Mechanics of Walking

• Author: Charles E. Turnbow
• Pages: 117-155

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CHAPTER 4

Mechanics of Walking

§400 Introduction

§410 Human Walking

§411 Bipedal Motion

§412 Cyclic Pattern of Movement

Illustration: Cyclic Pattern of Movement

§413 Ground Reaction Forces

§413.1 Traction Demand and Utilized Coefficient of Friction

§414 Typical Questions and Answers on Normal Walking Forces Generated During

Normal Stride

§415 Phases of the Stride

Illustration: Phases of Walking

§416 Stair Gait

Illustration: Phases of the Stride

§420 Gait Analysis

Illustration: Posterior View of Ankle on Heel Contact

§421 Medial or Lateral Body Shifting

Figure 4.1: Lateral Movement of the Foot During the Stride

Figure 4.2: Stringer Elevated Above the Plane of Tread

§422 Speed of Walking

§423 Angle of Impact

Figure 4.3: Moments of Force During Heel Strike

§424 The Effect of Aging and Physical Impairment

§425 Arm Function

§430 Experiments and Ergonomic Studies on Slipping

§440 Walking Surfaces

§441 Level Surfaces

Picture: Uneven Stepping Stones

§442 Ramps

Table: Static Coefficient of Friction for Level Surfaces and Various Gradients

§442.1 Side Slopes

§443 Stairways

Picture: No Slip Stripes

§444 Curbs and Risers

§445 Wheel Stops

Figure 4.4: Tire Stop and Standard Parking Stall Dimensions

Picture: Badly Placed Tire Stop

Picture: Asphalt in Bad Repair

Figure 4.5: Handicapped Parking Space

§446 Speed Bumps

Picture: Speed Bumps With Solid Painting

Picture: Proper Marking and Delineation

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 MECHANICS OF WALKING

§447 Rough and Uneven Work Surfaces

§450 Balance and Perception

§451 Cone of Vision

§452 Visual Cues or Flags

Figure 4.6: Contrasts Against Background

Figure 4.7: NIOSH Contrast Visibility Chart

§452.1 Color Contrast

Picture: Lack of Contrast

§452.2 Lighting and Illumination

§453 Determining Visibility or Visual Acuity

§453.1 Glare

§454 Spatial Vision and Pattern Perception

§454.1 Defining an Object

§454.2 Visual Acuity and Contrast Sensitivity Function (CSF)

§454.3 Primary Factors That Determine the Visibility of Objects

§454.4 Orientation Edges

§455 Distractions

Picture: Floor Pattern Hiding Riser

Picture: Riser Hidden By Tile Pattern and Color

§455.1 Orientation Edges

§455.2 Geometric Patterns

§455.3 Vehicular and Pedestrian Traffic

§455.4 Point-of-Purchase Displays

§460 Checklist: Evaluating a Walkway

Picture: Repaired Walkway

Picture: Uplifting Tree Roots

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§400 SLIP AND FALL PRACTICE 

§400 Introduction

The slip and fall practitioner should understand the mechan-

ics of walking and the forces that are generated during the

stride. Scientists have been measuring and studying these

forces for over half a century. Herbert Elftman and his

coworkers at New York University were early pioneers in

the development of the scientific concepts of human loco-

motion, writing a series of papers widely published from

1934 to 1939 on pressure distribution during the stride and

the forces generated by various muscles.

Post-war studies used improved instrumentation to measure

ground reaction forces, cadence and other parameters con-

cerned with gait analysis. Some of the most extensive work

was done at the University of California in the late 1940s.

In 1948, J.P. Frankel and B. Bressler presented a paper to

the American Society of Mechanical Engineers (ASME)

in which they reported the results of their research into the

Forces and Movements of the Leg During Walking. This

work was part of a grant by the National Research Council to

establish the groundwork for a project entitled Fundamental

Studies of Human Locomotion. In this country, the study

of human locomotion was continued under the guidance

of Verne Inman, M.D., and Henry Ralson, Ph.D., at the

Biomechanics Laboratory at the University of California

at San Francisco and Berkeley. A compendium of their

work was first published in 1981 under the title, Human

Walking, by Williams & Wilkins. The work is now in its

second edition by Rose and Gamble (1993). More recent

research in both ground reaction forces and traction demand

has been published in an American Society for Testing and

Material STP 1424, Metrology of Pedestrian Locomotion

and Slip Resistance (2002). Other publications which will

be helpful to a more technical understanding of human

walking and behavioral sciences associated with pedestrian

safety are: Introduction to Ergonomics by R. S. Bridger,

Taylor & Francis (2003); Measuring Slipperiness, Chang

and Courtney, editors, Taylor & Francis (2003); Pedestrian

Slip Resistance, 2nd Edition, Wm. English, Inc. (2003);

Perception, Sekuler and Blake, 3rd Edition, McGraw-Hill

(1994); Essential Clinical Anatomy, 2nd Edition, K. Moore

and A. Agur, Lippencott-Williams & Wilson (2002); Joint

Structure and Function, 4th Edition, P. Levangie and C.

Norkin, F.A. Davis Co. (2005).

§410 Human Walking

Studies in ambulation were first extensively conducted in

the nineteenth century. As science and technology increase

the understanding of human locomotion and the effect

to the physical world on the pedestrian’s ability to move

around the earth, many of the earlier notions of motion

and perception have been revised. The causes and preven-

tion of pedestrian fall accidents are closely related to our

understanding of how people walk and perceive the world

around them.

§411 Bipedal Motion

Quadruped animals gain stability walking on four feet,

because in most cases there are three feet on the ground at

all times. Such a walking mode requires little training and

comes naturally even to human infants. Bipedal human

walking is a learned activity that requires a combination of

instinct and learning. Each individual walks a little differ-

ently, but most of the ground reaction forces, cadence and

balance, and perception ability are in a general range that

can be studied and quantified.

§412 Cyclic Pattern of Movement

Walking is a nonspecific term that generally refers to a cyclic

pattern of movement that is repeated step after step, over and

over. Because of this cyclic pattern, most of the mechanics of

walking can be studied and described by looking at a single

cycle. Walking is the process in which the erect human body

is supported on one leg then the other. The center of body

mass moves forward and in doing so passes over the support-

ing leg, as the opposite leg starts to swing forward in prepa-

ration for repeating the cycle. As the foot leaves the ground

and swings forward, the support of the body transfers to the

opposing leg. The support is transferred back to the swinging

leg when it impacts the walkway surface and the body weight

shifts forward to be centered over the leg again. During this

phase of the stride, both feet are in contact with the ground;

during the rest of the stride only one foot is in contact at any

given time. Olney characterizes this as double support time

when both feet are on the ground during one gait cycle. The

percentage of the gait cycle spent in double support may

be increased in the elderly persons and those with balance

problems. The cycle percentage of double support decreases

as the speed of walking increases. (Olney, S., Joint Structure

and Function, 4th Ed., P. Levangie and C. Norkin, Editors.

F.A. Davis Co. (Chapter 4, Gait, page 522) (2005).)