Exercise Physiology: Muscle Structure, Bioenergetics, Cardiovascular Control, and Training Adaptations

Vocabulary flashcards testing key anatomical, metabolic, cardiovascular, and exercise training terms grounded directly in the physiology lecture materials.

Epimysium

The outer connective tissue layer surrounding the entire skeletal muscle.

Perimysium

The connective tissue sheath that surrounds each muscle fascicle (bundle of muscle fibers).

Endomysium

The fine layer of connective tissue surrounding each individual muscle cell or muscle fiber.

Sarcomere

The basic functional and contractile unit of skeletal muscle, bounded by Z-disks and composed of actin and myosin protein filaments.

Titin

A spring-like third myofilament extending from the Z-disk to the M-band that stabilizes sarcomeres, centers myosin, and increases stiffness when activated to prevent overstretching.

Motor Unit

A functional unit consisting of a single $\text{α}$-motor neuron and all the muscle fibers it innervates.

Type I Muscle Fibers

Slow-twitch muscle fibers with high oxidative capacity and high fatigue resistance, reaching peak tension in $110\,ms$.

Type IIa Muscle Fibers

Fast-twitch oxidative/glycolytic (FOG) muscle fibers featuring high glycolytic capacity, moderately high oxidative capacity, and fast contractile speed ($50\,ms$ peak tension).

Type IIx Muscle Fibers

Fast-twitch glycolytic (FG) muscle fibers with the highest glycolytic capacity, low fatigue resistance, and fast contractile speed ($50\,ms$ peak tension).

Size Principle

The principle stating that motor units are recruited in an orderly sequence according to the size of their $\text{α}$-motor neuron, starting with the smallest (Type I) followed by midsize (Type IIa) and largest (Type IIx).

Static (Isometric) Contraction

A muscle contraction where force is generated without changing muscle length or joint angle.

Concentric Contraction

A dynamic muscle contraction during which the muscle shortens while generating force.

Eccentric Contraction

A dynamic muscle contraction during which the muscle lengthens while developing force.

Bioenergetics

The cellular process of converting food substrates (carbohydrates, fats, and proteins) into usable biological energy ($ATP$).

Glycogenolysis

The biochemical breakdown of stored glycogen into glucose in the liver and active muscle tissue.

Basal Metabolic Rate (BMR)

The minimum rate of energy expenditure required to sustain basic life functions at rest, measured in a supine position in a thermoneutral environment after $8\,h$ of sleep and $12\,h$ of fasting.

Resting Metabolic Rate (RMR)

A practical measure of resting energy expenditure similar to BMR (within $5\%$ to $10\%$) but measured under less stringent standardized conditions, typically ranging between $1,200$ and $2,400\,kcal/day$.

Maximal Oxygen Uptake ($\dot{V}O_{2\max}$)

The highest rate of oxygen consumption achievable during maximal dynamic exercise, representing the best single measurement of cardiorespiratory endurance fitness.

Excess Postexercise Oxygen Consumption (EPOC)

The elevated rate of oxygen consumption above resting values during early recovery used to replenish $ATP$/$PCr$ stores, clear $CO_2$, convert lactate to glycogen, and resaturate myoglobin.

Lactate Threshold

The exercise intensity or workload at which blood lactate accumulation increases markedly above baseline because production exceeds the clearance rate.

Delayed-Onset Muscle Soreness (DOMS)

Muscle distress and stiffness appearing $1$ to $2$ days after an exercise bout, primarily triggered by structural cell membrane and Z-disk damage from intense eccentric contractions.

Sinoatrial (SA) Node

The specialized cardiac pacemaker tissue in the upper posterior right atrium that spontaneously generates action potentials to initiate cardiac contraction.

Atrioventricular (AV) Node

The cardiac conduction element located in the right atrium wall that delays and relays electrical impulses from the atria to the ventricles.

Electrocardiogram (ECG)

A graphical recording of the electrical activity of the heart obtained using $10$ surface electrodes to record $12$ distinct electrical views (leads).

Stroke Volume (SV)

The volume of blood pumped out of the left ventricle during a single heart beat, calculated as end-diastolic volume minus end-systolic volume ($SV = EDV - ESV$).

Ejection Fraction (EF)

The fraction or percentage of end-diastolic volume ejected from the ventricle during systole ($EF = \frac{SV}{EDV} \times 100$).

Cardiac Output ($\dot{Q}$)

The total volume of blood pumped by the ventricle per minute, calculated as heart rate multiplied by stroke volume ($\dot{Q} = HR \times SV$).

Hematocrit

The percentage of total blood volume composed of formed elements (over $99\%$ of which are red blood cells), averaging around $40\%$ to $45\%$.

1-Repetition Maximum (1RM)

The maximal weight or resistance that an individual can lift through a full range of motion for a single effort with proper execution.

Muscular Power

The rate of performing physical work, defined as force multiplied by velocity or distance divided by time ($\text{Power} = \text{Force} \times \left(\frac{\text{Distance}}{\text{Time}}\right)$).

Principle of Progressive Overload

The training principle specifying that the demands on the body must be systematically increased beyond normal loading to drive further physiological adaptation and performance gain.

Principle of Periodization

The systematic variation of training parameters (intensity, volume, and mode) across structured macrocycles and mesocycles to optimize adaptations and prevent overtraining.

Plyometrics

A form of stretch-shortening cycle training that uses the stretch reflex to recruit motor units and store elastic energy during eccentric movement prior to explosive concentric contraction.

Cam-Based Weight Machines

Variable-resistance strength equipment utilizing an asymmetrical cam to adjust distance from the pivot point, reducing resistance at the start and end of motion to mimic the body's natural strength curve.

Fartlek Training

Continuous endurance training where the athlete randomly varies their running pace between fast sprints and slow recovery jogs based on feeling and terrain.