Glossary Terms: phys to tend

Gas dissolved in a fluid (like blood) will exert a partial pressure in equilibrium with the atmosphere that fluid is exposed to (in the lungs).  Partial pressure of carbon dioxide in the mixed venous blood, which is in the pulmonary arteries is 45-65 mmHg at rest and during moderate to vigorous exercise.  At higher intensities, the PCO₂ can rise higher, but hyperventilation prevents arterial PCO from rising too much.  Although CO₂ is more soluble in plasma than O₂ is, dissolved CO₂ represents only a portion of the total CO₂ transported in the blood.

bodily movement resulting from activation of skeletal muscles and requiring energy input.

classes, embedded in the curriculum, designed to educate the student in physical literacy and to engage in regular physical activity.

dead space in the pulmonary system is considered volume where gas exchange does not occur. This dead space can be anatomical, in the airways where gas exchange is not expected to occur, but can also be alveolar space where circulation is inadequate to allow gas exchange. Physiologic dead space includes anatomical and alveolar spaces where gas exchange does not occur. 

chemical compounds found naturally in plant foods that can influence health. Wikipedia

a term describing the structure of a muscle, based on the orientation of the muscle fibres; when muscle fibres are oriented at an angle to the line of action of a muscle-tendon unit, it is called a pinnate or pennate muscle. 

white blood cells, lymphocytes, that secrete antibodies, performing an important function in the immune response of the body.  White blood cells are formed in bone marrow.  Wikipedia

also plasmalemma; the lipid bilayer that separates intracellular from extracellular space; surrounds individual cells.  The plasmalemma contains several proteins including ion channels and pumps as well as hormone receptors and enzymes.

tissue is considered to have plasticity if it can alter structure and function to accommodate different environmental and functional demands. Most tissues of the body have plasticity, but skeletal muscle demonstrates a broad range of adaptations to environmental and functional demands because it has considerable plasticity.

the fluid pressure within the pleural space.  The pleurae line the chest wall and envelope the lungs. This space is fluid-filled and typically has a pressure less than atmospheric pressure.

having a charge separation or charge difference between sides or ends. A cell membrane that is polarized has a difference in change between sides of the membrane. For example, nerve an muscle cells typically have more negative charge inside than outside the cell. This difference is about -85 mV at rest.

a high number of red blood cells. This will usually result in a high haematocrit, a dangerous situation due to increased viscosity of the blood.

three of the 5 types of white blood cells are polymorphonuclear leukocytes, including the lymphocytes.  The other two are eosinophils and basophils.  The nuclei are lobular, looking like they are going to divide or have multiple nuclei (polymorphonuclear).

a form of activity dependent potentiation; enhanced contractile response for a given activation resulting from immediately prior voluntary activation.  The “given activation” can only be known for certain when electrical or magnetic stimulation is used to activate the muscle of interest.

improved performance resulting from performance of a high effort voluntary contraction or sequence of contractions. 

referring to the period of time immediately following a meal. Wikipedia

describing the structure or function that is the target of synaptic transmission. 

postsynaptic membrane

the plasmalemma of the target tissue. This could be an organ, muscle, fat or neuron. The postsynaptic membrane will have specific receptor molecules that will bind the neurotransmitter released from the presynaptic membrane.

a form of activity dependent potentiation; enhanced contractile response for a given activation resulting from immediately prior tetanic stimulation.

a transporter protein, embedded in the membrane of neurons that transports potassium and chloride out of the cell. This transporter is a symport, carrying both ions in the same direction. Energy for operation of this pump comes from the concentration gradient for potassium.  

the rate of energy transfer. Often used to refer to mechanical power, which is the rate of doing mechanical work. Units of power are watts (J×s^-1). Can also refer to metabolic power, or rate of energy use in a muscle or in the body. Synonym, work rate.

the reconfiguration of the myosin head in response to binding to actin. This reconfiguration results in force generation and if the resistance to shortening is low enough, motion will result.

the relationship between power output and velocity of shortening of a muscle (or angular velocity of joint rotation).  This relationship has an optimal velocity where power output is greatest and decreases to zero at zero velocity and at maximal velocity.

in contrast with afterload, the preload is the load imposed on the muscle immediately prior to activation. The preload will dictate the initial length of the muscle according to the passive force-length relationship.

premature ventricular contraction

a contraction of the ventricles, initiated prior to the time a normal beat was expected; usually due to spontaneous depolarization of a cell within the ventricle

a continuously increasing work of the locomotor muscles, such as, during a ramp protocol maximal exercise test.  

a value representing the slope of a relationship; also the proportion that one variable changes for each unitary change in the other variable. Wikipedia

research conducted by planned recruitment of subjects from a defined population with prescribed measurements conducted.  In contrast, some research relies on observation of already collected information or recall of things like physical activity.

chains of amino acids linked together by peptide bonds and configured into a three-dimensional structure. This chain of amino acids will have a three-dimensional structure with a specific function in the body. Proteins are important molecules in the body serving the following functions: receptors, enzymes, signaling molecules, pumps and transport molecules, as well as binding and structural functions.  Protein provides energy when metabolized (4 kcal×g^-1). 

the production of new proteins through the process of translation where mRNA serves as a template and tRNA brings amino acids for joining to the growing strand.

a protein that has several glycosyl units attached.  These proteins make up much of the intercellular matrix, binding to other constituents of the connective tissue.  Proteoglycans are also an important component of cartilage.

a state of well-being from the perspective of the mind.  Also, mental health.

the amount of air flowing in and out of the lungs every minute.  

the maturation process described by the transition to adulthood and development of the capability of sexual reproduction. 

the oxygen and carbon dioxide gas exchange that occurs between the blood contained within the pulmonary capillary and the air within the lungs.

the pressure difference between systolic and diastolic pressures.

acronym for “physical work capacity at a heart rate of 170 beats per min”. From the relationship between power output on a cycle ergometer and heart rate achieved at each stage of an incremental test, the power output that would be achieved at a heart rate of 170 beats × min^-1 can be estimated.  The PWC₁₇₀ is a sensitive indicator of cardiovascular health.

blood flow; usually cardiac output

electromagnetic, light, or heat waves. In the case of radiated heat, there can be a heat transfer from one body to another without warming the intervening substance (air or water).  

radiative (adjective):

referring to the emission of heat in the form of radiated energy

in this type of study, the participants are randomly allocated (e.g. a name drawn out of a hat) into a control group and one or more experimental group.

activation of the motor nerves and corresponding muscle fibres at a given frequency.  Rate coding can affect the force of muscle contraction according to the force-frequency relationship of each motor unit.

recruitment

the activation of skeletal muscle motor unit when increasing force or power output. Recruitment is the increase in number of active motor units.

a method to allow comparison across a broad range of subjects by normalizing a variable by some standard of comparison.  For example, resting oxygen uptake is divided by body mass to allow comparison across individuals of varying body mass.  The ratio standard, to be useful, must reduce the variability in a meaningful way.

are molecules that contain oxygen and easily react with DNA, RNA, and proteins within the cell. This reaction modifies the structure or function of these molecules and often leads to damage. Examples of ROS are hydrogen peroxide, hydroxyl radical, and superoxide anion.

a protein molecule that recognizes and binds a very specific signaling molecule in the body.  A receptor is commonly located in the membrane of a cell and when bound to the signaling ligand alters some property of the cell.  Often this alteration is activation of an enzyme or opening of a channel.  Receptors can also be intracellular.

alpha receptor

a catecholamine receptor that binds norepinephrine with high affinity and epinephrine with less affinity

beta receptor

a catecholamine receptor that binds epinephrine with high affinity and norepinephrine with less affinity

neural control of agonist-antagonist pairs of muscles.  Neural circuits that facilitate inhibition of the antagonist when the agonist is activated.  

disynaptic reciprocal innervation

when the inhibition of the antagonist occurs by a neural pathway involving just two synapsis.

the amount of a nutrient that is sufficient to meet the single day nutritional requirements of 97-98 % of healthy individuals. Wikipedia

the amount of specific nutrients required in the diet, based on the amount required by 97 % of healthy adults. Wikipedia

return to homeostasis after an event that disturbs the normal resting state of an organ or the entire body.

duplication or copying of a substance or process. Control systems in the body are considered redundant when more than one system can control the same variable. This is considered a valuable redundancy.  

the absolute refractory period is the time during and immediately following an action potential when the neuron cannot be activated a subsequent time. The absolute refractory period lasts as long as the inactivation gate of the fast sodium channel is closed.  The relative refractory period represents a time immediately following the absolute refractory period when a subsequent action potential can be elicited but this activation requires more than the usual current or depolarization.  The reason for the relative refractory period is afterhyperpolarization.

the process of generating new tissue

an effector system that can be altered to allow control of some variable of the physiological system.  For example, a control system can regulate heart rate to control blood pressure.

a low molecular weight molecule, attached to the S1 segment of myosin, 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.

ingesting fluid to replace fluids lost from the body.  Rehydration is important after exercise in the heat or particularly prolonged exercise during which fluid intake has not kept up with fluid loss. 

expression of intensity of exercise relative to a standard, like maximal oxygen uptake, maximal heart rate, or anaerobic threshold. In contrast, absolute intensity relates to some measure of intensity, like speed or power output. Exercise can be prescribed by describing the intensity, and in many cases a relative intensity is more appropriate than an absolute intensity. Another form of relative intensity is relative to some threshold measure (related to anaerobic threshold). For example, you may want to exercise at 80 % of the intensity at ventilatory compensation point.

When a charge separation has been reduced then returned to the original value, it will be considered to have undergone depolarization and repolarization. Wikipedia

the process of investigating a theory or hypothesis.  Research takes the form of making measurements under circumstances that allow you to make inference about some theory for how things work.  Often this will require an intervention with measurements to quantify the impact of the intervention on some outcome.

the amount of air that remains in the lung after maximal expiration.

can have several meanings:

vascular resistance

impediment to flow of air or fluid (blood). Resistance is proportional to radius (squared) and to length of a tube. Resistance can be quantified by change in pressure divided by flow.

electrical resistance

impediment to flow of electric current; 

resistance training

repetitive motions with effort, slowed by loading. The goal of resistance training is to maintain or increase muscular strength. Resistance training has specificity; the training response occurs specifically for the muscles trained and specifically for the type of activity undertaken. Wikipedia

a change in [H⁺] due to ventilation. Ventilation removes CO₂ from the body and when more CO₂ is removed than is produced by metabolism, this removal results in decreased [H⁺] (alkalosis) because of the following reaction is driven to the right: HCO₃ + H⁺   ®  H₂O + CO₂

increased [H+] due to inadequate removal of H⁺ or increased production of H⁺ will result in respiratory acidosis.

respiratory acidosis

an increase in [H⁺] due to ventilation or metabolic production of CO₂. Impaired or inadequate ventilation will increase partial pressure of CO_2, resulting in formation of carbonic acid which dissociates into H⁺ and bicarbonate.

The respiratory centre is composed of 4 groups of a nuclei in the medulla oblongata and pons regions us of cell bodies in the central nervous system that regulate ventilation.

caudal ventral respiratory group (cVRG)

part of the ventral respiratory group, situated caudally (towards the rump or tail) in the medulla.

dorsal respiratory group (DRG)

neurons of the DRG initiate inspiration, so are responsible for the rate of breathing; located in the medulla

ventral respiratory group (VRG)

this group of neurons are responsible for regulating expiration, which is normally a passive process, but becomes active during exercise when the rate of ventilation is increased. Located in the mudulla.

pontine respiratory group

includes the pneumotaxic (regulates termination of inspiration); input to the VRG;  and apneustic areas, triggers sustained inspiration; input to the DRG.  Located in the pons.

the ratio of whole body VCO₂ and VO_2, measured at the pulmonary system_. This ratio is primarily affected by metabolism and is used to estimate RQ. RER should be equal to the RQ when total O₂ and CO₂ stores in the body are not changing. When these stores are not changing, the pulmonary exchange of O² and CO² will reflect the metabolic use of O² and production of CO².  The RQ is used to estimate the proportion of fats and carbohydrates metabolized. Wikipedia

water vapour added to the air we breathe in is lost with each breath.  This fluid loss is called insensitive fluid loss because we are unaware of this water leaving the body.  The magnitude of respiratory fluid loss is dependent on ambient conditions like the temperature and relative humidity of the air we breathe and also on the magnitude of the minute ventilation.

the ratio of the metabolic production of CO₂ to the metabolic use of O₂.  This ratio will be between 0.7 and 1.0.  The RQ for fats is 0.7.  The RQ for carbohydrates is 1.0.  The RQ for protein is about 0.85.  When all three are metabolized, the RQ will be influenced by the proportion of each of these.  For simplicity, we typically assume the contribution from protein is negligible and therefore the RQ can be used to estimate the proportion of fats and carbohydrates metabolized.

an arrhythmia is an event that disrupts the regular beating of the heart. Respiratory sinus arrhythmia is a normal variation of the heart rate that oscillates with ventilation.  The normal rate of beating of the heart originates in special pace-maker cells in the sinus (back of the right atrium). Heart rate typically will increase during inspiration and decrease during expiration. 

the pulmonary system is divided into zones based on either a two-part system including the anatomical dead space vs other or into three vertical zones (upper, middle and lower) which correspond to low, moderate and high perfusion areas of the lungs; this latter system is based on an upright body where perfusion of the lungs is affected by gravity.

the amount of energy needed to meet energy demands of the body while at rest. To measure resting metabolic rate, the person who is being measured should be sitting or lying down. Resting metabolic rate is more variable than basal metabolic rate due to effects of recent food consumption or prior physical activity.  Wikipedia

a fibrous band of connective tissue that constrains tendons close to the bone. When the tendon is held close to the bone (primarily at the wrist and ankle), the moment arm is kept short; this decreases the potential moment generated by the muscle contraction but increases the angular displacement and angular velocity for a given linear length change or velocity of shortening respectively. 

a collection of cell nuclei that are sensitive to O₂ and H^₊. These are the central chemoreceptors that are responsible for controlling cardiovascular and ventilatory responses of the body.

the minimum current amplitude of potentially infinite duration that will elicit an action potential by bringing the membrane to threshold.

a polymer of nucleic acids, coding proteins; 3 nucleic acids represent each amino acid.  RNA is transcribed from DNA in the process of protein synthesis.  Forms of RNA include: messenger RNA, transfer RNA and ribosomal RNA.

cellular organelle or particle usually associated with endoplasmic reticulum that functions in protein synthesis. Ribosomes are particles containing transfer RNA and amino acids engaged in protein synthesis.  Wikipedia

a measurable variable that provides some predictability for a medical condition.  For example, increased body fat composition is related to metabolic syndrome and type II diabetes.  Epidemiologists use statistical procedures to identify correlated observations that lead to identification of risk factors for a given disease.  Wikipedia

  a group of neurons in the rostral portion of the medulla that participate in regulation of ventilation.

a large protein embedded in the membrane of the terminal cisternae, facing the transverse tubule; functions as a Ca²⁺ channel, allowing Ca²⁺ to move out of the sarcoplasmic reticulum into the cytoplasm to activate contraction.

the globular head of the myosin molecule, containing sites for actin and ATP binding/hydrolysis. The regulatory and essential light chains of myosin are attached to the S1 segment of myosin.

protein involved in activating translation by catalyzing a phosphorylation reaction. Like all kinase enzymes, this activation is achieved by phosphorylation of the target protein.

when motor unit stimulation results in incompletely fused tetanic contraction, the oscillations in force reach a peak early in the repetitions and later there is a decrease in peak values.  This drop of force, or sag, is recognized as a property of type II motor units.  Type I motor units will not demonstrate sag; oscillation of force during an incompletely fused tetanic contraction do not decrease over time.

a Ca²⁺ pump that transfers cytoplasmic Ca²⁺ into the organelle known as sarcoplasmic reticulum or endoplasmic reticulum, using adenosine triphosphate (ATP) for the energy needed to transport against the concentration gradient. In skeletal muscle, Ca²⁺ is sequestered in the sarcoplasmic reticulum to a concentration of about 1.5 mM, reducing cytoplasmic concentration to about 70 nM. Wikipedia

plasmalemma and basement membrane of the muscle cell.  The plasmalemma is a lipid bilayer with phospholipids and cholesterol embedded in it as well as a variety of proteins: ion channels, ion pumps, receptors and enzymes. 

the smallest functional contractile unit of a muscle. The sarcomere extends from one z-disk of a myofibril (or across the entire cell) to the next. Each myofibril has sarcomeres in series from one end of the cell to the other. The major proteins of the sarcomere include actin, myosin, titin, nebulin, and intermediate filaments (desmin, synemin, and vimentin). Troponin and tropomyosin are associated with the thin filaments while myomesin forms struts between the thick filaments.

an intracellular tubular structure with its own membrane that sequesters calcium, making it available for release when the myocyte is activated.  Sarcoplasmic reticulum has several specialized proteins including Ca²⁺-ATPase or calcium pump, Ryanodine receptor or calcium release channel and calsequestrin, a protein that binds calcium within the sarcoplasmic reticulum.

quiescent precursor muscle cells. They contain a single nucleus and are located between the sarcolemma and basal lamina that surround a myofibre. Satellite cells fuse together to form terminally differentiated myofibres that are multinucleated. They can also fuse with existing fibres to donate healthy myonuclei. 

specialized cell of the afferent nervous system that is designed to detect some modality in the body. Sensor cells can detect pressure, touch, odour, pain, taste, light, sound, muscle length, and force.

when the value of a variable is regulated by a control system, the value it is regulated close to is the set-point. For example, when the set point of the temperature is 21°C, the thermostat will regulate heating and cooling to keep the temperature close to 21°C. Wikipedia

a vascular connection that bypasses the capillary circulation.  In the systemic circulation, this would be a connection from arteries or arterioles to venules or veins (left to right shunt in the heart).  In the pulmonary system, this would be from pulmonary arteries or arterioles to pulmonary venules or veins (right to left shunt in the heart). verb, to move blood from arterial to venous circulation or the opposite without passing through capillaries is to shunt the blood.

the shape of a relationship that begins with a plateau of low values for the dependent and independent variables, but then the values of the dependent variable increase dramatically over a narrow range of values for the independent variable, before leveling off at another plateau. A sigmoid relationship can be mathematically described by a Boltzman equation. Wikipedia

a sequence of reactions that occur in response to a specific event or change in the environment and lead to a subsequent change in synthesis of a molecule or activation of a process.  Signaling pathways may rely on change in enzyme activities or ion concentrations. 

When the means of measurement of a variable on two different populations are different by a magnitude that you  are confident that 95 times out of 100, the mean would be different (in the same direction), then the difference is called significant.  This means that the variability and number of measurements is enough to give you confidence in the difference.

an irregular heart beat that still originates at the sinoatrial (SA) node.  

ventilatory sinus arrhythmia

an irregular heart beat due to ventilatory effect on SA node

Contractile tissue under voluntary control for the purpose of force generation or motion.  Skeletal muscles are typically involved in movement of the body parts by attachment to bones by tendon.  Skeletal muscles are responsible not only for locomotion, manipulation and force generation, but also breathing, vocalization, directional vision and facial expressions.  Skeletal muscles have a unique banded pattern or striation, similar to cardiac muscle at the microscopic level, resulting in these muscles also being categorized as striated muscle.

the precise measurement of the thickness of a pinch of skin (and subcutaneous fat).  Skinfolds are measured with specific calipers designed for the purpose.  Skinfold measurements are used to estimate total body fat content, based on regression equations established with a large number of subjects using alternative ways to quantify body composition (underwater weighing, DEXA or magnetic resonance imaging).

a preparation to study contractile properties of muscle by regulation of the internal environment. This is achieved by chemical or mechanical destruction of the muscle membrane and immersion in a solution with the chemical make-up under study.  

the theory that explains how muscle length change is achieved.  This theory states that muscle length change is achieved by sliding of thin (actin) filaments past the interdigitating thick (myosin) filaments within each sarcomere of the myocyte. This theory does not explain how muscle contraction is achieved (see cross-bridge theory).

the amount of oxygen taken in and used in metabolism during exercise in excess of the rate achieved by three min. Normally, a steady state of oxygen uptake will be reached within 3 min when the intensity is below the anaerobic threshold. When the intensity is approaching or above the anaerobic threshold and exercise can be sustained beyond 3 min, oxygen uptake will continue to increase (often to maximal oxygen uptake if the intensity is high enough) beyond the time when a steady state should have been achieved.  It has historically been thought that this increase in VO2 represents an increased energy cost but recent work argues against this. In fact, this slow increase in VO2 may be related to recruitment of fast-twitch motor units which have been shown to have a slow time-constant for the rise in VO2.

a fibre-type classification that identifies skeletal muscle cells with type I myosin ATPase.  The contractile response of type I fibres is slow; it takes more time to reach the peak of a twitch contraction and the maximal velocity of shortening is slow compared to type II fibres.

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. Na⁺-K⁺ ATPase is a membrane transporter that uses the energy from ATP hydrolysis to transport 3 Na⁺ outward and 2 K⁺ inward, simultaneously across the membrane of muscle and nerve. This transporter helps to maintain the resting membrane potential of these cells. Wikipedia

Fast Na+ channel: 

an ion channel that selectively allows sodium to flow down it's electrochemical gradient into the cell. The fast sodium channel is activated by depolarization to ~-50 mV and closes when membrane potential reaches +30 mV.

Fast K+ channel: 

a transmembrane protein that is voltage activated and allows K+ to travel down it's electrochemical gradient. The pore of this channel is opened by depolarization to -50 mV and closure is achieved slowly as repolarization occurs.

body of the cell. This term is typically used in reference to neurons which are comprised of dendrites, cell body and axon.  The cell body is the location of the nucleus and where protein synthesis occurs.

a cytokine that promotes cell maturation and growth. Also known as growth hormone. Somatotropin is secreted from the anterior pituitary gland, in response to releasing factor from the hypothalamus. Wikipedia

measurement of a distance by emitting and detecting ultrasound.  The distance is estimated by measurement of the time for ultrasound to travel from one piezoelectric crystal to the other, knowing the speed of transmission in the medium of interest (often, this is skeletal or cardiac muscle).

also, length constant; the distance that a graded electrical potential can move passively along a dendrite, contributing to spatial summation.

spontaneous or stretch-induced activation of skeletal muscle. Involuntary contractions that impair mobility and contribute to muscle stiffness, but only while the muscle is active.  Spasticity is usually due to attenuated inhibition of motor pathways or more specifically, the motor neuron. 

spatial refers to an area. summation is the process of depolarization, leading to the threshold where an action potential will be generated. spatial summation is the impact of adding depolarizations from several nerve endings distributed over an area on the cell body that all simultaneously contribute to depolarization to threshold.

When stimulated with constant current input, more than sufficient to initiate firing of action potentials, a neuron will decrease the frequency of generation of action potentials. This is an adaptation that decreases the response to the same current.

an automatic response to sensory input that relies only on connections in the spinal cord; for example, input from a stretch receptor will synapse with alpha motor neurons of the same muscle, activating a contraction.

a device for measurement of pulmonary volumes including tidal volume, vital capacity and inspiratory and expiratory capacities

referring to the spleen. For example, splanchnic blood flow is the blood flow through the spleen. 

a beverage that has added electrolytes and/or carbohydrates designed to assist in rehydration during and/or following exercise that has resulted in sweat loss.  Gatorade and Powerade are two examples.  Wikipedia

a form of activity dependent potentiation that relies on enhancement of contractile force for a given activation during repeated submaximal contractions. Staircase potentiation is typically observed during repeated twitch contractions when the interval between these contractions is up to 5 s. Staircase can also result from repeated incompletely fused tetanic contractions.

a measure of the dispersion of values among subjects for a measurement that has been taken: sd = square root of the variance 

a measure of the dispersion of values among subjects for a measurement that has been taken. The standard error of the mean is an indication of how precise the mean value is as an estimate of the population mean.  Standard error = standard deviation / (square root of n). 

the condition where the internal environment (see internal milieu) remains constant with respect to volume and composition of the fluids (ions, substrates, and metabolic by-products).  

stiffness

the resistance to stretch or elongation. Quantified by measuring the length change per unit of force applied. Standardized stiffness is relative length change for a unit of force.

the highest force that can be exerted. Typically, strength is measured with isometric contractions, though slow dynamic contractions are also used. Wikipedia

stretch shortening cycle (SSC)

When muscle fascicle shortening is preceded by active stretch (lengthening. contraction), the force capability is enhanced, relative to maximal isometric contraction. The SSC is relevant in many ballistic movements, throwing, jumping etc. 

skeletal and cardiac muscles are striated; they appear banded (light bands corresponding to thin filaments and dark bands corresponding to thick filaments) under the microscope due to the repeating sarcomere structure that makes up the myofibril. The striations persist across myofibrils and between cells as well because the Z-disks are aligned.

brain vascular infarct or cerebrovascular accident. There are two major types of stroke: hemorrhagic stroke where a blood vessel is disrupted resulting in bleeding in the brain or constriction or blocking of a blood vessel resulting in impaired blood flow to a part of the brain. In both cases, brain tissue is destroyed and cerebral function is lost. Wikipedia

the volume of blood ejected from the heart with each beat. Wikipedia

the state of cross-bridge formation that represents the force generating state.  On activation, the myosin head can initially bind in a weak-bound state, but this transitions very quickly to a strong-bound state with motion of the lever arm portion of the myosin head.  Complete hydrolysis of ATP to ADP and inorganic phosphate is associated with the transition to the strong-binding state.

the pH of a fluid or the [H⁺] is dependent on the balance of positive and negative ions in solution.  Normally, positive ions outnumber negative ions.  

SID = [strong cations] – [strong anions] = [Na⁺ + K⁺ + Ca²⁺ + Mg²⁺] – [Cl^- + lactate^-]

An imbalance favouring negative ions will increase [H⁺] while an imbalance favouring positive ions will decrease [H⁺].   

below the maximal value; in reference to exercise intensity, this refers to an intensity of exercise less than that which will elicit maximal oxygen uptake.  

related to or lying just under the sarcolemma. The term ‘subsarcolemmal’ is often used to describe a population of mitochondria that are located between he sarcolemma and the myofibrils.

molecules that can undergo reaction to form a different molecule. For example, metabolic substrate would be fat, carbohydrate or amino acids that can be metabolized resulting in the formation of ATP with byproducts CO₂ and H₂O.  

substrate mobilization

the transfer of substrates for metabolism (primarily fats and carbohydrates) from sites of storage to the blood where they can be distributed to the tissues in need of these molecules. 

an intensity of exercise greater than that which will elicit maximal oxygen uptake.  

the mechanical adding of force from sequential activations when the interval between those activations is short enough that force begins to rise again before complete relaxation.  Summation results in tetanic contraction and contributes to the force-frequency relationship. 

spatial summation

the soma of a neutron will receive input from a number of sources and when several sources provide input at the same time but at different locations on the soma membrane, the resulting change in that soma will be cumulative.

temporal summation

When a soma receives repeated input from a given contact, the result will accumulate with the possibility of reaching threshold is the rate of input is sufficient to bring the membrane to threshold

fluid secreted in response to heat or stress, by special glands in the skin. Wikipedia

sweat rate

the amount (volume) of sweat that an individual excretes in a fixed amount of time

that portion of the autonomic nervous system that responds during stress (physical or emotional). The sympathetic nervous system increases heart rate, increases cardiac contractility, mobilizes substrate for metabolism, and constricts blood vessels through-out the body. Wikipedia

sympatholysis

the loss of effectiveness of the sympathetic nervous system. This is often used to describe the impact (or lack thereof) of the sympathetic nervous system on active muscle blood flow. Decreased vascular resistance prevails when the tissue requires increased blood flow.

the gap between nerve ending and target cell. Neurotransmitter is released from the nerve terminal membrane and crosses the synaptic cleft to reach the receptors on the target cell membrane.

synapse

the structural assembly that transmits a neural signal from the nerve terminal to the target tissue. The synapse includes the nerve terminal, the synaptic cleft and the region of the target tissue that lies adjacent to the nerve terminal.

secondary synaptic cleft (SSC)

infolding of the myocyte membrane under the nerve tertminus. The membrane in this folded section of the sarcolemma contain a high density of acetylcholine receptors.

ability of the synapse to modify itself to accommodate change in use. Plasticity involves protein degradation and new protein synthesis to adapt to increased or decreased use.

synaptic weight

the magnitude of influence that one nerve or node of neurons can have on another. Synaptic weight is proportional to the number of connections via synapse.

axodendritic synapse

when the nerve terminal ends on a dendrite

axosomatic synapse

when the nerve terminal ends on the soma of a subsequent neuron

an intermediate filament associated with the Z-disks and costameres of skeletal and cardiac muscle.

temporary loss of consciousness, passing out or fainting.  This loss of consciousness is typically due to decreased or absent blood flow to the brain

a review of the literature, following a stated and formulaic pattern.  In a systematic review, the method of searching the literature is stated and typically includes search terms and bibliographic databases included.  The total list of “hits” are culled by removing duplicates and further evaluation to remove articles that do not qualify according to specified inclusion criteria.  Wikipedia

the peak blood pressure achieved in the arterial system during a cardiac cycle. Blood pressure is the pressure exerted by the blood in the vascular system in a lateral direction (perpendicular to the vessel walls). When blood pressure is measured, two numbers are given. Systolic pressure is the high number and diastolic pressure is the low number.  

literally, this means a high heart rate, but should be interpreted as a higher than expected heart rate.  A resting heart rate greater than 100 beatsmin^-1 is considered tachycardia.  A heart rate higher than this during exercise is not considered tachycardia.

a high rate of breathing.  Normal rate of breathing for adults is about 10-20 breaths per min.  More than 20 breaths per min at rest would be considered tachypnea.  Tachypneic breathing is usually shallow (small tidal volume).  During exercise the breathing rate can increase to over 50 breaths per min.  Humans do not normally pant, but this pattern of breathing would be considered tachypnea.

composed of connective tissue; primarily collagen with small amounts of elastin and proteoglycans.  Tendons connect skeletal muscles to bone, and in most cases, there is tendon at both ends of a skeletal muscle.

tendon compliance

how easy it is to extend (elongate) a tendon. The inverse of stiffness.  Compliance is usually expressed as an elongation for an applied force.  

tendon stiffness

the ability of the tendon to withstand stretch when a force is applied.  Tendon stiffness is measured by quantifying the length change when a force is applied to the tendon, usually by activation of the muscle(s) attached to that tendon.  Stiffness is expressed as a force per unit of elongation; the inverse of compliance.