Lec 14

Question 1

What characterizes good vs. bad posture and how does each affect energy use?

Answer 1

Good posture: Vertically balanced segments; minimizes rotary effect of gravity.

Bad (fatigue) posture: Zigzag alignment; muscles relax and ligaments bear load → increases rotary effect and strain.

Energy use: Bad posture (fatigue posture) is more economical short term, but causes strain and injury long term.

Question 2

What increases the rotational pull of gravity on the body?

Answer 2

Zigzag alignment of segments

Curved spinal column (AP curves)

Posterior trunk column with forward-projected feet

Anterior chest load (esp. with large breasts in females)

Question 3

What is lordosis and what causes it?

Answer 3

Definition: Excessive inward curvature of the lumbar spine.

Causes: Weak abdominal muscles, anterior pelvic tilt, overtraining in lumbar hyperextension.

Question 4

What is kyphosis and who is it common in?

Answer 4

Definition: Excessive outward curvature of the thoracic spine (hunchback).

Common in: Adolescents (e.g., swimmers doing butterfly stroke) and elderly women (osteoporosis).

Question 5

What is scoliosis and its types?

Answer 5

Definition: Lateral curvature of the spine.

Types:

Structural (congenital)

Non-structural (e.g., leg length discrepancy)

Often occurs in right thoracic and left lumbar regions.

Question 6

Where is the center of mass (COM) relative to the spine and what does this mean for back extensors?

Answer 6

COM is anterior to spinal column, creating a constant forward bending moment.

Back extensors must constantly generate counteracting torque, requiring high muscle activation.

Question 7

What is the relative size of the moment arm for trunk extensors, and why is that important?

Answer 7

Moment arm is small, so back extensors must produce large forces to balance body weight and loads.

Question 8

What increases lumbar spine compression and which positions are best/worst?

Answer 8

Increased by: Forward bending, lifting with poor technique.

Best position: laying on back

Worst position: sitting with fatigued posture

Question 9

What is the flexion-relaxation phenomenon?

Answer 9

When spine is in full flexion, spinal extensors relax, and ligaments bear the flexion load.

Dangerous during lifting—ligaments can’t handle heavy loads alone → injury risk.

Question 10

What is the correct technique for lifting to protect the spine?

Answer 10

Maintain neutral spine.

Use hip and knee flexion.

Keep load close to body.

Avoid full spinal flexion.

Engage abdominals and extensors.