Human Anatomy & Biomechanics Flashcards

A muscle contraction in which force is produced without any change in muscle length (e.g., holding a tool in a fixed position) is classified as:

Answer: Isometric

Isometric contractions occur when a muscle exerts force while its length remains constant; prolonged static holds contribute significantly to muscle fatigue in ergonomic tasks.

The nucleus pulposus is the hydrated, gel-like core found within which spinal structure?

Answer: Intervertebral disc

The nucleus pulposus is the central gelatinous material of the intervertebral disc that distributes compressive loads and provides flexibility; it loses hydration with age and repetitive loading.

In biomechanics, the 'moment arm' is defined as:

Answer: The perpendicular distance from the axis of rotation to the line of force application

The moment arm is the perpendicular distance from the pivot (joint) axis to the line of action of the applied force, directly determining the torque generated.

The NIOSH Lifting Equation's Recommended Weight Limit (RWL) is calculated by multiplying a load constant by task multipliers that include:

Answer: Horizontal distance, vertical height, travel distance, asymmetry angle, frequency, and coupling quality

The NIOSH Lifting Equation uses six multipliers (horizontal, vertical, distance, asymmetry, frequency, coupling) applied to a 51-lb load constant to compute the RWL.

Cumulative trauma disorders (CTDs) of the upper extremity are primarily caused by:

Answer: Repeated low-level mechanical stress accumulating over time

CTDs result from the accumulation of microtrauma from repeated exposure to risk factors such as force, repetition, and awkward posture over extended periods.

Forearm pronation results in the palm facing:

Answer: Downward (posteriorly in anatomical position)

Pronation rotates the radius over the ulna so the palm faces downward (posteriorly), the opposite of supination; sustained pronation during keyboard use is an ergonomic risk factor.

The four muscles of the rotator cuff attach primarily to which bone?

Answer: Humerus (greater and lesser tubercles)

The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) originate on the scapula and insert onto the greater and lesser tubercles of the humerus to stabilize the glenohumeral joint.