HUBS191 Lecture 11: Musculoskeletal System - Complex Movements (Standing and Gait)

Lecture Objectives

  • Describe the anatomical features of the lower limb that allow standing with minimal energy expenditure.
  • Define the phases of the gait cycle.
  • Understand and describe the sequence of muscle activity during the gait cycle.

Standing

Quadrupedal Standing

  • Base of support involves multiple limbs.
  • Limbs are active at many joints, demanding energy.

Bipedal Standing

  • Small area of contact with the ground (plantar surface of feet).
  • Energy-efficient.
Muscle Roles Recap
  • Agonists: act concentrically (muscle shortens).
  • Antagonists: act eccentrically (muscle lengthens).
  • Stabilizers: act isometrically (muscle length remains constant).
  • Gravity can act as an agonist or antagonist.
Line of Gravity
  • Maintaining a stable, upright stance needs to be energy efficient.
  • This requires anatomical solutions.
  • The line of gravity is posterior to the hip, anterior to the knee, and anterior to the ankle.
Hip
  • Line of gravity is posterior to the joint.
  • 'Pushes' joint into extension.
  • Ligaments are tight, locking the joint.
  • Results in no energy spent.
  • Capsular ligaments:
    • Hip in flexion: lax anteriorly; taut posteriorly.
    • Hip in extension: taut anteriorly; lax posteriorly.
Knee
  • Line of gravity is anterior to the joint.
  • 'Pushes' into extension.
  • Ligaments are tight, locking the joint.
  • Results in no energy spent.
Ankle
  • Line of gravity is anterior to the joint.
  • 'Pushes' into dorsiflexion.
  • The joint is NOT locked.
  • Plantarflexors are needed to stabilize, consuming energy.
Bipedal Standing Summary
  • Unique to humans.
  • Feet form the base of support, but are insufficient alone for balance.
  • Special anatomical features at joints assist balance.
  • Standing is achieved with very little muscular support, mostly at the ankle joint.
True or False Questions
  • The line of gravity falls posterior to the knee (False).
  • Dorsiflexors stabilize the ankle during upright standing (False - Plantarflexors do).
  • The agonists of hip flexion are iliopsoas and rectus femoris (True).

Bipedal Walking

  • Learned movement strategy.
  • Gait is characteristic.
  • Basic pattern = gait cycle.
  • Complex series of movements:
    • Stance phase
    • Swing phase
    • Transition phases (heel strike, toe-off)

The Gait Cycle

  • Complex and dynamic involving many movements and muscles.
  • Focus on flexion and extension, and muscles learned previously.
  • Many phases, but focusing on 6 key parts.
  • Cycle is continuous and in motion.
  • Joints may be in one position but moving into another.
    • Muscle action reflects where the joint needs to end up.
Phases of Gait Cycle
  • Stance Phase: Right Leg & Left Leg
  • Swing Phase: Right Leg & Left Leg
  • Double Stance Phase

Key phases:

  • Early stance (heel strike)
  • Mid stance
  • Late stance (toe off)
  • Early swing
  • Mid swing
  • Late swing
Gait Dynamics
  • For each phase, consider:
    • The position the joint starts in.
    • The position the joint needs to be in for the next phase.
    • What muscle & type of contraction will bring the joint to the next phase.
Early Stance (Heel Strike)
  • Hip: In flexion, moving into extension.
    • Agonists: gluteus maximus & hamstrings.
  • Knee: In extension (locked for stability).
    • Stabilizers: quadriceps femoris & hamstrings & gastrocnemius.
  • Ankle: In dorsiflexion, moving into plantarflexion.
    • Agonist: triceps surae.
    • Antagonist: tibialis anterior (controls rate of foot drop).
Mid Stance
  • Hip: Continuing to move into extension.
    • Agonists: gluteus maximus & hamstrings.
  • Knee: Moving from extension into slight flexion.
    • Agonists: hamstrings & gastrocnemius.
  • Ankle: Continuing to move into plantarflexion.
    • Agonist: triceps surae.
Late Stance (Toe Off)
  • Hip: In extension.
    • Agonists: gluteus maximus & hamstrings.
  • Knee: In extension due to body position.
    • Hamstrings & gastrocnemius are contracting, ready for the next movement.
  • Ankle: In full plantarflexion.
    • Agonist: triceps surae (strong for propulsion).
Early Swing
  • Hip: In extension, moving into flexion.
    • Agonists: iliopsoas & rectus femoris.
    • Antagonists: gluteus maximus & hamstrings (control rate of swing).
  • Knee: In flexion to lift foot from the ground.
    • Agonists: hamstrings & gastrocnemius.
  • Ankle: In dorsiflexion for toe clearance.
    • Agonist: tibialis anterior.
Mid Swing
  • Hip: In flexion.
    • Agonists: iliopsoas & rectus femoris.
    • Antagonists: gluteus maximus & hamstrings (control rate of swing).
  • Knee: In flexion to lift foot from the ground.
    • Agonists: hamstrings & gastrocnemius.
  • Ankle: In dorsiflexion for toe clearance.
    • Agonist: tibialis anterior.
Late Swing
  • Hip: In flexion.
    • Agonists: iliopsoas & rectus femoris.
  • Knee: Moving from flexion into extension to prepare for heel strike.
    • Agonists: quadriceps femoris.
  • Ankle: In dorsiflexion for stable joint position at heel strike.
    • Agonist: tibialis anterior (pulls into dorsiflexion).
    • Stabilizer: triceps surae (keeps ankle stable).

Tips for Learning the Gait Cycle

  • Learn muscle position and action first.
  • Each phase isn’t a snapshot; it’s a movement.
  • How do you get from where the joint was to where it needs to be?
    • What muscles must contract?
    • What type of contraction?
  • Practice walking and thinking about each joint.

Practice Essay Questions

  1. Compare the structure of the ankle to the hip joint, noting differences in bones, muscles, and movement. (3 marks)
  2. The ankle is an important region of the lower limb. Write an essay on the structure and function of the knee, including the following components:
    • Outline the changes in position of the ankle joint throughout both swing and stance phases of the gait cycle, including the roles of muscles. (3 marks)
    • Describe how severe damage to the tibialis anterior would impact the normal gait cycle. (2 marks)