1. Analysis of a continuous skill – walking and running (gait)
Reading assignment:
Jones & Barker, Ch 15; McNeil, Ch 5
Outline
Walking
Gait cycle
Kinematics and ground reaction forces
Running
Methods of studying gait
Gait changes with children and ageing

2. Walking Analysis … the process
A gait cycle consists of “the activities that occur from the point of initial contact of one lower extremity to the point at which the same extremity contacts the ground again”
During one gait cycle, each extremity passes through two phases, a single stance phase and a single swing phase.

3. The Gait Cycle:

5. Components of the Stance Phase
Stance phase comprises 60% of the gait cycle
Heel strike – moment when the heel first strikes the ground
Foot flat – from heel strike to when the full foot is in contact with the ground
Midstance – body weight is directly over the stance leg
Heel off – moment the heel of the stance leg leaves the ground
Toe off – when only the toe of the stance leg is in contact with the ground

6. Walking – The Stance Phase

7. Components of the Swing Phase
Swing phase comprises 40% of the gait cycle
Acceleration – the toe of the stance leg leaves the ground and begins to swing forward
Midswing – the swinging leg is directly beneath the body
Deceleration – the swinging leg continues forward towards knee extension but is slowing down as it travels, stopping just prior to full knee extension and heel contact with the ground

8. Walking – The Swing Phase

10. GRF while walking

11. GRF while walking

15. Range of motion at the joints
Trunk - As left leg moves forward, pelvis rotates clockwise as viewed from above 7 deg
Hip Joint (30 deg flex at HS strike, 180 deg at TO)
Stance - extension, adduction, internal rotation
Swing - flexion/extension, abduction, ext rotation
Knee joint deg at HS, 160 deg at mid-stance
Ankle joint - Neutral at HS, hinges down during support, and plantar flexes at TO . ROM 30 deg
COM displacement +5 cm bilaterally and vertically (Note: Frankel and Nordin state that normal values are + 4 cm bilatgerally and +3 cm vertically)

17. Running Analysis…...
Running is similar to walking BUT, it differs significantly in a number of ways, for example:
No period of “double support”
Float periods (both feet airborne)
Requires greater balance
Requires greater strength
Requires greater ROM at hip, knee, and ankle joints
Involves greater excursion of center of mass
Involves greater ground reaction forces

18. Running – A Gait Cycle

19. Muscle Activity in Running...
Glut. Max. & med. -- active at the beginning of the stance phase (concentrically) and again at the end of the swing phase (eccentrically).
Iliopsoas -- active during a portion of the swing phase (concentrically).
Quadriceps -- 1st 10% of the stance phase (eccentrically) and last 20% of the swing phase (concentrically).
Hamstrings -- initial portion of the swing phase (concentric) and at the end of the swing phase (eccentric).
Plantar flexors (gastrocnemius & soleus) – Mid and latter part of stance phase

20. Methods of Studying Gait
Observational techniques (use checklist, and videotape when possible)(Slide 18)
Quantitative analysis
time-distance measurements (stop watch, footswitches) (Slide 19)
Kinetic techniques (Slide 20)
Kinematic analysis
Videotaping, semi-automated imaging (Slides 21 & 22)
Combined kinematic and kinetic (Slides 20 & 21)

21. Sample gait checklist

22. Analysis aids: Pressure on bottom of feet

23. Force Plates – Measurement of ground reaction forces

27. Optoelectric system - Vicon

28. Vicon System:

29. Gait changes with normal ageing
Generally, they try to improve stability by the following adjustments:
Shorter step and stride lengths
lower walking speeds
greater variation in stride width
wider base of support

30. Gait in children base is wider until 4 yrs
no heel strike until 2 yrs - contact is made with a flat foot
stride length and velocity is less
cadence is greater
reduced knee flexion in stance phase until 2 yrs of age
no reciprocal arm swing until 4 yrs
adult stride length, velocity & cadence are obtained around 15 yrs of age

31. Scientific Method of Problem Solving
Develop (define and delimit) the problem
Formulate the general hypothesis:
Overload training improves strength
(e.g., 3 sets of bp 3 d/w will improve bp strength)
Formulate the specific hypothesis:
If A (general) is true, then B (specific) will be true
(e.g., if the general hyp is true, then posttest > pretest)
Gather , analyze, and interpret the data
If B is true (significant difference), what about A?
If B is not true (no sig diff), what about A?
Discuss the results
Is B without A very unlikely, or are there alternative explanations?