Introduction
Human gait can be defined as the translatory progression of a human body as a whole produced by co-ordinated rotatory movements of the body segments,also known as human locomotion.
In human locomotion, the reader is given opportunity to discover how individual joints and muscles function in an integrated manner both to maintain upright posture and to produce motion of the body as a whole.Knowledge of the kinematics and kinetics of normal ambulation provides the reader with a foundation for analyzing,identifying and correcting abnormalities in gait.
Major tasks of gait
To understand gait, first let us identify the fundamental purposes of gait.Winter proposed the following five main tasks for walking gait:
- Maintenance of support of the head,arms,and the trunk ,that is preventing collapse of the lower limb.
- Maintenance of upright posture and balance of the body.
- Control of the foot trajectory to achieve safe ground clearance and a gentle heel or toe landing.
- Generation of mechanical energy to maintain the present forward velocity or to increase the forward velocity.
- Absorption of mechanical energy for shock absorption and stability or to decrease the forward velocity of the body.
Maintaining balance and stability is clearly important during ambulation, and there is an increasing body of literature on what might be called sub-tasks of gait that are potentially destabilizing.This include gait initiation and termination,stair climbing,turning,obstacle crossing,and negotiating a raised surface.
Phases of gait cycle
Gait has been divided into number of segments that make it possible to describe,understand and analyze the events that are occuring.A gait cycle spans two succesive events of the same limb,usually initial contact or heel strike of the lower extremity with the supporting surface.During one gait cycle,each extremity passes through two major phases: a stance phase when some part of the foot is in contact with the floor,which makes up 60% of the gait cycle and a swing phase which makes up the remaining 40% of the gait cycle.There are two periods of double support occuring between the time one limb makes a heel strike and the other foot leaves the floor at toe-off.
At normal walking speed,each period of double support occupies about 11% of the gait cycle,which makes a total of approximately 22% of full cycle.The body is thus supported by only one limb for nearly 80% of gait cycle.The approximate value of 10% for each double-support phase is usually assigned to each of the two double-support periods.
Stance phase id divided into subphases by a number of events that mark the start and end of the subphases.The gait cycle is divided into percentiles that will be used to clarify events and phases.Values for normal walking is shown in the figure below:
Rancho-Los-Amigos(RLA) system of gait cycle
STANCE PHASE
- Heel strike (0%)the leg has to accept the weight of the body.
- Loading response(10%)it is the first 10% of the gait cycle.Loading response ends once the contralateral foot lifts off the ground.Now,we are in single limb support.
- Mid-Stance(30%)After loading response until the point of heel-off,we are in a mid-stance phase.Midstance is a point where the body weight of the body is directly over the supporting lower extremity.
- Terminal Stance(30%-50%)The heel off of the right foot starts to lift (heel-off),while the contralateral leg has initial contact with the ground.
- Pre-Swing(50%-60%)Where the contralateral leg is proceeding to make full contact with the ground;the right foot lifts off further.
SWING PHASE
- Initial Swing(60%-70%)this phase starts from toe off until the feet are adjacent.
- Mid Swing (73%-87%)in this phase tibia is vertical.
- Terminal Swing(87%-100%)this phase ends with heel-strike of the right or dominant leg.
Gait Terminologies
Temporal variables includes:
- Stance time
- Single-limb support time
- Double-limb support time
- Swing time
- Stride time
- Step time
Distance variables includes:
- Stride length
- Step length
- Step width
- Dergree of toe-out
Combined parameters icludes:
- Cadence
- Velocity
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Note:Each variable may be affected by such factors such as age,sex,height,size and shape of bony components,distribution of mass in body segments,joint mobility,muscle strength,type of clothing and footgear,habit,and psychological status.
Description of temporal parameters:
Stance time is the amount of time that elapses during the stance phase of one extremity in a gait cycle.
Single-support time is the amount of time that elapses during the period of when only one extremity is on the supporting surface in a gait cycle.
Double-support time is the amount of time spent with both the feet on the ground during one gait cycle.The percentage of time spent in double support may be increased in the elderly persons and in those with balance disorders.The percentage of time in double support decreases as the speed of walking increases.
Stride duration or time refers to the amount of time it takes to accomplish one stride.Stride time and gait cycle duration are synonymous.One stride, for a normal adult,lasts approx 1 seconds.
Step duration or time refers to the amount of time spent during a single step.Measurement usually is expressed as seconds per step.Measurement usually is expressed as seconds per step.When there is weakness or pain in an extremity, step duration may be decreased on the affected side and increased on the unaffected (stronger) or less painful side.
Description of distance variable:
Stride length is the linear distance between two succesive events that are accomplished by the same lower extremity during gait.
In general,stride length is determined by measuring the linear distance from the point of one heel strike of one lower extremity to the point of the next heel strike of the same extremity.
Step length is the linear distance between two successive points of contact of opposite extremities.It is usually measured from the heel strike of one extremity to the heel strike of the opposite extremity.
Step width may be found by measuring the linear distance between the midpoint of the heel of one foot and the same point on the other foot.
Degree of toe-out represents the angle of foot placement and may be found by measuring the angle formed by each foot's line of progression and a line intersecting the centre of the heel of the second toe.
Description of Combined parameters:
Cadence is the number of steps taken by a person per unit time.Cadence may be measured as the number of steps per second or per minute.
Walking speed is the rate of linear forward motion of the body,which is measured in meters or centimeters per-second,per - minute,or miles per hour.
Conlusion
Hello readers, hope this content is useful for you all,specially the students.All the basic details of gait/gait cycle is mentioned in this post,hope it is be helpful for you.
Don't forget to share it with your friends and if you have any queries or questions please mention it in the comments section.
Stay safe stay healthy
Thank you
The Healer Physio Team.
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