Biomechanics Set 1

When does muscle strength peak in humans?

Muscle strength peaks between 20 and 30 years of age.

What is one factor contributing to the decrease in muscle strength with increasing age?

Deterioration of muscle mass.

How do muscle fibers change with increasing age, leading to decreased strength?

There is a decrease in muscle fiber size and number.

What changes in body tissue contribute to decreased muscle strength in older individuals?

Increases in connective tissue and fat.

How does vascularization impact muscle strength as people age?

Decreased vascularization contributes to reduced strength.

What happens to the force generation capacity of muscles with increasing age?

There are alterations in force generation.

How does respiratory capacity of muscles change with age, affecting strength?

Decreased respiratory capacity of muscles contributes to reduced strength.

What is a primary reason for decreased muscle power with increased age?

Reduced muscle mass.

What changes in muscle composition contribute to decreased muscle power with age?

Changes in composition of the muscle itself.

How does reduced strength specifically affect muscle power in older adults?

Reduced strength directly contributes to decreased muscle power.

How does muscular endurance compare to muscle strength or power in advanced age?

Muscular endurance is maintained better than muscle strength or power throughout advanced age.

How does age generally affect strength?

Strength generally decreases with age.

How does gender generally affect strength?

Men are generally stronger than women.

What are some individual differences that affect strength?

Individual differences include genetics, lifestyle, and nutrition.

How do genetics influence an individual's strength?

Genetics can determine tissue anatomy, atrophy rates, development of hypertrophy, physical capacity, and healing and remodeling.

How does lifestyle impact age-related decreases in muscle function?

While changes in muscle function are age-related, the amount of decreased strength is a function of training and regular exercise.

How does nutrition affect strength?

Nutrition is an individual difference that can affect strength.

How does pain affect the assessment of muscle strength?

Pain invalidates the assessment of strength if the person is unable to provide a maximal voluntary contraction.

Why is cognitive status important for muscle strength assessment?

For muscle strength assessment (MMT), individuals must be able to understand directions, plan and execute motor action, and pay attention to all factors involved.

How does dementia affect muscle strength assessment?

Dementia causes cognitive impairments that can affect muscle strength assessment.

How do intellectual ability issues affect muscle strength assessment?

Intellectual ability issues can impact understanding directions, thereby affecting muscle strength assessment.

How does aphasia affect muscle strength assessment?

Aphasia, a language impairment, can affect understanding directions for muscle strength assessment.

How does apraxia affect muscle strength assessment?

Apraxia, a motor planning problem, can affect the ability to plan and execute motor actions for muscle strength assessment.

Why might children require special consideration during muscle strength assessment?

Children's developing cognitive status means they might have difficulty understanding directions, planning, and executing motor actions, requiring special consideration for accurate muscle strength assessment.

What psychological/psychosocial factors can influence strength assessment?

Psychological/Psychosocial factors include motivation, fear, and anxiety related to pain.

How does motivation influence strength assessment?

Motivation is a psychological factor that relates to accuracy in muscle testing.

How does fear influence strength assessment?

Fear is a psychological factor that can influence muscle strength assessment.

How does anxiety related to pain influence strength assessment?

Anxiety related to pain is a psychological

How can lack of maximum voluntary effort influence strength assessment?

Lack of maximum voluntary effort (e.g., due to perceived benefits or depression) is a psychological factor that can influence muscle strength assessment.

What environmental factors can affect strength?

Environmental factors such as noise distraction, temperature, and postural requirements for a task can affect strength.

How does temperature affect muscle strength?

Cold temperatures generally lead to less strength due to reduced conduction velocity and less elasticity of collagen and passive structures; muscle functions are most efficient at around 101 degrees Fahrenheit.

What are the muscular factors that influence strength?

Muscular factors include contractility, excitability, elasticity, and recruitment.

Define muscle 'contractility'.

Contractility is the ability of a muscle to produce tension between the ends of two bones to exert a pull, as when a muscle contracts.

Define muscle 'excitability'.

Excitability is the ability of the muscle to respond to stimuli and transmit impulses.

Define muscle 'elasticity'.

Elasticity is the ability of a muscle to recoil from a distended stretch.

How does 'recruitment' affect muscle strength?

The more motor units recruited, the stronger the muscle action.

What is a 'motor unit'?

A motor unit is a single motor neuron and all of the muscle fibers it innervates (smaller muscles, motor units, have fewer fibers… which increases neural control and precision).

What is 'wave summation' in muscle contraction?

Wave summation is the process of recruiting more motor units to produce a multiple motor unit summation, which becomes greater until a smooth, sustained contraction occurs.

What is the purpose of 'asynchronous motor unit contraction'?

Asynchronous motor unit contraction ensures every motor unit is not recruited at the same time, reducing fatigue while enabling smooth movement to occur.

What is the initial event in muscle fiber contraction, according to the Sliding Filament Theory?

A muscle fiber is stimulated.

What is released when a muscle fiber is stimulated in the Sliding Filament Theory?

Calcium.

How does calcium facilitate muscle contraction in the Sliding Filament Theory?

Calcium causes the actin myofilament to slide to the center of the sarcomere through myosin cross-bridging.

What is the result of actin myofilaments sliding according to the Sliding Filament Theory?

Contraction of the muscle fiber.

In what manner do single cell contractions occur according to the Sliding Filament Theory?

In an all-or-none manner.

What are the main types of muscle fibers?

The main types of muscle fibers are Type I, Type IIB, and Type IIA (each motor unit will only have one type of fiber).

Describe Type I muscle fibers.

Type I muscle fibers are generally involved in maintaining posture against gravity and are typically located more deeply and medially.

Describe Type IIB muscle fibers.

Type IIB muscle fibers are fast-twitch glycolytic (anaerobic); they are recruited to produce powerful contractions with sharp bursts of energy; fatigue easily.

Describe Type IIA muscle fibers.

Type IIA muscle fibers are fast-twitch oxidative glycolytic; they participate in both aerobic and anaerobic muscle activities.

What is the active component of a muscle?

The muscle belly.

What is the general term for the passive components of a muscle?

Connective tissue.

What is the epimysium?

Connective tissue that surrounds the entire muscle.

What is the perimysium?

Connective tissue that surrounds fascicles (bundles of muscle fibers).

What is the endomysium?

Connective tissue that surrounds individual muscle fibers.

In addition to the epimysium, perimysium, and endomysium, what other structures are considered passive connective tissues in a muscle?

Tendons, aponeurosis, and fascia.

What structures make up the Series Elastic Component (SEC) of a muscle?

Tendons.

What structures make up the Parallel Elastic Component (PEC) of a muscle?

Sarcolemma, epimysium, perimysium, and endomysium.

What is one function of the Series Elastic and Parallel Elastic Components (SEC & PEC)?

They prevent overstretching of the muscle.

What is another function of the Series Elastic and Parallel Elastic Components (SEC & PEC)?

They ensure contractile elements return to their resting length after a contraction.

What is a third function of the Series Elastic and Parallel Elastic Components (SEC & PEC)?

They protect contractile elements from external forces.

What is passive muscle tension?

Passive muscle tension is generated when the passive components (connective tissues) of the muscle are stretched.

When does a muscle generate the greatest force based on its 'angle of insertion'?

The greatest generation of force occurs when a muscle's fibers are perpendicular to the bone at its angle of insertion.

How does the 'angle of pull' affect force production?

Force production decreases at the extreme outer and inner ranges of motion due to the angle of pull.

What is a concentric muscle contraction?

A concentric contraction occurs when the internal force produced by the muscle is greater than the external force, resulting in the shortening of the muscle.

What is an eccentric muscle contraction?

An eccentric contraction occurs when the internal force is less than the external force, causing the muscle to lengthen (often moving in the direction of gravity).

What are some characteristics of eccentric muscle contractions?

Eccentric contractions are more efficient, use less oxygen, decelerate the motion of a joint, and allow for controlled movement.

What is an isometric muscle contraction?

An isometric contraction occurs when muscles act in a restraining or holding action, with no change in muscle length.

At what muscle length is maximal force production possible?

Maximal force is possible at or near the resting muscle length because the maximal number of cross-bridges can be formed.

What is active insufficiency?

Active insufficiency occurs when a multi-joint muscle is unable to produce enough tension to shorten and complete full active range of motion (AROM) in both joints simultaneously.

What is passive insufficiency?

Passive insufficiency occurs when the antagonist muscle cannot be elongated any further without potential damage.