max to pH

the highest value for oxygen uptake per minute that can be achieved by an individual.  This is often taken as the highest 30 s average during an incremental exercise test.  The criterion for reaching true (O₂ is when (O₂ does not increase when exercise intensity increases.  Wikipedia

the mathematical average, or sum of all values divided by the number of samples.

lateral pressure in the arteries, averaged over time.  Mean arterial pressure is estimated by diastolic pressure plus one third of pulse pressure where pulse pressure is the difference between systolic and diastolic pressures.

mean pulmonary arterial pressure

average lateral hydrostatic pressure in the pulmonary artery.

interactions or influences between systems that are dependent on physical factors that affect function. For example, pressure changes in the chest cavity due to breathing can influence venous return to the heart. 

sensors within the body that detect motion, length, force, or pressure. Mechanoreceptors include: muscle spindles, Golgi tendon organs, and Pacinian corpuscles as well as undefined nerve endings in muscle that are sensitive to motion.  Rapid adaptation of these undefined nerve endings results in only transient firing when exercise is started.

mechanoreceptor/metaboreceptor hypothesis

coming soon

a measure of central tendency that is represented by the middle value when all values are ranked from lowest to highest. Other measures of central tendency include mean and mode. Wikipedia

the measured voltage difference across a membrane. Typically, the membrane potential for a muscle or nerve cell is about -85 mV, measured with the extracellular space as a reference. When the membrane potential is more negative than this, it is considered to be hyperpolarized. When the difference is less, it is depolarized.

membrane resistance

the magnitude with which current is impeded in travelling across a cell membrane. Membrane resistance is dependent on the integrity of the membrane and the availability of (opened) ion channels.  Membrane resistance (R) is proportional to ion flow (I) and the voltage difference across the membrane.

maintaining an appropriate state of psychological well-being or able to function suitably in terms of emotional and psychological state.  Wikipedia

statistical evaluation of the evidence from several published studies.

one MET is considered equivalent to resting metabolic rate or 3.5 ml×kg^-1×min^-1.

METs

plural of MET (metabolic equivalent)

a chemical substance that serves as the starting point for energy metabolism in the body. Fatty acids and glucose are the primary metabolic substrates; these chemicals are converted to water and CO₂, and in the process, some of the energy released is conserved in chemical energy of adenosine triphosphate (ATP). 

intermediate product of metabolism or chemical process in the body. A metabolite can be a building block for protein synthesis (amino acid) or a small molecule that serves as a signaling substance. 

neural receptors that are sensitive to metabolic products in the interstitial space. Metabolic products include CO₂, potassium, and H⁺.

metaboreceptor/mechanorecptor hypothesis

control of cardiovascular responses to exercise are apparently regulated by afferent input from metaborecptors and mechanoreceptors located in muscles. 

a reflex increase in ventilation and circulation in response to increased metabolic rate. Stimulation of the metaboreceptors is thought to be the triggering event.

a membrane protein that responds when the appropriate ligand binds to it by a cascade of reactions resulting in second messenger response within the cell. an example of a metabotropic receptor is the insulin receptor that mobilizes GLUT-4 receptors to the membrane when insulin binds to this receptor.

a category of nutrients that are required by the body in small amounts. Includes vitamins and minerals.  healthline

when exercise intensity is called “mild”, it involves a small relative increase in metabolic rate above resting level.  Mild intensity exercise could typically be sustained for more than 6 hours. 

inorganic substances (atoms or elements) required for life in relatively small amounts. There are 21 minerals required for human health.  

the amount of air moved into (VdotI) or out of (VdotE) the lungs in a minute. VdotE  represents measured volume of air expired in one minute). For example, at rest an adult might breathe 12 times in a minute with an average tidal volume of 500 ml. Their minute ventilation would be 6000 ml or 6 litres. It is standard to express all volumes of the human body at body temperature and pressure, saturated. This requires knowledge of the conditions under which the volume was measured and conversion to the body temperature (310° K), pressure (atmospheric pressure) and saturated water vapour pressure.

plural of mitochondrion, an organelle with a double membrane that contains the enzymes needed for oxidative metabolism.  Mitochondria exist in most cells of the body, but are more prevalent in tissues with a high metabolic rate like skeletal and cardiac muscle tissue.  Mitochondria use O2 to transfer chemical energy in substrates like fat and carbohydrate to ATP which can be used in the cell for processes that require energy. Wikipedia

in or associated with the mitochondria. 

the cellular process of increasing mitochondrial mass and copy number. This process is coordinated by both the nuclear and mitochondrial genomes as most of the mitochondrial proteins are encoded by nuclear genes.

biogenesis: 

the generation of tissue; synthesis of the proteins and structures for a given tissue, commonly used in reference to mitochondria

the amount of oxygen bound and dissolved in a volume of mixed venous blood. Mixed venous blood is a mixture of blood returning from all organs and tissues to the heart and is well represented by a sample of pulmonary artery blood. Oxygen content is typically given in ml % or ml of oxygen per 100 ml of blood. It is functionally more useful to present the value in ml of oxygen per litre of blood. This value is 10 times the ml % value.

oxygen content

the volume of oxygen in a given volume of blood; CaO2 is content of arterial blood

that portion of the gas pressure contributed by carbon dioxide. The gas pressure of a fluid is equal to the total air pressure exerted on the surface of the fluid. The portion of the pressure exerted by one gas (carbon dioxide in this case) is proportional to the fraction of the atmosphere around that surface occupied by the gas in question. Partial pressure is one important factor dictating the content of a gas in a fluid, but solubility and binding within the fluid can change the total amount of a gas at a given partial pressure.

the most commonly occurring value in a set of measurements. When the values are distributed normally (frequency histogram has a Bell shape), mode, median, and mean will be close in value.

an intensity of physical activity that can typically be sustained for 1 to 3 hours, or jus below the aerobic threshold The most cited activity that defines this intensity is a brisk walk. Walking slower would be considered mild intensity exercise. Jogging or running would be considered vigorous intensity (or higher). WHO

this is the range of exercise intensity that is often referred to for exercise prescription for health benefits.  This range is from a little below the aerobic threshold to the anaerobic threshold.  The exercise intensity range that is recommended for health benefit.  On a scale that includes mild exercise that can be sustained for hours and hard exercise that can be sustained for less than 30 min, moderate to vigorous exercise is between these extremes.  Moderate exercise can typically be sustained for more than an hour while vigorous exercise can probably be sustained for less than an hour.  A brisk walk would be considered moderate exercise while a jog would be considered vigorous.

the angular force applied; calculated as tangential force times the motor arm, measured as the perpendicular distance between the centre of rotation and the line of action of the force. Synonymous with torque.

the relationship between moment (tangential force times the moment arm) and angular velocity.  This relationship is synonymous with the force-velocity relationship, but applies to in vivo circumstances, usually measured over a limited range of angular velocities. 

small molecules having single carboxylate group, like lactate and pyruvate. A carboxylate group is a single carbon with two oxygen molecules (COO). A monocarboxylate is a salt molecule, the acid being the condition where one of the oxygen molecules has a hydrogen bound to it (COOH). 

a neural pathway typically involving the affector (sensory) neuron synapsing with the effector (motor) neuron. The stretch reflex is an example of a monosynaptic reflex. The Ia afferent neuron synapses directly with the alpha motor neuron, 

adjective, describing structure having to do with life. A morphological description of the body would describe the shape, texture and form. Morphology (noun).

study of the structure  and form of a biological body or part thereof.

chemical, structural and functional changes in the body that occur in response to challenges to the homoestatic condition; these changes assist in preservation of homeostasis when this circumstance subsequently occurs

morphological adaptation: changes in body size or proportion that occur in response to some environmental circumstance or chronic stress of that body or body part.  

refers to the tendency to die.  Mortality rate is often used to study the impact of behaviours or conditions that alter the death rate in a population.

a collection of cell bodies in the ventral horn of the spinal cord that connect to a single muscle.  These neurons and the muscle cells connected to them form the motor units of the muscle in question.

a motor neuron and all muscle fibres innervated by that motor neuron. Motor unit size can vary between muscles and within a muscle.   Wikipedia

initiation of activation of a motor unit or a collection of motor units. Activating an increased number of motor units.  Force of contraction can be increased by either motor unit recruitment or by rate-coding (increased frequency of activation of motor units). 

a muscle with complex structure where there are several angles of fibre orientation, relative to the line of action of the muscle

 Adaptation refers to muscles ability to change its physiological and metabolic functions when stressed; for example, when exercising.  Adaptation results in improved ability to maintain homeostasis.

the nature of the structure of muscle in terms of protein content. In particular, muscle composition often refers to fibre-type or relative proportion of fast-twitch and slow-twitch muscle fibres present.

sensory organ of the muscle that is sensitive to length and rate of change of length.  A spindle is composed of 1 or more bag fibres and several nuclear chain fibres.  The bag fibres are innervated by type Ia afferent neurons and the chain fibres are innervated by type IIa afferent fibres.  Efferent innervation of the spindle is by  g amma motor neuron.

the ability of the muscle or muscle group to generate force.  Muscle strength is typically measured in isometric contractions and is usually measured as a moment, not taking into consideration differences in moment arm that influence moment for a given force.

muscle tissue is a collection of muscle cells (myocytes) or portions of such cells; this can be smooth, cardiac or skeletal muscle.  Muscle tissue would be different from bone or tendon or organ tissue.

a fatty substance, synthesized by glial cells in the central nervous system and by Schwann cells in the peripheral nervous system.  The glial cells and Schwann cells wrap around the axon and the myelin serves as an insulator, preventing ion exchange across the axon membrane; this slows conduction velocity of action potentials.

a haeme-containing molecule that binds oxygen and is present in muscle.  Diffusion of oxygen is facilitated by myoglobin. Myoglobin, like haemoglobin, is red in colour and gives dark meat it’s reddish colour. Muscle with high oxidative capacity has a high concentration of myoglobin. 

an assessment of the capabilities of the musculoskeletal system. This assessment could include: muscular strength, muscular endurance, and bone mineral density.

a muscle cell (also a fibre). Like most cells of the body, a myocyte contains several organelles, however because the myocyte is often quite long (can be several cm long in adult human muscle), the myocyte contains multiple nuclei and a substantial volume of the cell is occupied by mitochondria.  Much of the cell volume is occupied by myofibrils which contain the contractile proteins.

a tubular organelle in skeletal and cardiac muscle composed of sequential sarcomeres.  Each myofibril is about 1 µm in diameter and can run the full length of the myocyte.  The sarcomere is from Z-disk to Z-disk and includes the I, H and A bands. Length change of the myocyte is accomplished by changes in the dimension of the sarcomere; A bands remain constant in length while the I and H bands change.

myofibrillar (adjective)

having to do with the myofibril

strand-like structure in myocyte.  Actin, myosin, titin and nebulin are myofilaments.  These myofilaments are the major proteins of the sarcomere.

growth and development of muscle tissue, including creation of new muscle fibres.

small molecules that are released from muscle cells and serve to regulate some function of the same cells or neighboring cells or other tissues within the body.

linking protein of the M-line of the sarcomere; at the middle of the A-band.

the cytoplasmic volume surrounding a myonucleus. Muscle cells are multinucleated and each nucleus controls the transcriptional activity for the surrounding territory.  The size of the myonuclear domain is calculated by dividing the cell volume by the number of nuclei.

the fluid and gel-like substance within the membrane of a muscle cell (myocyte) including dissolved and suspended substance, including the contractile proteins. 

a molecular motor. Skeletal muscle myosin (myosin II) is just one member of the superfamily of molecules called myosin. Myosin is the principle molecule accounting for the structure of the thick filaments of the sarcomere in a muscle fibre.  Each myosin molecule has a long alpha helical segment (two strands intertwined) and two heavy chains; one on the end of each strand. The portion of the myosin molecule that extends away from the thick filament is composed of the S1 and S2 segments. The S2 segment is a continuation of the alpha helix chain and the S1 segment is the portion of the molecule that interacts with actin. The S1 segment is also the heavy chain that has several isoforms that distinguish the fibre type of the myocyte. Each myosin S1 segment also has 2 light chains associated with it; a regulatory light chain and an essential light chain.

myosin ATPase

an ATPase is an enzyme with the capability to hydrolyze ATP, forming adenosine diphosphate and releasing energy from the high-energy phosphate bond. The energy released is typically used for biological work but also results in release of heat. Myosin ATPase is the molecular motor that splits ATP to ADP and uses the energy for motion or force development. In skeletal muscle, myosin ATPase reacts with actin to accomplish force generation and/or length change of the sarcomere.

myosin head

that portion of the myosin molecule that includes: actin binding site, ATP binding site, lever arm and light-chain binding sites.  The myosin head (also called the S1 segment) is a globular protein, attached to an alpha helix (S2 segment) that joins and helps form the thick filament.

myosin is a superfamily of motor molecules, typically composed of 2 heavy chains and 4 light chains. The heavy chain of myosin can be divided into different domains: head, neck, and tail. The head is the motor domain and the neck undergoes a lever action to accomplish motion. The regulatory light chains undergo phosphorylation to modulate the function of the motor domain. 

the enzyme that catalyzes the reaction resulting in the phosphorylation of the regulatory light chains of myosin.  MLCK is activated by binding of Ca²⁺ to calmodulin within the myocyte.  When [Ca²⁺] rises in association with contraction, this enzyme is turned on.

a low molecular weight molecule that can be phosphorylated by the enzyme, MLCK. Phosphorylation of RLC gives the myosin head increased mobility, allowing it to swing away from the thick filament backbone. This increased mobility contributes to an increased probability for the myosin head to bind to actin when Ca²⁺ is bound to troponin C. Phosphorylation of RLC is thought to result in increased Ca²⁺ sensitivity associated with prior activation: staircase, posttetanic potentiation, and postactivation potentiation.

Essential light chain: 

Each myosin head has two light chains attached; regulatory light chain and essential light chain. Without the essential light chain, isometric force is greatly reduced.

Myotrophic: 

the property that allows a chemical to have an influence on the maintenance and/or growth of a muscle.

a membrane receptor, also classified as an ionotropic receptor, that will bind glutamate, usually at a synapse in the central nervous system. The NMDA receptor is an ion channel that is activated by binding of glutamate.

Sodium channel.  A transmembrane protein that has a pore through which sodium can selectively move. Sodium will move down its electrochemical gradient. 

filamentous protein located in sarcomere of skeletal muscle in association with actin.

end of the axon, where synapse with a target tissue or subsequent neuron occurs.  An a motor neuron branches several times and each branch synapses with a muscle fibre, allowing activation of each muscle fibre innervated by that motor neuron.

a network of neurons in the central nervous system that provide repeated on and off activation, often associated with repeating functions like breathing.

improved ability to perform a task with resistance by improved activation of motor units.  Strength training on a regular basis (2-4 times per week) results in rapid improvement in the ability to perform the practiced movement with increasing weight. This early improvement in performance results from improved activation of the involved muscles: neural adaptation. Several factors contribute to this improved performance: 1) the ability to persistently activate high threshold motor units; 2) inhibition of antagonist muscles; 3) ability to activate motor units at higher frequency; 4) inhibition of Golgi tendon organ inhibition; and 5) use of the catch-like property of muscle activation (high frequency doublet at beginning of contraction).

a chemical, released from one neuron that can modulate the response of another, not necessarily at the synapse, but binding to a receptor and usually initiating a second messenger system that can have a prolonged effect on the sensitivity of the target neuron to subsequent excitatory or inhibitory influence.

nerves and muscles are activated by generation of an action potential that is propagated along the membranes of the respective tissue. 

the nerve terminal and end-plate region of the myocyte and the gap between these two constitute the neuromuscular junction.  Activation of the muscle fibre occurs at the neuromuscular junction when an action potential arrives at the nerve terminal and triggers the release of acetylcholine into the junctional gap.  Acetylcholine binds to its receptor on the end-plate membrane, opening channels that allow Na⁺ and K⁺ to move across the membrane.  This ion movement causes depolarization and triggers an action potential on the myocyte membrane.

neurolemma

the plasmalemma and basement membrane of a neuron.

the processes involved in transmission of a nerve signal (action potential) to a muscle cell signal. This sequence of events is summarized as the following: axon action potential arrives at nerve terminal; Ca²⁺ channels open, allowing a puff of local change in [Ca²⁺]; Ca²⁺ binds to special proteins at docked vesicles, triggering exocytosis; neurotransmitter acetylcholine is released into the synaptic cleft; acetylcholine binds to receptors in secondary synaptic clefts of muscle fibre end-plate region; Na⁺ and K⁺ permeability increases; end-plate depolarizes to threshold; Na⁺ channels open, propagating the action potential along the surface membrane of the muscle.

small molecule or amino acid that serves as a signaling molecule released from a nerve terminal and affecting the target cell (a neuron or other type of cell, like muscle or gland). Common neurotransmitters include acetylcholine, norepinephrine, dopamine, glutamine etc.

chemical signaling molecule, but also a free radical (has an unpaired electron). Created by NO synthase and has many effects within the body including smooth muscle relaxation leading to decreased vascular resistance. 

refers to nerve signals generated by pain or an unusual chemical or concentration of chemical in the body. 

energy metabolism; the formation of ATP without the use of oxygen. Non-aerobic metabolism includes the immediate and short-term energy systems: the immediate energy system includes net hydrolysis of adenosine triphosphate and creatine phosphate. The short-term energy system is glycolysis leading to the formation and accumulation of lactate.

any dietary substance that can be produced by the body and therefore does not need to be supplied by the diet.  

a hormone and neurotransmitter released from the adrenal medulla and from nerve terminals of the postganglionic sympathetic nervous system. Norepinephrine is a catecholamine.  

a protein that regulates development of many tissues including skeletal muscle. It activates transcriptional activity of genes important in muscle growth (e.g. IGF-1).

Is a transcription factor for a host of nuclear genes encoding mitochondrial proteins (NuGEMPs).

nuclear envelope: 

the fenestrated double membrane (two lipid bilayers) around the nucleus. Unlike the plasmalemma, the nuclear envelope has pores that make it quite permeable to transport of a number of small molecules. The outer lipid bilayer is continuous with endoplasmic reticulum where protein synthesis occurs.

abbreviation for ‘nuclear genes encoding mitochondrial proteins’. The mitochondrial genome encodes for 13 proteins. The remaining ~1487 proteins that constitute the mitochondrial proteome are encoded by nuclear genes.

matching nutritional caloric intake with energy expenditure over an extended period of time.

a disease state represented by substantially high amount of body fat, often associated with heart disease, diabetes and hypertension.  Obesity is diagnosed by a body mass index greater than 30, but a particularly muscular individual could be misdiagnosed by this method.

research that involves direct observation of the subject of interest in their natural environment, without interference.  This approach is often used in behavioural research; in an attempt to understand animal or human behaviour.

physical activity engaged in as part of an occupation.  Workplace physical activity.

the relationship between voltage (V), current (I) and resistance (R) is:  V=IR

This is analogous to the relationship between blood pressure (P), flow (Q) and vascular resistance (R): P=Q/R   

in an attempt to identify a lactate concentration that could be objectively identified as a lactate threshold, 4 mM blood lactate was identified as an important marker of substantial ongoing anaerobic glycolysis.  This concentration was selected because it was thought that this concentration in the muscle represented a concentration at which transport of lactate into the blood reached a maximal rate.  OBLA is identified by plotting blood lactate vs stage of the incremental test (power output, speed or heart rate).  One of the values of the objective selection of 4 mM is that it can be chosen between discrete power outputs or levels of the incremental test.

a process of identifying and binding bacteria and other foreign substances by phagocytes. 

the muscle length (or more specifically, sarcomere length) that allows the greatest isometric active force. Optimal length of a muscle depends on the length of the actin filaments, which is slightly different between species.  Frog muscle was studied at the single fibre level long before human muscle.  Frog thin filaments are 1 micrometer in length while human thin filaments are 1.3 micrometers. Myosin filament length is universally 1.6 mm. Optimal length occurs at a sarcomere length from 2 thin filament lengths to 2 thin filament lengths plus the length of the bare zone on the myosin filament.  In frog muscle, this is 2 – 2.2 micrometers. In human muscle, this is 2.6 to 2.8 micrometers.

a measure of the density of dissolved particles in a solution.  Osmolality is the total amount of solute particles in a given weight of solution.  In the body, the relevant solutes are primarily the electrolytes, proteins, and glucose.

a condition where bone mineral density is lower than normal, but not yet critical (osteoporosis). Wikipedia

a condition characterized by low bone mineral density. Bone mass is lost due to disease, diet, inadequate physical activity, or aging.  Low bone mineral density is a risk for fracture.  Wikipedia 

a measure of the density of particles in a solution, similar to osmolality, but here the particles are quantified per volume of solvent.  Units of osmolarity would be osmoles (or milliosmoles) per liter.

chemical reactions that use oxygen to transduce energy from one chemical form to another. Also known as aerobic metabolism or cellular respiration. The typical end product of oxidative metabolism is adenosine triphosphate (ATP), which is the universal form of chemical energy in the body. Heat, CO₂, and water are also products of oxidative metabolism. Oxidative metabolism is confined to the mitochondria in cells of the body and includes electron transfer chain and oxidative phosphorylation.  Wikipedia

the coupling of electron transfer with the f-complex of the mitochondria where ATP is synthesized is called oxidative phosphorylation.  The source of electrons is NADH and FADH₂.   NCBI

the waterfall-like decrease in partial pressure of O₂ from atmosphere to tissue.  Partial pressure of O₂ (mm Hg at sea level) is approximately: ambient, 150; alveolar, 100; arterial, 95;  capillary, 20-95; tissue, 2-30.  Values depend on the following factors: altitude, fraction inspired O₂, alveolar ventilation, ventilation-perfusion ratio, cardiac output, distribution of cardiac output, tissue capillary perfusion, shunts, and metabolic rate.

the difference between measured oxygen uptake and expected oxygen requirement. When intensity of exercise is below anaerobic threshold, oxygen uptake will reach a steady state within 2-4 min. If this steady state rate of oxygen uptake is assumed to be the oxygen required from the beginning of the exercise, then the oxygen deficit can be determined as the difference between measured oxygen uptake and this anticipated oxygen requirement. 

the relative occupation of Hb with oxygen. When you plot the % of Hb fully bound with O2, against the partial pressure of O2, you get the oxygen dissociation curve. This graph shows the saturation of Hb; as PO2 decreases, O2 dissociates from Hb in a sigmoid shaped relationship, decreasing slowly between 100 mmHg and 50 mm Hg, then more quickly between 50 mm Hg and 15 mm Hg.  The rate of  dissociation slows again below 15 mm Hg.

a measure of the rate of use of oxygen in the body, or part of the body. This is often measured across the pulmonary system as the difference between the O₂ taken in and the O₂ expelled in a fixed amount of time.  

in cardiovascular physiology, a natural pacemaker is a collection of cells that spontaneously depolarize, triggering the beat of the heart. These cells are typically found in the dorsal aspect of the right atrial wall.  A pacemaker can also be an electrical device that rhythmically activates the heart. implanted under the skin and electrically attached to the heart with wires threaded to the heart via a vein.

pacemaker driven oscillator

a collection of neurons that spontaneously depolarize to threshold, activating a response that results in a regular behaviour, like breathing.   

swelling of the optic disc due to increased cranial pressure.  The swelling can be seen with an ophthalmoscope.  The free dictionary

when muscle fibres are organized into bundles that lie in parallel with the line of action of the muscle. 

a part of the autonomic nervous system that regulates the gastrointestinal system and the cardiovascular system, without voluntary input. In many cases, the parasympathetic nervous system is opposed by the sympathetic nervous system. Wikipedia

a secondary physical activity readiness questionnaire to be filled out by a physician when a patient has indicated a desire to engage in more challenging physical activity than they have recently engaged in.  The PAR-MED-X needs to be presented to a fitness professional when the client or patient has provided a positive response to any question on the PAR-Q. 

physical activity readiness questionnaire.  The Canadian Society for Exercise Physiology promoted the use of this standardized questionnaire to determine if a change in exercise habits could be undertaken without negative medical implications.  This questionnaire has often been used as a screening device for the involvement of subjects in exercise related research.  The PAR-Q has recently been replaced by the “Get Active” questionnaire.

that portion of the total pressure exerted by a given gas. For example, if the barometric pressure is 760 mm Hg, and O₂ is .209 of the total gas in the atmosphere, the partial pressure of O₂ in the inspired air is 0.209 ´ 760 = 158.8 mm Hg. Gas partial pressures also apply to dissolved gas in body fluids. Typical values for partial pressure of O₂ (PO₂) in arterial and venous blood are 95 mmHg and 50 mm Hg respectively.   Wikipedia

PO₂                                                    PaO2                                               PvO2

partial pressure of oxygen          partial pressure of arterial oxygen          partial pressure of venous oxygen

PCO₂                                                   PaCO2                                                PvCO2

partial pressure of carbon dioxide      arterial                                                       venous

PIO2                                             PEO₂                                              P_ETCO₂

_{partial pressure of inspired oxygen               expired oxygen                                                        end tidal} 

a Canadian program that promotes a physically active lifestyle.  participaction

a calcium-binding protein typically present in type IIb muscle fibres. Parvalbumin accelerates relaxation of fast-twitch muscle of small animals by binding calcium, thereby decreasing the amount of calcium available to bind to troponin.

the force with which a muscle resists stretch without activation of the muscle. Within the normal range of lengths of most muscles of the human body, passive force is quite low. However, certain pathological conditions will result in higher passive forces, limiting the range of motion.

a chemical pattern associated with a pathogen that can be recognized by defense units within the invaded organism. These chemical patterns are often associated with glycans or surface molecules of the microorganism.

a substance or organism that can cause disease.  Usually an infectious microorganism.  Wikipedia

molecular receptors that recognize certain chemical sequences of invading pathogens. These receptors are typically associated with macrophages and monocytes.       Wikipedia

negative log of the concentration of calcium. Similar to pH (negative log of [H⁺]). pCa²⁺

the highest mass of skeletal bone mass achieved over a lifetime. Bone mass increases as we grow and also responds to any activity that puts stress on the bone, usually increasing in density and strength in response to such stress. Inactivity and lack of stress reduces bone mass. Peak bone mass is achieved in early adulthood, after which bone mass decreases as we age.

the highest rate of oxygen uptake achieved in an incremental exercise test.  This is often used rather than maximal oxygen uptake if the criteria for reaching maximal oxygen uptake have not been confirmed.

when muscle fibres are oriented at an angle to the line of action of a muscle-tendon unit.  Pennate derives from the term “penne” like a feather.

thick layer of connective tissue that divides the muscle into fascicles.

intermittent breathing, with typically a period of apnea followed by hyperpnea.  When we breathe, we normally tend to breathe with a regular pattern; at rest this is about 10-15 breaths per min.  Periodic breathing presents with a lack of breathing or low frequency breathing, followed by a brief period of compensatory high frequency breathing.

peripheral refers to non-central. Central is either central nervous system or central processes like ventilation and circulation. Peripheral factors typically occur in the active muscles, contributing to regulation of central processes.

within the cardiovascular system, peripheral refers to small arteries, arterioles, capillaries, venules and small veins.  In contrast, central refers to the heart, large arteries and large veins.

all neural tissue outside the brain and spinal cord.  Also referred to as systemic neural tissue.

slowly inactivating Na+ and Ca2+ ion channels that are regulated by voltage allow movement of Na+ and Ca2+ into the cell, slowly depolarizing it. PIC allows modification of the gain (sensitivity) of spinal motor neurons.

peroxisome proliferator-activated receptor-gamma coactivator (PGC-)1 alpha is a protein that is the master regulator of mitochondrial biogenesis. It plays a central role in regulating energy metabolism. PGC-1α facilitates the transcription of proteins that transcribe nuclear encoded mitochondrial proteins (NuGEMPs).

the negative log of the hydrogen concentration. Wikipedia

a cell of the body with the capability to take up debris from the interstitial space by endocytosis. 

a phosphorylated creatine molecule, which serves as an energy intermediate. Phosphocreatine can transfer the phosphate group to ADP, thereby reforming ATP. The enzyme that catalyzes this reaction is creatine kinase. Wikipedia

to add a phosphate group to a molecule.  Phosphorylation of an enzyme will typically control the enzyme activity, either turning it on or off.

when a phosphate group has been added to a molecule the reaction is called phosphorylation reaction.  This reaction is typically catalyzed by a kinase.  Phosphorylation is used in signaling cascades to activate or inhibit enzymatic processes.