Exercise Physiology Review: Muscular, Skeletal, Cardiac, Respiratory, Neuromuscular, Endocrine Systems and Energy Pathways (Vocabulary Flashcards)

A comprehensive set of key vocabulary terms and definitions drawn from the lecture notes to support exam preparation across muscular, skeletal, cardio-pulmonary, neuromuscular, endocrine, and energy-system concepts.

Recruitment order of muscle fibres

During increasing exercise demand, slow-twitch (Type I) fibres are recruited first, followed by fast-twitch Type IIa, then Type IIx; only a fraction are recruited at any time to prevent damage.

Cardiac output (CO)

Volume of blood pumped by the heart per minute; at rest ~5–6 L; during maximal exercise ~15–20 L; redistribution to muscles via vasoconstriction/dilation.

Vasodilation

Increase in diameter of blood vessels, increasing blood flow to the muscles.

Vasoconstriction

Decrease in diameter of blood vessels, reducing blood flow to non-essential tissues during intense exercise.

Oxygen uptake difference (a-vO2 diff)

Difference in oxygen content between arterial and venous blood; increases with exercise as muscles extract more O2.

Sinoatrial node (SAN)

Heart's natural pacemaker; heart rate modulated by sympathetic (noradrenaline) and parasympathetic (acetylcholine) input.

Q = SV × HR

Equation for cardiac output; stroke volume times heart rate.

Stroke volume (SV)

Amount of blood pumped by the left ventricle per beat; typically ~70–80 mL; trained athletes may reach ~110 mL.

Starling’s law

Stroke volume increases with greater end-diastolic volume (preload) due to greater stretch of cardiac muscle.

Systolic blood pressure

Pressure in arteries during heart contraction; rises with activity; resting range ~110–140 mm Hg.

Diastolic blood pressure

Arterial pressure during heart relaxation; typically 70–80 mm Hg at rest and may stay the same or decrease slightly during exercise.

Blood pH during exercise

pH generally 7.2–7.5 in blood; exercise can lower pH (more acidic) due to CO2 and lactate.

Oxygen dissociation curve

Relation between oxygen saturation and partial pressure of O2; shifts with temperature and pH to unload O2 to active muscles.

Gaseous Exchange

Gas exchange efficiency in the lungs; increases with exercise to maintain O2 delivery and CO2 removal.

Tidal volume (VT)

Volume of air per breath; rest ~0.4 L; can reach ~1 L in average adults and ~2 L in elite athletes during exercise.

Minute ventilation (VE)

VT × respiratory rate; total air moved per minute; can rise from rest values to 40–60 L/min during moderate exercise.

Alveolar ventilation efficiency during steady-state exercise

Deeper breathing (larger VT) with only modest RR increase; results in higher alveolar ventilation and CO2 removal.

Oxygen diffusion during exercise

Increased diffusion of O2 from capillaries to muscles as demand rises and diffusion gradients are greater.

Anaerobic glycolysis

Glycolysis without oxygen; glycogen breakdown yields ATP and lactate; lactate accumulation limits high-intensity efforts.

Glycolysis products

Pyruvic acid produced; under anaerobic conditions, converted to lactic acid (lactate and H+).

NAD+/NADH in glycolysis

NAD+ accepts H+ during glycolysis; becomes NADH; during ETC NADH donates H+ for ATP production.

Lactic acid

Dissociates into lactate and H+; accumulation lowers muscle pH and contributes to fatigue.

OBLA (onset of blood lactate accumulation)

Point where lactate starts to accumulate in the blood; higher % VO2max in trained athletes.

Krebs cycle (Citric acid cycle)

Aerobic cycle in mitochondria that processes acetyl-CoA to CO2 and H+ carriers; generates NADH for ETC.

Electron Transport Chain (ETC)

Series of aerobic reactions in mitochondria where hydrogen from Krebs is used to produce large amounts of ATP; final acceptor is oxygen.

ATP-PC system

Immediate, anaerobic energy system using phosphocreatine (PC); dominant for the first seconds of all-out effort; 3–15 s capacity.

Phosphocreatine (PC)

High-energy phosphate reservoir that donates phosphate to ADP to form ATP during short, explosive efforts.

Creatine kinase

Enzyme that catalyses PC breakdown to rapidly replenish ATP.

Glycogen/glycolysis

Glycolysis breaks down glucose; in aerobic conditions, pyruvate enters Krebs; in anaerobic conditions, lactate is produced.

Lactate and hydrogen ions (H+)

By-products of anaerobic metabolism; accumulation lowers pH and impairs muscle contraction if not cleared.

Gluconeogenesis

Liver conversion of lactate to glucose; part of EPOC restoration processes.

Myoglobin

Oxygen-storage protein in muscle; releases O2 to mitochondria during demand.

Mitochondria

Cellular organelles where aerobic metabolism occurs; more mitochondria improve oxidative capacity.

Capillarisation

Increase in capillary density around muscles; enhances oxygen delivery and CO2 removal.

Endurance training adaptations

Increased mitochondrial density, myoglobin, capillarisation, and oxidative enzymes; improved fat oxidation.

Strength training adaptations

Increased contractile proteins, cross-sectional area, tendon/ligament strength, and neural recruitment.

VO2 max

Maximum rate of oxygen consumption; indicator of cardiovascular fitness and endurance potential.

RER (Respiratory Exchange Ratio)

Ratio of CO2 produced to O2 consumed; reflects substrate use and can exceed 1 during high-intensity exercise.

Overtraining

Excessive training with insufficient recovery causing performance decline, fatigue, immune suppression and sleep disruption.

EPOC (Excess Post-exercise Oxygen Consumption)

Elevated oxygen intake after exercise to restore phosphagen stores (fast component) and remove lactate (slow component).

Gluconeogenesis (recovery context)

Lactate-to-glucose conversion during EPOC restoration, aiding fuel replenishment.

Glycogen replenishment

Restoration of muscle and liver glycogen stores; fastest in the first hours post-exercise; aided by carbohydrates.

Protein for recovery

Adequate protein intake (~20% of daily intake) supports muscle repair after training and competition.

Carbohydrate needs

Carbohydrates commonly ~70% of daily intake; nutrition planning aligns with training load and events.

Hydration

Maintaining fluid balance is essential to prevent fatigue; replenish fluids according to thirst and not excessively.

Altitude adaptations (short-term)

Hyperventilation, tachycardia, mild VO2max reduction; capillary changes occur with acclimatisation.

Altitude adaptations (long-term)

Increased capillaries, myoglobin, mitochondria, oxidative enzymes; RBC adaptations improve O2 delivery.

Sleep high, train low

Altitude training strategy: sleep at altitude but train at lower altitude to gain RBC benefits without reducing training intensity.

Thermoregulation (methods)

Heat loss via conduction, convection, radiation, and evaporation; sweating increases to cool the body.

Conduction

Heat transfer through direct contact with a surface.

Convection

Heat transfer via moving air or water around the body.

Radiation

Heat transfer through infrared waves to cooler objects without contact.

Evaporation

Heat loss through evaporation of sweat; major mechanism during exercise.

Hyperthermia

Inability to dissipate heat; core temperature > ~40°C; risk of organ damage; sweating may be insufficient.

Hypothermia

Core temperature drops; shivering and reduced metabolic rate; can be life-threatening as temperature falls.

Frostbite

Tissue damage from freezing temperatures due to prolonged exposure; requires rapid rewarming.

Dehydration

Excessive fluid loss; reduces plasma volume and impairs performance; electrolyte replacement is important.

Baroreceptors

Pressure-sensing vessels that help regulate blood pressure and influence cardiac output.

Chemoreceptors

Detect chemical changes (e.g., CO2) to regulate breathing rate and depth.

Thermoreceptors

Sense changes in temperature to trigger thermoregulatory responses.

GTOs (Golgi tendon organs)

Proprioceptors in tendons that sense tendon stretch and aid in relaxing muscles to prevent injury.

Muscle spindles

Proprioceptors within muscle fibers (intrafusal fibers) that detect stretch and velocity; trigger reflex contraction to protect muscle.

Intrafusal fibers

Specialized muscle fibers inside the muscle spindle that detect stretch.

Proprioceptors

Sensory receptors that provide the brain with information about body position and movement.

Sliding filament theory (calcium role)

Calcium release enables actin-myosin cross-bridging and muscle contraction; regulated by neural input.