Lec 3- Gait and Motor Activation

Question 1

Muscular Activation in Gait Definitions

Answer 1

Isotonic: length changes in muscle
Concentric: isotonic contraction where muscle is shortening (generation of speed, force)
Eccentric: isotonic contraction where muscle is lengthening (controlling joint), shock absorption, deceleration, control
Reciprocal Inhibition: allows joint to freely move w/o antagonist activating
Co-Activation: simultaneous contraction of agonist and antagonist muscle groups work to stabilize the joint
Muscular Synergies: groups of muscles across joints that work together to perform activity

Question 2

Why is walking efficient and smooth?

Answer 2

-Muscular activity is delivered at spinal cord level during routine walking
-Genetic blueprint and years of training
-Finely tunes on and off muscular activation

Question 3

Reciprocal Inhibition

Answer 3

-is governed at the SC level
-is a system created by a stimulus activation (activation and reciprocal inhibition)
-occurs across muscle groups in both limbs
-allows for on and off cycle of muscle activation
-allows flexibility
-is a mechanism to govern motor function

Question 4

Reciprocal Inhibition occurs with activation of…

Answer 4

muscular contraction (prevents agonist and antagonist activation)

Question 5

An example of reciprocal inhibition

Answer 5

Terminal Swing
Ankle: Anterior Tibialis is activated and Gastroc/Soleus is not activated
-allows ankle DF not to be impeded
-allows for optimal joint function thru DF

Question 6

An example of muscular co-activation

Answer 6

Terminal Stance
Knee: Quadriceps are concentrically activating and hamstrings are eccentrically
-controlling knee extension
-purpose is to control, decelerate down knee extensor activity
-absorb ground shock

Question 7

Neurobiology of Gait: CPGs

Answer 7

-brain to spinal cord
-SC coordinates on and off timing of motor activity during walking
-controlled by CPGs in SC (control limb segments, ipsilaterally and contralaterally)

Question 8

How does the CPG work?

Answer 8

Rhythm Network: method of activating muscle groups or motor pools of flexors then extensors
-combination of sensory/feedback (touch, pressure from environment & forces within muscle) to provide feedback to pattern formation and provide motor activity
-sensory input adjusts rhythm and walking pattern

Question 9

Muscular Activation in Walking

Answer 9

-organized by swing phase (flexors) and stance phase (extensors)
-force generation emerges from stance phase
-timing of muscle groups is rhythmical and speeds up/slows down based on indv. pace
-similar across human species

Question 10

Initial Contact

Answer 10

Hip: glute max and add. magnus active to prep for LR
Knee: Quad extend knee, HS contact to counteract contact torque
Ankle: TA eccentric control and pre tibial muscles

Question 11

Loading Response

Answer 11

Hip: glute max (low fibers), add. magnus, & HS are activated to counteract flexor torque. TFL, glute med., and glute min., and glute max (upper fibers) stabilize frontal plane
Knee: Quad eccentric activity (knee flexed absorbs shock)
Ankle: EHL, EDL, TA eccentrically contract. TA peaks activity (eccentric). TP stabilizes t/o stance, gastroc-soleus activates late loading response.

Question 12

Midstance (SLS)

Answer 12

Hip: No sagittal plane muscle activity except glute max. (upper fibers), glute med. stabilizes frontal plane, TFL co-activates for stability
Knee: Quads stabilize dynamic knee stability up until midstance eccentric
Ankle: Gastroc-soleus restrains tibia for forward progression. Gastroc-soleus eccentrically control forward progression of tibia

Question 13

Where does gait break most often?

Answer 13

Loading Response & Midstance
-LR: quads eccentrically control for shock absorption
-Midstance: gastroc-soleus controls tibia advancement over fixed foot

Question 14

Midstance Frontal Plane Activation

Answer 14

-Glute med. provides frontal plane stability at hip
-TFL co-activates for stability across hip and knee

Question 15

Terminal Stance (Trailing Limb)

Answer 15

Hip: anterior TFL still on (from LR)
Knee: No quads activation. Bicep fem. activation to prevent knee extension
Ankle: Gastroc-soleus peaks to prevent tibial collapse (provides propulsion), TP FL & FB stabilize

Question 16

Pre-Swing

Answer 16

Hip: Add. longus and rectus fem. to flex femur
Knee: Gracilis prep for knee flexion
Ankle: Gatroc-soleus ceases activity early in pre-swing

Question 17

Initial Swing

Answer 17

Hip: Iliacus starts and stops, sartorius and gracillis peak. HS come in late mid-swing (co-activate at hip to decelerate)
Knee: Bicep fem short head, sartorius, and gracillis peak to flex knee
Ankle: EDL and EDL peak active to initiate DF. TA continues from mid-swing

Question 18

Mid Swing…

Answer 18

Carries momentum from terminal stance and initial swing
Hip: carries on motor activity from initial swing w/ gracilis carrying momentum
Knee: carries knee extension, thru momentum HS begin to decelerate
Ankle: Pre-tibial active and carry momentum

Question 19

Terminal Swing

Answer 19

Hip: HS peak at activity, Hip Stabilizers (lower fibers of glute max, add. magnus to stabilize hip)
Knee: Quads. concentrically activating, in late terminal swing HS activate to reduce quad acceleration
Ankle: EDL, EHL, and TA concentric active

Question 20

Highest muscle forces

Answer 20

-IC: hip extensor and knee flexor for eccentric control of IC
-LR: hip abductors to stabilize hip
-Terminal Stance: Ankle PF for propulsion