling of cross-bridges. The units would be s^-1, indicating the number of unitary cross-bridge cycles per second.  

a classical experimental approach to demonstrate the capability of changing fibre type within a muscle. In this animal study, the nerve of one muscle is cut and inserted into a muscle of different fibre type. Complete cross-reinnervation would involve also cutting the nerve of the second muscle and inserting it into the first muscle. The animal is allowed to recover, and the contractile properties of the experimental muscles are evaluated, revealing that they have changed fibre-type composition.  

physical activity and health variables are measured at the same point in time across different populations of subjects and the researchers examine whether the variables are related or vary between the populations.

a reflex extension that originates from sensory input from the opposite side. The reflex typically results in leg extension when the opposite leg experiences pain. The end result of this action is withdrawal from the pain-inducing stimulus while allowing support of the body by the opposite limb.

the rate at which charged particles moves along a specific path, or past a certain location. 

finding the appropriate constants for an equation that allows a close fit of the line described by an equation and the pattern shown by two variables. Typically, curve-fitting will be done by the method of least squares. That is, a variety of values for the constants will be tested and the values that give the smallest discrepancy (squared) between the actual measured values. Wikipedia

small molecules released from various tissues and having regulatory function on the same tissue or other tissues.  For example, muscle can release cytokines that affect muscle growth and development, but also can effect nerve changes

cytoplasm:

the fluid/gelatinuous contents of a cell, excluding the nucleus.

an internal frame, like that for a tent, but for individual cells.  The cytoskeleton is formed with several proteins including actin, actinin, desmin, dystrophin and many more. Cytoskeletal proteins participate in several cellular functions, including: giving the cell shape, allowing motion, cell division, mechanical transduction and force transfer.