Lower Limb - Biomechanics of Walking Flashcards
What is the sole purpose of walking (and running)
to transport the body safely and efficiently over the ground, regardless of the nature of the environment around the body
What are the 5 main functions of performed during each stride period?
- Maintenance of support of the upper body during stance (period when foot is on the ground)
- Maintenance of upright posture and balance of the total body
- Control of the foot trajectory to achieve safe ground clearance and a gentle heel or toe landing
- generation of mechanical energy to maintain the present forward velocity or to increase the forward velocity
- Absorption of mechanical energy for the shock absorption and stability or to decrease the forward velocity of the body
What is the definition for stride length?
Horizontal Distance from the Initial Contact of the foot to the next Initial Contact of the same foot.
What is the formula for velocity using stride length
What are the phases of the step cycle
How does vertical displacement of the center of mass during walking relate to conservation of energy?
- vertical displacement of the CofM is directly out of phase with the horizontal velocity of the CoM. This allows for a major conservation of energy within the trunk segment. This is due to the fact that the body is acting like an inverted pendulum over the single stance limb as it vaults up and over the limb
-First half of the stance phase, kinetic energy is converted into
gravitational potential energy. Second half of the stance phase, the opposite occurs. Because the gravitational potential energy and kinetic energy fluctuations are nearly equal in magnitude and 180° out of phase in walking, humans can exchange substantial mechanical energy
What are the ground reaction forces while walking?
What are the patterns of the Joints while walking?
What are the joint angles and torques for legs joints during walking
What is the relationship between joint torque and joint angle?
If joint torque and joint angle are in opposite the body is absorbing energy
What is the support moment?
An overall extensor moment required during stance to keep the body upright
Ms = Mh + Mk + Ma
If the support moment was to go negative, it would indicate the person is falling.
Indicate that limb is pushing away from the ground. correlates extremely well with vertical ground reaction force.
What is the Hip-Knee trade off in support moment?
Hip and knee joint show a lot of variability in moment, but when added together where almost the same. This shows redundancy in which muscles can be used.
Force Plate: fore triaxial transducers
Force Plate: Pedestal
How is the centre of pressure and centre of mass trajectories related duinrg walking?
- The Centre of Mass of the body never travels within the base of support, but only just medial to the inside of the foot.
- The movement of the CoM is such that while it is behind the foot, the medial-lateral trajectory is towards the stance foot, but as soon as it passes in front of the foot, it is towards the projected placement of the swing foot
It should be noted that the CoM is decelerating while it is behind the stance foot, and accelerating as it moves in front of the stance foot.
Power generation during the Walking Cycle
What are the characteristic of power generation of the ankle during walking?
Between about 5% and 40% of the step cycle, the ankle is undergoing dorsiflexion (as the leg rotates forward over the foot), with a fairly substantial plantarflexion moment being generated. This leads to
the A1 power phase, which is energy absorption.
Between 35% and 40% of the step, the heel starts lifting off the floor, and active and rapid plantarflexion starts to occur. The product of the moment and the
rotational acceleration are in the same direction and large and thus a large energy generation phase occurs (positive power). This continues to toe off.
