Glossary Terms: dead space to graph

the volume of air in the pulmonary system where gas exchange does not occur.  There are two overlapping concepts of dead space; anatomical dead space and physiological dead space.  Anatomical dead space includes the airways where gas exchange is not expected to take place, including upper airways, trachea, bronchi and bronchioles.  Physiological dead space includes the above and any respiratory bronchioles or alveoli where gas exchange is impaired.

a means by which a tissue or organism defends its integrity.  Defense mechanisms include barriers, enzymes, binding proteins, antibodies and immune cells.

relative loss of body fluids. Dehydration can be the result of excessive loss of fluid through sweating, vomiting or diarrhea. Alternatively, dehydration can be the result of inadequate fluid intake. Dehydration is often the result of exercise in a warm environment, new arrival at altitude, or exposure to an unusually hot environment. Wikipedia

dehydrated

when the total content of water in the body is less than ideal, the body is dehydrated. This can occur due to inadequate intake and/or excessive fluid loss due to sweating, inhibition of antidiuretic hormone or diarhea.

a general term for conditions of disease and neuronal degradation leading to decreased memory and cognitive skills. Wikipedia

branched projections of the neural cell body (soma) that carry activation and inhibitory current from converging neural input to the soma where an action potential is generated if the membrane potential at the axon hillock reaches threshold.

deoxyribonucleic acid, a genetic code in the form of sequence of nucleic acids (cytosine, guanine, adenine, and thymine). Structured as a double-stranded a helix, DNA encodes specific sequences of amino acids for protein structure. Protein synthesis is regulated in part by translation of DNA to messenger RNA. Wikipedia

a change from a polarized state towards a nonpolarized state. Excitable membranes are polarized, that is they have a charge separation across the membrane. Typically, in muscle and nerve cells, the inside is negative with respect to the outside of the cell. Depolarization is the consequence of opening of specific ion channels that allow a preponderance of negative charge to leave the cell or positive charge to come into the cell. Wikipedia

afterhyperpolarization (noun)

when repolarization occurs at the end of an action potential, the membrane potential will usually hyper polarize (go more negative than the resting potential prior to that action potential). This hyperpolarization is due to prolonged opening of the K⁺ channels, so the membrane potential will move closer to the equilibrium potential for K⁺. 

statistical values that allow quantification of a sample; this includes measures of central tendency (mean, median, and mode) and measures of dispersion (variance, standard deviation, and standard error of the mean). Wikipedia

intermediate filament contributing to the cytoskeleton of cells and the Z-disk of myocytes

the process of growth and maturation from the perspective of the early years when body parts grow;  functions and capabilities expand. This word can have alternative meaning, like change in an object or idea towards completion.

a disease that affects the ability of tissues to take up glucose from the blood.  There are two main forms of diabetes: Type 1 and Type 2.  Type 1 diabetes is also referred to as juvenile diabetes.  This disease appears very early in life and results from inadequate insulin secretion.  Type 2 diabetes, also known as adult onset diabetes, is more common than Type 1 diabetes. This can be a consequence of resistance to the action of insulin or inadequate insulin secretion.  Type 2 diabetes is associated with metabolic syndrome.  Diabetes Canada

the lateral pressure exerted by the blood in the arteries, immediately prior to ejection of blood into the vascular tree by the heart. When blood pressure is measured, two numbers are given. Systolic pressure is the high number and diastolic pressure is the low number.  Blood pressure is typically presented as systolic pressure over diastolic pressure.

a system of nutritional recommendations that provides dietary requirements for vitamins, minerals, and macronutrients.  

when the delivery of a substance within the body is inadequate because its diffusion is not sufficient.  Diffusion of an ion or molecule is dependent on the concentration or partial pressure difference, the distance, size of the particle and solubility.  For example, delivery of oxygen from the alveolar space to the blood may be limited due to inadequate partial pressure difference or thickening of the alveolar wall.

modified calcium channels in the sarcolemma of the transverse-tubules; these channels function as voltage detectors and interact directly with ryanodine receptors, the Ca²⁺ channels of the sarcoplasmic reticulum.

a statistical term referring to how varied the measurements of a given variable are. Examples of measures of dispersion include variance, standard deviation and standard error of the mean. Wikipedia

accelerated production of urine by the kidneys.  When the body has excess water content, the kidneys are regulated to output more water, forming more urine. Wikipedia

pathways splitting into two or more paths. This applies to neural pathways via axons that branch or tubes associated with airway or blood movement. When directions diverge or split to go in more than one direction.

the effectiveness of a drug or toxic chemical can be evaluated by measurement of the anticipated response or outcome relative to the concentration of the drug.   The typical response is sigmoidal, similar to the activity of an enzyme.  Brittanica

a pair of motor axon impulses at a rapid rate, often initiating ballistic muscle activation. The frequency of activation is high to begin with but decreases to a reasonably constant level after the initial high-frequency burst.

Triplet

a sequence of three high frequency action potentials, similar to doublet. 

a technique for assessment of whole body energy cost over days.  Water is composed of hydrogen and oxygen. When these elements are labeled by increasing the amount of special isotopes (preferably nonradioactive, like deuterium (²H) and ¹⁸O), the removal of these isotopes from the body can be followed by evaluating the relative content of these isotopes in body fluids at two different times, usually days apart. This technique is considered quite accurate for assessment of total body energy needs over time.

DEXA is a technique to assess body composition by transmission of X-rays at two energy levels across the body and detection of the % transmission to quantify the density of tissue.  The technique is able to differentiate fat, muscle and bone.  In addition to giving an estimate of % body fat, DEXA can also quantify bone density.  Wikipedia

a device to measure force.  The most common dynamometer used in exercise physiology is the hand-grip dynamometer.  This device measures the grip strength, which is often taken as a general measure of strength.  

an aggregation of transcellular proteins including dystrophin with attachment to the extracellular glycocalyx matrix

cytoskeletal protein of skeletal muscle that inserts into the membrane and via the dystroglycan complex, allows lateral force transmission to the extracellular connective tissue.  Wikipedia

also referred to as Euler’s number, e is equal to the sum of all values for (1+1×n ^-1)ⁿ, where n is the set of integers from 1 to infinity. Euler’s number can be approximated to equal 2.71828182846. e is a constant used for the natural log. In contrast with the log to the base 10, the natural log uses a base of e. Wikipedia

a type of muscle contraction that resists but allows lengthening. The active muscle serves as a brake to slow the rate of lengthening. Also known as a lengthening contraction. Wikipedia

the energy cost of doing a task. Any task can have an economy: walking, running, knee bends, assembly line labour, grocery shopping etc. The utility of the term economy is that it expresses the energy cost relative to a unit of the task. For example, economy of walking is the energy cost to walk a fixed distance. The units of economy are often given in oxygen equivalents, but should be expressed as energy equivalents (joules or kcal).  

the energy cost to move from one position to another, by any mode of locomotion: walk, run, cycle, hand walk. Economy is a convenient term when mechanical work is not easily quantified, or is irrelevant with respect to the objective. Often, economy is expressed as the oxygen equivalent, but for precision should be calculated as an energy (joules or kcal). If the energy cost is body mass dependent, then it should be expressed per kg of body mass.  

a means by which a change is accomplished. An effector can be a molecule that triggers some change in the body, a muscle that accomplishes a change in position or heat generation, any cell that can accomplish a change that is desired, typically by some control mechanism.

refers to going to something. An efferent neuron is one that is goes from the central nervous system to a target organ. Interestingly, the efferent neuron typically will activate an effector, an organ that can bring about change. Wikipedia

referring to or describing the status of a system or circumstance with respect to relative magnitude of useful energy output for a given energy input. 

the ratio expressing conservation of energy, also the ratio of energy out to energy in.  Efficiency is often used to show the relative preservation of energy in the form of mechanical work.  The ratio of work done to energy cost expressed as a percent.  Human exercise can be as much as about 25% efficient. That is, 25% of the energy cost is preserved as work done.  Efficiency of human effort can also be zero if no work is done.  An isometric contraction, for example, accomplishes no work, so the efficiency is zero.  Typical values for efficiency of cycler ergometer exercise is 16-24%, but can be lower than this.  The word, efficiency, is often misused.

a protein of the extracellular matrix with a high degree of elasticity. This protein gives tissues the property of restoring structure after deformation.

any substance that will be charged when dissolved in solution, including potassium, sodium, and chloride.  We have electrolytes in our blood and we consume electrolytes in our food and in sport beverages.  Major electrolytes in the body include: sodium, chloride, potassium, calcium, and magnesium.  Wikipedia

electrochemical gradient

the driving force allowing an ion to cross a membrane; this is a combination of concentration gradient and electromotive force.  For example, Na⁺ is at a high concentration outside the cell and the cell membrane has a charge separation with the inside negative. The combined concentration gradient and charge difference combine to create more movement of Na⁺ across the membrane when the Na⁺ channels open.

electrolyte balance is when the primary electrolytes in the body, including: Na⁺, Cl^-, K⁺, Ca²⁺, H⁺, Pi, HCO^3-, and Mg²⁺are at the proper concentration inside and outside the cells of the body.  This balance depends on intake and output of the individual electrolytes as well as intake and output of water, which can change the concentration of these electrolytes.  Exercise disturbs the balance of electrolytes.

measurement of the muscle activation pattern by electrodes placed on the skin over the muscles or by intramuscular electrodes. EMG detects the waves of depolarization of muscle cells under the electrode(s).  The signal appears to be “noise” but contains information about the number of cells that are active.  Analysis of EMG signals can include a variety of approaches including root mean square, integration, peak to peak magnitude and frequency content.  Wikipedia

electromyogram

The tracing of electrical signals obtained from surface electrodes detecting muscle activation.

a sequence of complexes in the mitochondria, also called electron transport chain, that react with an electron donor (NADH or FADH₂). In the process of transferring the electron between cytochromes and by coupling with proton pumps, H⁺ is transported into the intermembrane space, decreasing pH in this space.  The later transfer of H+ across the inner mitochondrial membrane is coupled with phosphorylation of ADP to ATP.

a chemical technique that involves applying a voltage across a sheet of gel when a solution containing a tissue extract has been placed on the edge of the gel.  The electric current drives the proteins through the gel at a velocity that is proportional to the molecular weight.  This allows separation of the proteins and they can subsequently be identified by staining the gel and comparison with standard molecular weight molecules or transfer to a medium that antibodies can access.

the volume of the ventricle at end diastole, or just before ejection of the stroke volume.  The end diastolic volume is an important determinant of stroke work, the product of volume ejection and pressure of ejection.  End diastolic volume also represents the highest that the stroke volume can be for that beat of the heart. 

the structural parts of the myocyte lying beneath the nerve terminal where the nerve terminal connects (synapses) with the muscle cell, also called motor end-plate. The end-plate includes the sarcolemma and a mound of myoplasm immediately under the sarcolemma (sole-plate) where the nerve terminal sits over that membrane.  

the volume of the ventricle at end of systole, or just after ejection of the stroke volume.  Usually, at rest, the end systolic volume is less than 50% of the end diastolic volume.  During exercise, the end diastolic volume decreases, allowing a greater stroke volume.

a molecular signaling process that relies on specialized cells in the body that release the chemical messenger into the blood. The chemical binds to receptors in some organ that is some distance from the tissue where it is released. The pancreas is an example of an endocrine organ, releasing insulin or glucagon into the blood. These chemical messengers get into the blood and have a variety of effects on cells through-out the body. Wikipedia

the process of taking a tiny volume of extracellular fluid, and its constituents into the cell by formation of a small vesicle.  The surface membrane envelopes the small volume of extracellular fluid, then pinches off to form an internal vesicle. Wikipedia

a thin layer of connective tissue, primarily collagen, around each myocyte. Wikipedia

endoplasmic reticulum:

a membrane bound organelle in various types of cell. Endoplasmic reticulum can be rough (with ribosomes attached) or smooth. Rough endoplasmic reticulum serves as a location for protein synthesis. Smooth endoplasmic reticulum can be a location for Ca2+ storage, hormone synthesis or specialized metabolism. In skeletal muscle, the endoplasmic reticulum is specialized for Ca2+ storage and is called the sarcoplasmic reticulum.

cells lining the heart chambers, blood vessels and lymphatic vessels.  This layer of cells is just one cell thick at the capillary level, but can be 6 cells thick in larger vessels.  

endothelial layer

referring to the endothelial cells as a layer of the blood vessel wall.

the ability to persist with a physical task. Endurance is often evaluated at relative exercise intensity. For example, how long can you exercise at the anaerobic threshold? Wikipedia

endurance training

the performance of regular exercise with the intention of improving endurance (the ability to persist with a task) of a specific movement pattern or form of locomotion.

the difference in energy intake versus energy expenditure.  This represents energy available for extraordinary circumstances or is stored as fat.

when caloric intake is equal to energy expenditure over an extended period of time. For example, this can be indicated by stable body weight.

a measure of the proportion of usable energy from ATP, represented as the following ratio: ([ATP]+.5[ADP])/([ATP]+[ADP]+[AMP]). The value of energy charge can vary from 0 to 1. When the value is close to 1, most of the estimated free energy of hydrolysis for the reaction: ATP ® ADP + Pi is available. When the energy charge decreases, some ATPase reactions are not possible. Wikipedia

the conversion of energy from one form to another. For example, chemical energy is converted to mechanical energy by the myosin ATPase of muscle.  Usually energy transduction has low efficiency and much of the available energy is lost as heat. This is certainly the case in skeletal muscle.  

an enzyme is a protein that accelerates a chemical reaction, by reducing the energy barrier for the reactants to proceed to the products. An enzyme can be activated or inhibited to facilitate or prevent the specific reaction.

also known as fascia, envelopes each muscle in a thick layer of connective tissue.

a hormone of the sympathetic nervous system, also known as adrenaline. Epinephrine accelerates heart rate, increases cardiac contractility and can cause vasodilation or vasoconstriction, depending on the receptor activated. Epinephrine is a catecholamine, and it is also the drug used in an epi-pen for treatment of a strong allergic reaction.  

the theoretical charge separation across a membrane required to maintain the concentration gradient for a given ion if the membrane was freely permeable to that ion.  The equilibrium potential is unique for each ion and is dependent on the concentration gradient at the time.

any food, chemical, substance, or training method that can enhance performance. Common examples of ergogenic aids include drugs like caffeine or anabolic steroids. However, even something like water could be considered an ergogenic aid. Some ergogenic aids are banned by sport governing bodies, others are an accepted part of sport.  

a device for the measurement of work; such a device must take into consideration both force and length change. From the Greek "ergon" (work) and "metron", (measure). Common ergometers include cycle ergometer, rowing ergometer and devices simlar to the Biodex.

the process of synthesis of new red blood cells (erythrocytes).  New red blood cells are created from erythropoietic stem cells, in the bone marrow of the long bones. Regulation of erythrocyte synthesis is under the control of erythropoietin, a hormone secreted by the kidneys.  

a hormone, synthesized in the kidneys in response to hypoxia, that signals the bone marrow to make more red blood cells.  

any dietary substance that is not produced endogenously. We must consume essential nutrients in our diet to ensure adequacy. Wikipedia

the prefix “eu” means neutral, so when someone is euhydrated, it means the individual is neutrally hydrated; does not have more or less water in the body than is necessary or expected.  

euhydration (noun):

the state of having the expected amount of water in the body

adequate breathing or alveolar ventilation for the metabolic state of the body.

an international organization that promotes knowledge and awareness of the science of sports.  The ECSS organizes an International conference each year where scientists can present their latest research to their peers.  

the conversion of a liquid to a gaseous state. Evaporation absorbs heat, so evaporation of sweat from the skin will cool the skin, ridding the body of heat that was generated during exercise.  

evaporate (verb):

the transition from fluid to gas state. When sweat evaporates from your skin, the energy for this transition of state comes from the heat of the body, thereby cooling the body.

evaporative (adjective)

referring to the mechanism as evaporation

the total oxygen uptake, above the resting level that is taken into the body during the time immediately after an exercise, that is accumulated until the rate of oxygen uptake returns to the resting level. This is also called the recovery oxygen uptake. Note, this is an amount, not a rate. Wikipedia

the signaling process from generation of an action potential on the muscle membrane to initiation of contraction is known as excitation-contraction coupling (E-CC). This includes the propagation of the action potential along the surface membrane and into the transverse tubules; detection of a membrane voltage change by the dihydropyridine receptors and subsequent opening of the ryanodine receptors which are the Ca²⁺ release channels of the terminal cisternae. Opening of the ryanodine receptors results in diffusion of Ca²⁺ from the sarcoplasmic reticulum into the myoplasm. Ca²⁺ binds to several proteins including: troponin C, parvalbumin, SERCA and Ca²⁺ exchangers. The binding of Ca²⁺ to troponin C results in motion of tropomyosin, the consequence of which is exposing the binding site for the myosin heads on actin.  Muscle contraction can then occur. Ca²⁺ is removed from the myoplasm by SERCA and Ca²⁺ exchangers. Once [Ca²⁺] falls to resting values, Ca²⁺ dissociates from troponin C and tropomyosin moves back to obscure the myosin binding sites on actin. 

Excitation (noun); Excite or Activate (verb)

The process of bringing the state of a cell from a resting condition to one of generation of an action potential.

planned, systematic physical activity, with the purpose of improving fitness and/or health

exercise hyperventilation (also called hyperpnea)

hyperventilation is essentially an elevated ventilation, beyond that needed for support of metabolic use of oxygen. During submaximal exercise, up to approximately anaerobic threshold, ventilation increases in proportion to the metabolic demand of the exercise. However, when the exercise intensity increases beyond the anaerobic threshold, ventilation increases exponentially; when ventilation is in excess of that which would be proportional to the metabolic demand, then it is considered to be hyperventilation. A consequence of hyperventilation is that more CO₂ is removed from the body than is produced by metabolic processes.  

exercise physiology

briefly, exercise physiology is the study of how the body adjusts acutely and adapts chronically to the challenge of maintaining the internal milieu during exercise. Wikipedia

the process of taking a tiny volume of intracellular fluid, and its constituents out of the cell by extrusion of the contents of a small vesicle.  The vesicle membrane fuses with the cell membrane, extruding its contents to the extracellular space.

an experimental study is an investigative research project that manipulates the test subjects or imposes an intervention to test an hypothesis.  Random assignment of subjects to treatment groups is an important aspect of the experimental study format.

quasi-experimental study:

Similar to an experimental study, but lacking true randomization of subjects from the population of interest to the treatment groups. 

the act of exhaling air from the lungs.

the air that can be exhaled during maximal effort after a normal expiration.

when the change in value of one variable changes in proportion to its current value with progressive change in the value of another variable. The slope of this relationship keeps changing.  

that a research conclusion can be applied more generally than to the specific population under study. This is an important aspect of research in exercise physiology. For example, a study of the adaptation to training in a group of Kinesiology students may not apply to an apparently similar group of engineering students.

refers to the space or volume in the body that lies outside the cells. This includes not only the space between cells in the various organs, but also the plasma; part of the blood that is not cells. Wikipedia

extracellular fluid (ECF)

the fluid that occupies the space between cells. Extracellular fluid typically has high concentration of sodium and low concentration of potassium

are the voluntary muscle fibres that respond to activation of the α motoneuron. They are called extrafusal, in contrast with intrafusal, because they are located outside the spindle. Wikipedia

the electric charge of one mole of electrons or 96485.332132 coulombs per mole. One coulomb is the amount of electricity transferred at 1 amp for 1 s.

bundles of cells in a muscle. A fascicle is a group of muscle cells, bound by epimysium. Note that cells from several motor units can exist in a given fascicle.  

a fibre-type classification of skeletal muscle cells with a high maximal velocity of shortening and a short time to peak tension for a twitch. Myosin isoform associated with fast-twitch is type II myosin (a or x for human muscle). Small mammals also have IIb myosin. The actual time to peak tension of the twitch varies by species, indicating that factors other than myosin isoform contribute to this characteristic.  

making up a substantial part of the body and serving the function of metabolic substrate reserve, protection of internal organs.  Fats (lipid) are various sized molecules of carbon and hydrogen, including: phospholipids, cholesterol and triglycerides. Fats provide 9 kcal×g^-1 of energy when fully oxidized. 

 Wikipedia

fatty acid. 

a common form of fat in the body, often used in metabolism to provide energy for exercise. A fatty acid is a carbon chain with 1 oxygen and 2 hydrogen atoms for each carbon. 

the mass of the body, exclusive of fat.  This would include bone, skin, internal organs, muscle and brain.  Fat-free mass is often calculated, based on estimation of total fat content subtracted from body mass.

though often defined as reduced capacity for force generation, this definition of fatigue is too restricted. Fatigue is impaired force generation for a given stimulation, usually as a consequence of prior activation. This definition allows detection of low-frequency fatigue.

fatigue index: 

a mathematical expression of the magnitude of fatigue. The ratio of the force at the end of a period of fatiguing contractions to the force at the beginning, often expressed as a %.  For example, if the force decreases to 45% of the initial force, then the fatigue index is .45 or 45%.

a regulatory process that relies on sensory input to control something at a set level. Feedback control relies on sensors, that detect something like temperature or pH, and a controller that has a means of effecting change to that variable; increasing it when it is detected to be low and decreasing it when it is detected to be high, relative to the set point.  

a regulatory process that relies on anticipation of an impending disturbance to the value of some variable and effecting change before or as that disturbance would have occurred. An example of feed-forward control is the regulation of ventilation at the beginning of exercise. Signals from the motor cortex (or premotor cortex) to the ventilatory control center allow an increase in ventilation can be effected as the exercise is started.  

a condition found in some female athletes who are in a negative energy balance due to over training and under nutrition. The three symptoms of the triad include amenorrhea, loss of bone mineral density, and disordered eating. Wikipedia

a term used to classify skeletal muscle fibre properties; typically fast-twitch and slow-twitch, based on myosin isoform in mammalian muscle. Adult human muscle can be identified as type I, type IIa, and type IIx according to the presence of these three isoforms of myosin. Hybrid fibres have more than one isoform of myosin present. There is also a classification that relies on contractile and metabolic properties.  

type I fibre: 

skeletal muscle fibre-type represented with type I myosin.  Type I myosin has a slow ATPase activity and is typically a high oxidative fibre. 

type IIa fibre: 

 skeletal muscle fibre-type represented with type IIa myosin which is a fast-twitch phenotype with a high myosin ATPase activity.  Type IIa fibres will typically have a high oxidative capacity.

type IIb fibre: 

 skeletal muscle fibre-type represented with type IIb myosin which is a fast-twitch phenotype with a high myosin ATPase activity.  Type IIb fibres will typically have a low oxidative capacity and will fatigue quickly.  Human muscles do not contain type IIb fibres, but prior to 1999, type IIx fibres were called type IIb (in human biopsy material). 

type IIc fibre:

hybrid muscle fibre fibre-type with type I and type IIa myosin in the same fibre. Type IIc fibres were identified by histochemical staining for myosin ATPase and were initially thought to be an independent fibre-type.  Staining for antibodies confirmed that these fibres were hybrid fibres.

type IIx fibre: 

skeletal muscle fibre-type represented with type IIx myosin which is a fast-twtich phenotype with a high myosin ATPase activity.  Type IIx fibres will have a low oxidative capacity and will fatigue quickly.  Human muscles do contain type IIx fibres, but typically a small proportion of the cross-section is occupied by this fibre-type.

the amount of gas moving across a sheet of tissue is proportional to its surface area and inversely proportional to its thickness. Wikipedia

the general Fick equation (V(dot)O₂ = Q(dot)a×O₂-Q(dot)v×O₂ or Q(dot)×(aO₂-vO₂) is based on the principle that the amount of substance taken up by an organ (or organism) is equal to the amount delivered minus the amount coming out.  In the case of an organ (like a kidney or a muscle), the oxygen uptake is equal to the amount of oxygen in the blood going into the kidney or muscle minus the amount coming out, in a given time.  

Where the (dot) represents per minute, Q(dot) is blood flow, aO₂ is arterial oxygen content and vO₂ is venous oxygen content.  In the case of the whole body, Q(dot) represents cardiac output and v would be mixed venous.

the Fick principle is the underlying principle of the Fick equation.  The general Fick equation is based on the principle that the amount of substance taken up by an organ (or organism) is equal to the amount delivered minus the amount coming out.  

physical fitness is a term referring to generalized health and capability.  In reality, fitness is specific for a task, and fitness assessment will evaluate several components of health and capability including cardiovascular health, strength, flexibility, and pulmonary health.  

also called an isometric contraction, a contraction for which the ends of the muscle are held in a constant position, such that the length of the muscle-tendon unit does not change.  During a fixed-end contraction, the fascicles shorten and the tendons lengthen.

sensory neurons carrying information from pain receptors (nociceptors) in the periphery with multisynaptic input to the central nervous system, result in activation of ipsilateral flexor muscles, inhibition of ipsilateral extensors and activation of contralateral extensors.

fluid or liquid is a state of matter that can flow or occupy a container with irregular boundaries. Fluid intake is the amount of fluid consumed including the water content of solid foods.  CDC fluid intake

fluid balance

keeping the total amount of water in the body at the correct amount would be considered fluid balance.  This keeps the concentration of electrolytes, proteins, hormones, and other molecules at the proper range. Fluid balance relies on intake in food and fluids and output including urine, feces, sweat, and ventilation.

the quantifiable relationship between [Ca²⁺] and isometric force. This relationship is typically determined by immersing a skinned fibre (whole myocyte, with a disrupted membrane) in a solution that mimics intracellular fluid but for which [Ca²⁺] is known. When a variety of Ca²⁺ concentrations are tested, the relationship can be constructed.  Intact fibres can also be tested for this relationship by stimulating at a variety of frequencies.  The relationship between force and [Ca²⁺] is sigmoidal.  In many cases, the relationship is expressed with the negative log of [Ca²⁺].

the dependence of isometric force on frequency of activation. As frequency increases, isometric force of contraction increases in a sigmoidal fashion.  

the dependence of isometric force on the sarcomere length of the muscle. When sarcomere length is as short as it can be (the length of the myosin filament), active force is zero. As sarcomere length increases, active force increases up to the sarcomere length with optimal overlap of the filaments, then active force decreases as sarcomere length increases beyond this. In mammalian muscle, myosin filaments are 1.6 mm long and actin filaments are 1.0 mm.  

the relationship between force generation and velocity of the shortening of a muscle (fibre, motor unit, whole muscle, or muscle group). The relationship is characteristically hyperbolic with a secondary curvature near the isometric state. The force-velocity relationship can be defined by maximal isometric force, maximal velocity of shortening, and curvature of the relationship.  

the volume of air forcefully expelled from the fully inflated lungs until no air can be further exhaled. The forced vital capacity is used as a clinical measure to quantify not only the volume of air that can be moved into or out of the lungs but also the relative resistance of the airways.

a break in the continuity of a bone. A fracture can be a crack or a complete dissociation of a bone into two or more parts. A compound fracture is a break of a bone that results in a portion of bone piercing the skin. To fracture a bone (verb) is to break a bone. As a verb, fracture means to break.

a highly reactive molecule (or atom) with unpaired electrons that is usually formed with interactions with oxygen. Wikipedia

the state of the body that allows pursuit of normal and desired activities without pain. An absence of injury or disease that would hamper mobility and the ability to do not only the essentials of life, but also the things you would like to do.

spindle-shaped muscle fibres that lie in parallel with the line of action of a muscle. Individual muscle fibres are wider near the middle than at the ends, giving the whole muscle this tapered structure.

a hormone receptor embedded in a membrane that responds to hormone binding by activating a guanosine nucleotide dependent enzyme, usually resulting in second messenger formation, like increased cyclic adenosine monophosphate concentration.

efferent neuron originating in the ventral horn of the spinal cord and innervating the muscle spindle.  Activation of the gmotor neuron will stiffen the spindle, accentuating its response (frequency of afferent signaling) to length change.

Gatorade is a sport beverage, initially formulated by Robert Cade, a Renal Physiologist from the University of Florida.  The constituents of Gatorade were prepared to replenish fluid and electrolyte loss of the University of Florida Gator football team. 

Gatorade Sport Science Institute: 

the Gatorade Sport Science Institute is an organization that supports collaborations for education and research on the sport sciences.  The original focus was related to Gatorade, but the breadth of topics has been increased to include a broad range of sport science topics. GSSI

the process by which the heritable information of a gene is expressed as a functional product. The first step of this process is transcription where the gene is copied into a messenger RNA (mRNA). The mRNA is translated into a protein which has a specific function in the cell.

a hormone released from the pancreas in response to low blood glucose concentration. Glucagon has effects in many parts of the body and generally increases blood glucose. Wikipedia

glucocorticoid

steroid based hormones (cortisol) and drugs (prednisone, cortisone) with anti-inflammatory effects

the formation of new glucose. Gluconeogenesis occurs in the liver and kidneys, and can convert amino acids to glucose. Though not strictly “new”, formation of glucose from lactate and pyruvate is also considered gluconeogenesis. Wikipedia

a tool used to classify carbohydrates on their ability to raise blood glucose. The GI classifies food on the rate in which blood glucose rises when compared to 100 g of glucose. Wikipedia

a polymer of glucose units serving as storage of this valuable carbohydrate, primarily in liver and muscle.  

glycogen granule: 

glucose units bind together in a branching manner and these structures become large enough to see in electron microscopy. They are referred to as glycogen granules.

the hydrolysis of glucose units from a glycogen molecule. Wikipedia

the sequential breakdown of glucose in an energy conserving manner, resulting in the phosphorylation of ADP to form ATP. The end product of glycolysis is pyruvate or lactate. Wikipedia

glycolytic (adjective)

relating to glycolysis, the metabolic pathway for synthesis of ATP from glucose, resulting in the formation of pyruvate or lactate

sensory receptor, detecting force exerted on a tendon.  A Golgi tendon organ is a series of nerve endings that respond with increasing frequency of action potentials in proportion to the force exerted on the tendon.  Afferent neurons (type IIb) carry the action potentials to the central nervous system and in addition to synapsing with nerves to the brain, also synapse with ipsilateral motor neurons and inhibit activation of the muscle attached to that tendon.

when the membrane potential changes gradually, and to varying amounts, with only passive spread, the potential is considered to be graded.

a diagram depicting the quantitative relationship between at least two variables that shows how one (dependent variable) changes in response to changes in the other (independent variable). Three-dimensional graphs show the interrelationship between three variables. An example of a graph is the diagram depicting the relationship between oxygen saturation and partial pressure of oxygen. This graph shows that as partial pressure increases from 0 to 100 mm Hg, oxygen saturation increases slowly at low partial pressures, but sharply between 20 mm Hg and 50 mm Hg, then more slowly again, reaching a plateau of full saturation at 100 mm Hg. Wikipedia