Walking is the simple act of falling forward and catching self. One foot is always in contact with the ground. and within a cycle, there are two periods of less support and two periods of double-leg support With running, there is a period of time during which neither foot is in contact with the ground, a period called “double float

Winter’ felt walking gait performs five main function

First, it helps to support of the head, arms, and trunk iny maintaining a semirigid lower limb. Second, it helps to maintain upright posture and balance. Third, it can the foot to allow it to clear obstacles and enables gentle heel or toe landing  through eccentric muscle action. Fourth, it generates mechanical energy by concentric muscle contraction to initiate, maintain, and, if desired. increase forward velocity. Finally, through eccentric action of the muscles, it provides shock absorption and stability and decreases forward velocity of the body.

Gait assessment or analysis Most gait analysis today is performed with force platforms to measure ground reaction forces, electromyography to measure muscle activity, and high speed video motion analysis systems to measure movement. Discussion of these techniques, however, is beyond the scope of this book. The various terms commonly used to describe gait, the normal pattern of gait, the assessment of gait, and common abnormal gats are reviewed.

DEFINITIONS 

Gait Cycle

The gait cycle is the time interval or sequence of motions occurring between two consecutive initial contacts of the same foot

For example, if heel strike is the initial contact, the gait cycle for the right leg is from one heel strike to the next heel strike on the same foot. The gait cycle is a description of what happens in one leg. The same sequence of events is repeated with the other leg, but it is 180° out of phase. There are spatial descriptors of gait, such as stride length, step length and step width; time or temporal descriptors, such as cadence, stride time and step time, and, descriptors that involve time and space, such as walking speed.” Another spatial descriptor that is some times discussed with gait is foot angle . Each of these descriptors can and should be very similar for both limbs. For example, osteoarthritis in one hip can change many of the descriptors and the examiner should watch for these changes.

Simoneau clearly described the terminology that applies to the gait evele events

demonstrates the periods or phases of the gait cycle, the function of cach phase, and what is happening in the opposite limb. The gait cycle consists of two phases for each foot: stance phase, which makes up 60% to 65% of the walking cycle, and swing phase, which makes up 35% to 40% of the walking cycle. In addition, there are two periods of double support and one period of single-leg stance during the cycle.

gait As the velocity of the cycle increases, the cycle length or stride length decreases. For example, in jogging, the gait cycle is 70% of the walking cycle, and in running, the gait cycle is 60% that of walking. * In addition, as the 18 speed of movement increases, the function of the muscles changes somewhat, and their clectromyographic activity may increase or decrease. Generally, gait velocity decreases with age. Montero-Odasso et al. found the gait veloc ity (less than 0.8 m/sec) could be used to determine mobility impairment in the elderly.

Stance Phase

The stance phase of gait occurs when the foot is on the ground and bearing weight . It allows the lower leg to support the weight of the body and, by so doing, acts as a shock absorber while allowing the body to advance over the supporting limb. Normally, this phase makes up 60% of the gait cycle and consists of five subphases, or instants.

Stages (Instants) of Stance Phase

• Initial contact (heel strike)

 • Load response (foot lat) Mid Stance (single leg stance 

• Terminal stance (heel off)

•Preswing (toe off)

The initial contact instant is the weight-loading or weight acceptance period of the stance leg, which accounts for the first 10% of the gait cycle. During this period, one foot is coming off the floor while the other foot is accepting body weight and absorbing the shock of initial contact. Because both feet are in contact with the floor, it is a period of double support or double leg stance.

The load response and midstance instants consist of the single support or single-leg stance, which accounts for the next 40% of the gait cycle. During this period, one leg alone carries the body weight while the other leg goes through its swing phase. The stance leg must be able to hold the weight of the body, and the body must be able to balance on the one leg. In addition, lateral hip stability must be exhibited to maintain balance, and the tibia of the stance leg must advance over the stationary foot.

The terminal stance and preswing instants make up the weight-unloading period, which accounts for the next 10% of the gait cycle. During this period, the stance leg is unloading the body weight to the contralateral limb and preparing the leg for the swing phase. As with the first two instants, both feet are in contact, and so double support occurs for the second time during the gait cycle.

Swing Phase

The swing phase of gait occurs when the foot is not bearing weight and is moving forward. The swing phase allows the toes of the swing leg to clear the floor and allows for leg length adjustments. In addition, it allows the swing leg to advance forward. It makes up approximately 40% of the gait cycle and consists of three subphases.

Subphases (Instants) of Swing Phase

• Initial swing (acceleration)

• Midswing

Terminal swing (deceleration)

Acceleration occurs when the foot is lifted off the floor: During normal gait, rapid knee flexion and ankle dorsiflexion occur to allow the swing limb to accelerate forward. In some pathological conditions, loss or altera tion of knee flexion and ankle dorsiflexion leads to altera tions in gait

The midswing instant occurs when the swing leg is adjacent to the weight-bearing leg, which is in midstance. During the final instant (terminal swing or deceleration), the swinging leg slows down in preparation for initial contact with the floor. With normal gait, active quadriceps and hamstring muscle actions are required The quadriceps muscles control knee extension, and the hamstrings control the amount of hip flexion.

During running or with increased velocity, the stance phase decreases and a float phase or double  unsupported phase occurs while the double support phase disappears. Although the single leg stance phase decreases, the load increases two or three times. The motion occurring at each of the joints (pelvis. hip, knee, ankle) is similar for walking and for running, but the required range of motion (ROM) increases with the speed of the activity. For example, hip flexion in walking is about 40° to 45°, whereas in running it is 60″ to 75

Double-Leg Stance

Double-leg stance is that phase of gait in which parts of both feet are on the ground. In normal gait, it occurs twice during the gait cycle and represents about 25% of the cycle. This percentage increases the more slowly one walks; it becomes shorter as walking speed increases (Figure 14-6) and disappears in running

Single-Leg Stance

The single-leg stance phase of gait occurs when only one leg is on the ground; this occurs twice during the normal gait cycle and takes up approximately 30% of the cycle

NORMAL PARAMETERS OF GAIT-

The parameters that follow and their values are consid cred normal for a population between the ages of 8 and 45 years. It should be pointed out, however, that a rela vely normal gait pattern is seen in persons as young as 3 years of age. There are, however, differences between individuals of the same sex and between men and women 25 For the majority of the population outside of these ages, there are alterations caused by neurological development, balance control, aging, changes in limb length, and maturation. For example, with maturity, walking velocity and step length increase, and cadence decreases 20 It is also important to evaluate gait on the basis of normal gait for someone the same age. This is especially true for children.

Base (Step) Width

The normal base width, which is the distance between the two feet, is 5 to 10 cm (2 to 4 inches; Figure 14-7). If the base is wider, the examiner may suspect some pathol og leg., cerebellar or inner ear problems that results in poor balance, a condition such as diabetes or peripheral neuropathy that may indicate a loss of sensation, or a musculoskeletal problem (e.g., tight hip abductors). In the first two cases, the patient tends to have a wider base To maintain balance. With increased speed, the base width normally decreases to zero, and in some cases, crossover

occurs, in which one foot lands where the other should and vice versa. Such crossover can lead to gait alterations and other problems.

Step Length

Step length, or gait length, is the distance between suc excessive contact points on opposite feet. Normally, this distance is about 72 cm (28 inches) being relatively constant for each individual (i.c., step length is commonly related to preferred walking speed and should be equal for both legs. It varies with age and sex with children taking smaller steps than adults and females taking smaller steps than males. Height also has an

Gait Descriptors or Parameters Which the Examiner Should Watch for When Observing Gait

Stride: — The sequence of events between successive heel strikes of the same foot

Step — The sequence of events between successive heel strikes of the opposite feet

Stride length: — The distance between two successive heel strikes of the same foot (average: 144 cm or 57 inches) The distance between successive heel

Step length: strikes of two different feet (average: 72 cm or 28 inches) The lateral distance between the heel

Step or Base Width: centers of two consecutive foot contacts (average: 8 to 10 cm or 3 to 4 inches)

Cadence (step rate): Number of steps per minute (average: 90 to 120 steps/minute)

Stride time: Time for a full gait cycle

Step time: Time for completion of heel strike of right foot to heel strike of left foot Distance covered in a given amount of time

Walking or gait speed: (average: 1.4 m/second or 3 mph)

*All other values will vary depending on walking speed, 

effect: a taller person takes larger steps. Step length tends to decrease with age, fatigue, pain, and disease. If step length is normal for both legs, the rhythm of walking is smooth. If there is pain in one limb, the patient attempts to take weight off that limb as quickly as possible, altering the rhythm

Stride Length

Stride length is the linear distance in the plane of progres sion between successive points of foot-to-floor contact of the same foot. The stride length is normally about 144 cm (56 inches) and in reality is one gait cycle.” Stride length, like step length, decreases with age, pain, discase, and fatigue.  The age changes are often the result of decreased walking pace or speed. 

Lateral Pelvic Shift (Pelvic List)

Lateral pelvic shift, or pelvic list, is the side-to-side move ment of the pelvis during walking. It is necessary to center the weight of the body over the stance leg for balance (Figure 14-8). The lateral pelvic shift is normally 2.5 to 5 cm (1 to 2 inches). It increases if the feet are farther

apart. The pelvic list causes relative adduction of the weight-bearing limb, facilitating the action of the hip adductors. If the abductor muscles are weak, a Tren delenburg gait results (see Figure 14-21).

Vertical Pelvic Shift

Vertical pelvic shift keeps the center of gravity from moving up and down more than 5 cm (2 inches) during normal gait. By means of a vertical pelvic shift, the high point occurs during midstance and the low point during initial contact; the height of these points may increase during the swing phase if the knee is fused or does not bend because of protective spasm or swelling. The head is never higher during normal gait than it is when the person is standing on both feet. Therefore, if a person can stand in an opening, he or she should be able to move through the opening without hitting the head. On the swing phase, the hip is lower on the swing side, and the patient must flex the knee and dorsiflex the foot to clear the toe. This action shortens the extremity length at midstance and decreases the center of gravity rise.

Pelvic Rotation

Pelvic rotation is necessary to lessen the angle of the femur with the floor, and, in so doing, it lengthens the femur (Figure 14-9). The rotation decreases the 

amplitude of displacement along the path traveled by the center of gravity and thereby decreases the center of gravity dip. There is a total of 8 pelvic rotation with 4 forward on the swing leg and 4 posteriorly on the stance leg. To maintain balance, the thorax rotates in the oppo site direction. When the pelvis rotates clockwise, the thorax rotates counterclockwise, and vice versa. These concurrent rotations provide counter-rotation forces and help regulate the speed of walking.

In the lower limb, rotation is evident at cach joint Figure 14-10). The farther the joint is from the trunk, the greater the amount of rotation. For example, rotation in the tibia is three times greater than rotation in the pelvis,

Center of Gravity

Normally, in the standing position, the center of gravity is 5 cm (2 inches) anterior to the second sacral vertebra; it tends to be slightly higher in men than in women because men tend to have a greater body mass in the shoulder area. The vertical and horizontal displacements of the center of gravity describe a figure-cight, occupying a. 5-cm (2-inch) square within the pelvis during walking. The vertical displacement, which describes a smooth sinu soidal curve during walking, can be observed from the side. The patient’s head descends during weight-loading and weight-unloading periods and rises during single-leg stance.

Normal Cadence

The normal cadence is between 90 and 120 steps per minute which varies, in part, because of the height of the individual. The cadence of women is usually six to nine steps per minute higher than that of men. 3 With age, the cadence decreases, Figure 14-11, A, illustrates the cadence of normal gait from heel strike to toe off showing the changing weight distribution. With pathol ogy or deformity (eg, a cavus foot |Figure 14-11, B]), this weight-bearing pattern may be altered. As the pace of walking increases, the stride width increases, and the tocing-out angle decreases. Gait speed is about 1.4 m/ sec (3 mph)