lecture 1 introduction (1).pdf

Gait analysis Gait is the medical term to describe human locomotion or the way that we walk. Interestingly, every individual has a unique gait pattern. A person’s gait can be greatly affected by injury or disease process. By evaluating the gait pattern of an individual, a therapist can determine sp...

Gait analysis Gait is the medical term to describe human locomotion or the way that we walk. Interestingly, every individual has a unique gait pattern. A person’s gait can be greatly affected by injury or disease process. By evaluating the gait pattern of an individual, a therapist can determine specific weaknesses and adjust rehabilitation programs to address these issues. Definition of normal gait Physiological Definition: It is a mechanism that depends upon closely integrated action of the subjects, bones, muscles, and nervous system (including peripheral and central nervous system) The degree of integration determines the different gait patterns. Any defect of any part of them or all of them will lead to pathological gait. Mechanical definition: It is a form of bipedal locomotion as there is an alternating action between lower extremities. One leg is in touch with the ground for restraining, supporting, and propulsion. The other leg is in the swing phase for creating a new step forward. So, gait is the result of a series of rhythmic alternating movements of arms, legs, and trunk which create forward movement of the body. 1 Gait analysis Ass. Prof. Noha Elserty Prerequisites of gait: 1. The ability to support or assume an upright position. (The ability to maintain head, arms, and trunk HAT against gravity) 2. The ability to maintain balance in an upright position during static and dynamic situations. 3. The ability to develop or create new steps forward by controlling foot movement to achieve safe ground clearance and gentle heel contact. N.B: HAT constitutes 75% of total body weight. Phases of Gait cycle Phases of gait Gait cycle: is used to describe the complex activity of walking or our gait pattern. This cycle describes the motions from the initial placement of the supporting heel on the ground to when the same heel contacts the ground for a second time. At 2 Gait analysis Ass. Prof. Noha Elserty normal adult walking speeds, one cycle lasts 1 second and has a length of 1.4 meters. During one gait cycle, each extremity passes through two phases, a single stance phase and a single swing phase. I-Stance Phase: Is defined as the interval in which any part of the foot of one extremity is in contact with the ground (60% of the gait cycle) and it ends when the reference foot lifts off the ground. So, it is called “the supporting phase” or “weight-bearing phase”. stance phase Stance Phase is divided into 5 phases: 1- Initial contact (heel strike): Initial contact is an instantaneous point in time only and occurs the instant the foot of the leading lower limb touches the ground. This phase occurs at about 0%- 2% of 3 Gait analysis Ass. Prof. Noha Elserty GC. The heel is usually the foot section that makes initial contact, but other parts of the foot may contact the ground first in the presence of some pathologic conditions. 2- Loading response (flat foot): The loading response phase occupies about 2%-10% of the GC and constitutes the period of initial double stance. During the loading response, the foot comes in full contact with the floor, and body weight is fully transferred onto the stance limb. During this phase, the body’s impact forces with the ground are absorbed. 3- Mid stance Mid-stance represents the first half of single support, which occurs from 10%- 30% of the GC. It begins when the contra-lateral foot leaves the ground and continues as the body weight travels along the length of the supporting lower limb until it is aligned over the forefoot. In this phase, the body’s COM moves directly over the foot. 4- Terminal stance (heel off): Terminal stance constitutes the second half of single-limb support. It begins with the heel of the reference foot rising and ends when the contra-lateral foot contacts the ground. Terminal stance occurs from the 30%- 50% of GC. 5- Pre-swing (toe off): Pre-swing occurs when only the toe of the reference limb is in contact with the ground. This phase is called weight release or weight transfer. This phase occurs from 50%- 60% of GC. It is the terminal double stance interval. 4 Gait analysis Ass. Prof. Noha Elserty II-Swing phase: Is defined as the interval in which the foot of the reference limb is not in contact with the ground (40% of the gait cycle) and it ends just before the heel strike of the same extremity. It denotes the time when the foot is in the air, so it is called the “non- weight bearing period”. The swing period primarily is divided into three phases: Initial swing, mid-swing, and terminal swing. swing phase 1- Initial swing (acceleration): It is the period from the toe of the reference limb leaves the ground to the mid- swing of the reference limb. This phase is from 60%-73% of GC. 2- Mid-swing: It is the period when the reference limb passes directly under the body. The reference limb reaches the vertical tibial position just before the end of the mid- swing. This phase is from 73%-87% of GC. 5 Gait analysis Ass. Prof. Noha Elserty  3- Terminal swing (deceleration): It is the period from the end of mid-swing to the point just before initial contact. The knee is extending in preparation for a new heel strike. This phase is from 87%- 100% of GC. Intervals of gait cycle: Each gait cycle (stance and swing phase) is subdivided into intervals. I- The stance phase is subdivided into double limb support (initial double stance IDS, and terminal double stance TDS) and single limb support intervals: Intervals of the gait cycle Double limb support (initial double stance and terminal double stance): Initial double stance is when both feet are in contact with the ground. One foot is in initial contact and loading response and the other foot is in pre-swing. 6 Gait analysis Ass. Prof. Noha Elserty Terminal double stance: in the late stance, the ipsilateral foot is in pre-swing, and the contralateral foot is in initial contact and loading response. As velocity increases, double-limb support time decreases. Running constitutes forward movement with no period of double-limb support. In normal walking, the initial double stance takes up about 10% of GC, also the terminal double stance takes up to 10% of GC. Single limb support SLS: is the period when only one foot is in contact with the ground (mid-stance and terminal stance). In walking, this is equal to the swing phase of the other limb. It takes up to 40% of GC. II- The swing phase has one interval as one foot is not in contact with the ground and it takes up to 40% of the gait cycle. Functional Tasks of Gait From a functional perspective, there are three fundamental tasks associated with human gait: weight acceptance, single-limb support, and limb advancement. The stance phase plays a role in all three of these basic tasks, each of its sub-phases contributing to varying degrees. Initial contact and loading response are the two sub- phases primarily responsible for weight acceptance. Single limb stance occurs at midstance and is the time when balance during ambulation is most precarious. The body’s center of mass has shifted laterally and is centered over only one supporting limb at this time. 7 Gait analysis Ass. Prof. Noha Elserty Limb advancement creates forward motion of the body and includes the stance sub- phases of terminal stance and pre-swing; these sub-phases provide propulsive forces to move the limb forward, thereby moving the body forward. The stance sub-phases utilize effective force absorption and efficient energy expenditure to accomplish these tasks. The swing phase is concerned with only one of the three fundamental tasks: limb advancement. Limb advancement during the swing phase requires sufficient clearance of the foot from the floor. The limb performs this activity during the first half of the swing and prepares for initial contact during the latter half of the swing. During the first two sub-phases of the swing phase, initial swing and mid-swing, the limb flexes at the hip, knee, and ankle to functionally shorten the limb so the foot clears the floor. The knee then begins rapid extension in terminal swing to lengthen the limb; this motion increases step length and forms a rigid limb in preparation for stability at initial contact. 8 Gait analysis Ass. Prof. Noha Elserty