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• Gait cycle• Kinematics and ground reaction forces

– Methods of studying gait– Gait changes with children and ageing

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.

The Gait Cycle:

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

Walking – The Stance Phase

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

Walking – The Swing Phase

GRF while walking

GRF while walking

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 - 180 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)

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

Running – A Gait Cycle

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

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)

Sample gait checklist

Analysis aids: Pressure on bottom of feet

Force Plates – Measurement of ground

reaction forces

Optoelectric system - Vicon

Vicon System:

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

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

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?