Muscle Physiology and Athletic Performance

Flashcards covering muscle fiber types, contraction mechanics, metabolic processes, and related medical conditions based on the lecture transcript.

Fast twitch fibers

Muscle fibers that have a fast variant of myosin ATPase, initiate contraction quickly, and have great power and speed, but are considered fatiguable.

Slow twitch fibers

Endurance or fatigue resistant muscle fibers that have a different variant of myosin ATPase and provide low power and slow speed for a long duration.

Oxidative fibers

Fibers that use aerobic respiration (glycolysis, Krebs cycle, and electron transport chain) with oxygen to produce $ATP$ and are fatigue resistant.

Glycolytic fibers

Fibers that use glycolysis for $ATP$ production, fatigue easily, and provide high power and speed for a short duration.

Slow oxidative fibers (Type I)

Fibers that appear dark in color, are fatigue resistant, use aerobic respiration for $ATP$ supply, and contain a slow ATPase.

Fast oxidative fibers (Type II)

Intermediate fibers for middle-distance activities that produce fast and powerful contractions and can perform with lower oxygen delivery.

Fast glycolytic fibers (Type IIb)

The largest muscle fibers in size that fatigue very quickly (about $10$ to $15$ seconds), appear white in color, and produce highest power and speed.

Muscle tension

The force generated when a muscle is stimulated to contract, often measured using a myogram.

Latent period

The time needed to initiate tension in a fiber after stimulation but before contraction begins, during which there is no change in fiber length.

Isotonic muscle contraction

A contraction where the muscle shortens as it gains tension, such as when lifting an object or performing a sit-up.

Eccentric contraction

A type of contraction where the muscle lengthens as it gains tension, such as when running downhill.

Isometric contraction

A contraction where the muscle's length does not change even though it gains tension, like trying to move an immovable object.

Isokinetic contraction

Contractions that cause the muscle to shorten as it gains tension but require a constant speed, often facilitated by machines like a treadmill.

Hypertrophy

An increase in the size of muscle cells resulting from repetitive stimulation, leading to more mitochondria and larger glycogen reserves.

Hyperplasia

The formation of new muscle cells, which is very limited in humans during adulthood and typically occurs only during early growth and development.

Atrophy

A decrease in muscle fiber size resulting from a lack of exercise or temporary reduction in muscle use.

Tetanus

A form of spastic paralysis caused by $Clostridium\,tetani$ where antagonistic muscle pairs contract at the same time due to overstimulation.

Botulism toxin

A toxin from a $Clostridium$ species that causes flaccid paralysis by blocking acetylcholine receptors.

Myasthenia gravis

An autoimmune disease where the body destroys acetylcholine receptors at the neuromuscular junction, leading to muscle weakness and fatigue.

Beta oxidation of fat

The process where fat is used as fuel for $ATP$ synthesis when carbohydrates are not available or are depleted, requiring oxygen.

Net gain from the Krebs cycle (per transcript)

The production of $10$ molecules of $NADH$, $2$ molecules of $FADH_2$, $6$ molecules of $ATP$, and $6$ molecules of $CO_2$.

Clonus

Muscle contraction that occurs independent of voluntary stimulation, often due to fatigue, stress, or lack of blood flow.

Antagonists

Pairs of muscles that work in opposition to each other, such as the biceps which bend the arm and the triceps which extend it.