Lecture on Kinesiology of Muscle Force and Impact on the Spine

Introduction

• Focus on muscle force and its impact on the spine.
• Importance of correct posture.
• Encourages self-awareness of posture.

Neck and Head Position

• Neutral Position:
  • Head in the middle/neutral position.
  • Classic first-class lever system.
  • Minimal muscle force required from neck extensors.
• 45-Degree Flexion:
  • Common position when using cell phones.
  • Longer moment arm compared to neutral position.
  • Requires more muscle force from neck extensors.
  • Increased stress on C-spine.
  • Risk of disc herniation or rupture.

Effects of Prolonged Flexion

• Greater gravity effect and more strength required from erector spinae.
• Poor bilateral activation of sternocleidomastoid (SCM).
• Difficulty in chewing and swallowing due to lack of chin tuck movement.

Recommendations

• Maintain upright position.
• Take frequent breaks.
• Stretch neck muscles (flexion and extension).

Trunk Position and Lifting

• Carrying Heavy Boxes:
  • Larger boxes have longer moment arms.
  • Heavier items should be kept closer to the body.
  • Avoid locking elbows and shoulders; lean backward instead.
  • Leaning backward increases stress on L-spine.
• Bending Over:
  • Increases moment arm and stress on erector spinae.
  • Common stress points: L4 and L5 vertebrae.

Posture While Using Devices

• Using Laptops:
  • Kyphosis and posterior pelvic tilt.
  • Cervical lordosis to gaze at the screen.
  • Pelvic tilt to one side increases stress on lumbar and C-spine.

Occupational Therapy (OT) Role

• Responsibility to correct poor posture and improve occupational performance.
• Further discussion to follow in the next session.

Conclusion

• Introduction to how posture affects the spine.
• Encouragement to maintain good posture to prevent chronic pain.
• Thank you for attention.