Biomechanics & Body Movement Analysis Flashcards

Which type of lever is present at the ankle joint during plantar flexion (gastrocnemius lifting the heel)?

Answer: Second-class lever

The ankle in plantar flexion is a second-class lever because the load (body weight at the ball of the foot) lies between the fulcrum (metatarsophalangeal joints) and the effort (calf muscles at the calcaneus).

When analyzing gait, which plane primarily describes the forward progression of the body?

Answer: Sagittal plane

The sagittal plane divides the body into left and right halves and contains the flexion/extension movements that drive forward locomotion.

A patient demonstrates excessive lateral trunk lean toward the stance limb during walking. Which muscle weakness is most likely responsible?

Answer: Gluteus medius

Weakness of the gluteus medius causes a Trendelenburg gait where the trunk leans toward the weak side to keep the center of mass over the support limb.

The term 'valgus' at the knee describes which positional deviation?

Answer: Distal segment angled medially (knock-kneed)

Valgus means the distal bone angles toward the midline, producing a knock-kneed appearance where the knees converge medially.

Which concept in biomechanics describes the resistance of an object to a change in its rotational motion?

Answer: Moment of inertia

Moment of inertia quantifies how mass distribution relative to the axis of rotation resists angular acceleration or deceleration.

During a squat, which joint action occurs at the hip during the descent phase?

Answer: Flexion with external rotation

Hip flexion combined with slight external rotation and abduction is the typical pattern during a controlled squat descent to allow acetabular clearance.

Which term describes the tendency of collagenous tissue to gradually deform under a constant load over time?

Answer: Creep

Creep is the time-dependent deformation of viscoelastic tissue (such as ligament or tendon) when subjected to a sustained load.