KINS 1120: Musculoskeletal Fitness (MSK)

Comprehensive vocabulary flashcards covering musculoskeletal fitness, muscle anatomy, motor units, fibre types, exercise adaptations, and age-related changes from KINS 1120.

Musculoskeletal System

The bodily system relating to the musculature and skeleton together, composed of bones, muscles, tendons, ligaments, and soft tissue.

Muscle Fibres

Specialized contractile cells that are long and narrow when relaxed, organized into tissues that move body parts or temporarily alter the shape of internal organs.

Muscular Strength

The amount of force a muscle can produce with a single maximum effort ($1\text{RM}$), typically developed through heavy weight and few repetitions.

Muscular Endurance

The ability of a muscle or group of muscles to remain contracted or to contract repeatedly for an extended period, typically trained using light weight and many repetitions.

Muscular Power

The ability to produce force quickly, calculated by multiplying the force of the contraction by the speed of the contraction ($\text{Force} \times \text{Speed}$).

Myofibrils

Smaller structural units that make up individual muscle fibres, which increase in number in response to strength training to enlarge muscle fibre size.

Muscle Fascicle

A bundle of individual muscle fibres grouped together; multiple fascicles bundled together form a whole muscle.

Motor Unit

A functional motor entity composed of a single motor neuron and the specific group of muscle fibres it innervates.

Fine Control Motor Units

Motor units containing very few muscle fibres that allow delicate, precise movements, such as $10\text{--}20$ fibres per unit in the eye and $10\text{ to }340$ fibres in the fingers.

Powerful Movement Motor Units

Motor units innervating large numbers of muscle fibres for strong, simple movements, such as thousands of fibres in the quadriceps and $2000$ fibres in the gastrocnemius.

Slow Oxidative Fibres (Type I)

Muscle fibres characterized by slow nerve conduction velocity, slow contraction speed, low force and power output, and high fatigue resistance and endurance.

Fast Oxidative Glycolytic Fibres (Type IIa)

Intermediate muscle fibres possessing fast conduction velocity and fast contraction speed, combined with intermediate force production, intermediate/high power output, and intermediate/low fatigue resistance and endurance.

Fast Glycolytic Fibres (Type IIx)

Rapidly contracting muscle fibres with fast nerve conduction velocity, high force production, and high power output that fatigue quickly and exhibit low endurance.

Aerobic Endurance Exercise Adaptation

An exercise-induced transformation that alters the fibre type ratio by converting fast glycolytic (Type IIx) fibres into fast oxidative glycolytic (Type IIa) fibres without changing total fibre count.

Anaerobic Resistance Exercise Adaptation

A muscular training response that increases the size and contractile strength of Fast Glycolytic (Type IIx) fibres without altering the absolute number of muscle fibres.

Hypertrophy

An increase in the cross-sectional size of individual muscle fibres, typically stimulated by mechanical muscle overload.

Atrophy

A decrease in the cross-sectional size of individual muscle fibres, usually caused by inactivity in accordance with the principle of reversibility.

Sarcopenia

The age-related loss of skeletal muscle mass, muscular strength, and physical function.

Post-30 Structural Muscle Changes

Age-related physiological declines occurring after age $30$, including decreased cross-sectional area of individual muscles, reduced muscle density, reduced tendon compliance, and increased intramuscular fat.

Functional Consequences of Age-Related Muscle Loss

Clinical and functional risks linked to aging muscle, including increased bone fragility, higher risk of falls and fractures, increased incidence of osteopenia and osteoporosis, loss of daily independence, and long-term disability.