What are the three requirements for successful locomotion?

* Progression: producess and coordinates rythmic patterns of muscle activation in the legs  and trunk to succeffully move the body, also requires the ability to initiat and terminate locomotion as well as guide to points (p.316).                         

* Postural Control: reflects the need to establish and maintain an appropriate posture for locomotionand the demand for dynamic stablity in the moving body.        

* Adaptation: enviroments require that gait patterns be adapted on order to avoid obsticals, negotiate uneven terrain, and change speed and direction. 

Know the different phases and events within the gait cycle and the proportions of time spent in each phase.

* Stance: initial contact, the loading response (together taking up about 10% of the step cycle), midstance, terminal stance (about 40% of the stance phase, which is in single support) preswing (that  last 10% of stance, in double support). Stance = 60% of adult cycle. (p.317)

* Swing: initial swing, midswing, terminal swing. Swing = 40% of adult gait cycle.

See Picture Page 317 (Figure 12.1)

How do step parameters change when walking velocity increases?

What determines metabolic cost in walking?

* Generation of propulsive forces by the gastrocnemius makes up about half of the metabolic cost of walking.

What’s the difference between the active push-off and controlled roll-off theories of gait control?

Active Push-off theory:Hypothisizees that thhe energy generated by the plantoar flexor group is fransferred to the trunk to provide support and forward progression. The hip extensors are also recognized as a source of both balance and propulsion 

     During stance the hip extensors give the body a "push form behind" and also contribute to controlling the movement of the head, arms, and trunk preventing stance collapse. (p. 323)

Controlled roll-off theory: Describeds forward progression during single-leg stance as a controlled fall. The primary action of the ankle plantor flexors during the controlled roll-off is to decelerate tibia rotation and prevent knee flexion as the body rotates over the stance leg

     Forward progression is accomplished passivly, not activley, b/c the body moves forward as a result of momentum and inertia

Kinetics

*The dominant forces at a joint do not necessarily mirror the movements of the joint

•The force parameters associated with the normal gait pattern are less stereotyped than the kinematic parameters

•Bipedal gait is characterized by a net extensor moment

•The net extensor moment is generated with a range of different strategies

•Flexibility in how torques are generated is important to controlling balance during gait

What is the cerebellum’s and basal ganglia’s role in gait?

What role does sensory information play in gait control and what happens when sensory information is absent?

* Information from all of the senses is important for controlling locomotion

• When all sensory information is taken away, stepping patterns tend to be very slow and stereotyped

• The animal can neither maintain balance nor modify its stepping patterns to make gait truly functional

* Spinal reflexes are appropriately integrated into different phases of the step cycle to remain functionally adaptive

•    The same outcome occurs in the integration of compensatory automatic postural adjustments into the step cycle

•    Platform perturbation studies have shown that automatic postural responses are incorporated appropriately into the different phases of the step cycle

What roles does vision play in the control of locomotion?

*Vision has three primary roles during locomotion:
1. Detectwhethersurfaceaffordslocomotion

2. Steeraroundobstacles,throughapertures

3. Maintainposturalcontrol
•    Functions 1 and 2 seem to be controlled in central field of view (radial optic flow)
•    Function 3 seems to be controlled in the periphery (lamellar optic flow)
•    Vision used proactively & retroactively (p.334)

What does Rieser’s work tell us about the perceptual-motor organization of locomotion?

* The perceptual-motor organization of locomotion is
recalibrated with experience,  Rieser et al. (1995)

How does somatosensory information contribute to the stance to swing phase transition?

* Contributes to the appropriate stepping frequency.

     For example: the duration of the step cycle is significantly longer in cats that have undergone deafferentation than in a chronic spinalized cat without deafferentation

* Apears to play a role in normal locomotion, with position of the ipsilateral hip joint contributing to the onset of the swing phase.

How is vestibular information used during the control of locomotion?