KINETICS_ AND _KINEMATICS _OF_GAIT PT.pptx

this presentation includes the kinetics and kinematics of gait for 2nd year physiotherapy students

1. GAIT -Dr. Raj Mhatre

2. GOALS To understand definition of gait Functions of gait Phases of gait cycle Kinetics and kinematics of gait Characteristics of normal gait Types of gait Measurable parameters of gait

3. INTRODUCTION Defination : human gait is defined as bipedal, biphasic, forward propulsion of center of gravity of the human body, in which there are alternate sinuous movements of different segment of the body with least expenditure of energy.

4. MAJOR TASKS OF GAIT 1. Maintenance of support of the head, arms, and trunk, that is, preventing collapse of the lower limb 2. Maintenance of upright posture and balance of the body 3. Control of the foot trajectory to achieve safe ground clearance and a gentle heel or toe landing 4. Generation of mechanical energy to maintain the present forward velocity or to increase the forward velocity 5. Absorption of mechanical energy for shock absorption and stability or to decrease the forward velocity of the body

5. Gait cycle: it is defined as the time interval or cyclic sequence of movement patterns occurring from the moment of one foot strike the ground to the heel of the same foot striking the ground again. It has 2 phases: Stance phase (60%) Swing phase ( 40%)

6. STANCE PHASE SWING PHASE INITIAL CONTACT EARLY SWING FOOT FLAT MIDSWING MIDSTANCE LATE SWING HEEL OFF TOE OFF

7. STANCE PHASE Initial contact: refers to the instant the foot of the leading extremity strikes the ground. In normal gait, the heel is the point of contact, and the event referred to as heel contact or heel strike. Foot flat: in normal gait occurs after initial contact at approximately 7% of the gait cycle. It is the first instant during stance when the foot is flat on the ground. Midstance: is the point at which the body weight is directly over the supporting lower extremity, usually about 30% of the gait cycle.

8. Heel-off: is the point at which the heel of the reference extremity leaves the ground, usually about 40% of the gait cycle. Toe-off: is the instant at which the toe of the foot leaves the ground, usually about 60% of the gait cycle

9. SWINGS PHASE Early swing phase: begins once the toe leaves the ground and continues until midswing , or the point at which the swinging extremity is directly under the body. This phase is also referred to as initial swing, or the acceleration phase. Midswing : occurs approximately when the extremity passes directly beneath the body, or from the end of acceleration to the beginning of deceleration. Late swing: occurs after midswing when the limb is decelerating in preparation for heel strike. It is also known as terminal swing, or the deceleration phase.

10. KINEMATICS OF GAIT Kinematics is the term used to describe movements without considering the internal or external forces that caused the movements. These measures include position, velocities, and accelerations of body markers or body segments. Time (temporal) and distance (spatial) are two basic parameters of motion, and measurements of these variables provide a basic description of gait. Temporal variables include stance time, single-limb and double-support time, swing time, stride and step time, cadence, and speed. The distance variables include stride length, step length and width, and degree of toe-out.

11. TEMPORAL PARAMETRS 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 when only one extremity is on the supporting surface in a gait cycle. Double-support time is the amount of time spent with both feet on the ground during one gait cycle. The percentage of time spent in double support decreases as the speed of walking increases. Step duration refers to the amount of time spent during a single step. Measurement usually is expressed as seconds per step Stride duration refers to the amount of time it takes to accomplish one stride. Stride duration and gait cycle duration are synonymous. One stride, for a normal adult, lasts approximately 1 second. Cadence is the number of steps taken by a person per unit of time.

12. SPATIAL PARAMETERS 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. Stride length is the linear distance between two successive events that are accomplished by the same lower extremity during gait. 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. Walking velocity is the rate of linear forward motion of the body, which can be measured in meters or centimeters per second, meters per minute. If direction is not mentioned then the term WALKING SPEED should use. Walking velocity (meters/second) = distance walked (meters)/time (seconds

13. Step width, or width of the walking base, 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 center of the heel and the second toe. The angle for men normally is about 7° from the line of progression of each foot at free speed walking.

14. SAGGITAL PLANE KINEMATICS HIP: hip achieves maximum flexion (~+20°) around initial contact at 0% of the gait cycle and reaches its most extended position (~–20°) at about 50% of the gait cycle, between heel-off and toe-off. After reaching maximum extension, the hip begins flexing again, reaching maximum flexion late in swing, at 80–85% of the gait cycle KNEE: In stance phase, knee is straight (0°) at initial contact and nearly straight again just before heel-off at 40% of the gait cycle. The knee flexes 10 to 20° immediately after contact, reaching maximum flexion at about 15% of the gait cycle when the subject achieves foot flat. At foot flat the knee begins to extend and reaches maximum extension at about 40% of the gait cycle as the heel rises from the ground. During the swing phase, the knee reaches its maximum flexion of ~+60° at ~70% of the gait cycle.

15. ANKLE: Ground contact occurs with the ankle close to neutral in either slight plantarflexion or slight dorsiflexion. Following initial contact, the ankle plantarflexes an additional 5 or 10°, reaching a maximum at about 5% of the gait cycle. As the body glides over the stance foot, the ankle dorsiflexes, reaching a maximum just after the knee reaches full extension.. The ankle reaches maximum reaches maximum plantarflexion (–25°) at toe-off (60%). In early swing, the ankle dorsiflexes slightly but may remain in slight plantarflexion throughout swing (10 °) (ref: Carolina oatis ,Kinesiology The Mechanics and Pathomechanics ) of Human Movement PELVIS: Pelvic motions in the sagittal plane are small. pelvis anteriorly tilts whenever either hip is hyperextending that occurs in late stance phase

16. FRONTAL PLANE Frontal plane excursions are less well studied and more varied than sagittal plane movements. HIP and PELVIS : Hip position in the frontal plane is affected by the motion of the pelvis over the femur and by the orientation of the femur as the subject translates toward the opposite foot to keep the center of mass over the base of support. The hip lies close to neutral abduction at initial contact and then adducts during weight acceptance( stance) as the pelvis drops on the contralateral side. Individual shifts laterally to keep the center of mass close to the stance foot, and the pelvis drops on the unsupported side. Adduction continues until late stance, when loading begins on the opposite limb. At that instance, the pelvis drops on the side in late stance, and the hip moves into abduction KNEE: The knee remains more or less neutral, except for a brief abduction peaking at about 7° in midswing , and then returns to neutral. ANKLE: ankle complex everts from about 5° of inversion to 5° of eversion in early stance and inverts about 15° during push-off.

17. TRANSVERSE PLANE PELVIS AND HIP: Pelvic rotation in the transverse plane accompanies hip flexion, so that the pelvis rotates forward on the side of the flexing hip, reaching maximum forward rotation at approximately ground contact. Forward rotation of the pelvis contributes to lateral rotation of the hip . At the same time, the opposite hip is in maximum extension, and the relative backward position of the pelvis on that side allows the hip to appear hyperextended. KNEE: The knee, too, exhibits transverse plane motion with medial rotation following ground contact and gradual lateral rotation from midstance through most of swing . ANKLE: As the foot pronates, the tibia medially rotates and allows the knee to Flex. Later in stance, the foot supinates as the tibia rotates laterally , and the knee extends while the body rolls forward onto the opposite limb.

18. The pelvic position in the transverse plane and the femoral rotation in the transverse plane both contribute to the transverse plane hip joint position during the gait cycle. At ground contact the femur is medially rotating, but the forward alignment of the pelvis contributes to lateral rotation of the hip. At heel off the opposite is true.

19. TRUNK The trunk exhibits slight flexion and extension during the gait cycle, is more erect or extended during single limb support, and is more flexed during double limb support. Frontal plane motion of the trunk is consistent with the need to keep the center of mass over the stance foot. So the trunk leans slightly to the stance limb at each step. Frontal plane motion, trunk leans slightly to the stance limb at each step. In the transverse plane, the rotation of the trunk is opposite the rotation of the pelvis, with the trunk rotating forward on the side in which the shoulder is flexing

20. KINETICS Kinetics is concerned with the forces acting on the body that are the cause of the movement. A kinetic analysis is performed to understand the forces acting on the foot by the supporting surface, the forces acting on the joints, the forces produced by muscles, the moments produced by those muscles crossing the joints, the mechanical power generated or absorbed by those muscles, and energy patterns of the body during walking.

21. GROUND REACTION FORCES: are the forces being applied to the foot by the ground when a person takes a step. These forces are equal in size (magnitude) but opposite in direction to the forces applied to the ground by the foot. GRFs are expressed using vertical, anteroposterior, and mediolateral axesThe ground reaction force is measured directly by force plates imbedded in the walking surface. GROUND REACTION FORCE VECTOR: If we combine the force components in two or three planes, the vector sum is a single expression of the ground reaction force and is termed the ground reaction force vector CENTER OF PRESSURE OF THE FOOT: The COP of the foot on the supporting surface is the point where the resultant of all the floor-foot forces act.

22. MOMENT OF FORCE: also known as moment or torque. It is defined as the product of the force (usually muscle) and the perpendicular distance from its action line to the joint center. It can be thought of as the tendency to turn. τ = ( F)(d) or τ = ( F)(MA) INTERNAL MOMENT: this are the moments generated by the muscles, joint capsules, and ligaments to counteract the external forces acting on the body. EXTERNAL MOMENTS: External forces such as the ground reaction forces produce external moments about the joints.

23. ENERGY: is the capacity to do work. both work and energy are expressed in the same units, joules (J). METABOLIC EQUIVALRNTS ( MET’S): Metabolic equivalents is a term use to express energy cost of the activity as multiples of the resting metabolic rate. POWER: Mechanical power is the product of force and linear velocity or, in rotational motions such as the joint movements in locomotion, the product of joint moment and angular velocity: POWER GENERATION is accomplished when muscles shorten (concentric contraction

24. DETERMINANTS OF GAIT The determinants of gait are biomechanical factors that help minimize displacement of the center of gravity during walking, making human locomotion smoother and more energy-efficient. The classic six determinants described by Saunders, Inman, and Eberhart are: Pelvic Rotation: The pelvis rotates in the transverse plane (about 8° total), allowing for a longer step and reducing vertical displacement of the center of gravity. Pelvic Tilt: During the stance phase, the pelvis tilts downward on the side opposite the weightbearing limb (around 5°), further minimizing the rise of the center of gravity Knee Flexion in Stance Phase: After heel strike, the knee flexes (about 15–20°), absorbing shock and reducing abrupt changes in center of gravity.

25. Foot and Ankle Mechanism: At heel strike and push-off, the foot and ankle move (dorsiflexion and plantarflexion), lengthening the limb and smoothing the pathway of the center of gravity Knee Mechanism: Knee motion during stance and swing phases works with the foot and ankle to control center of gravity displacement. Lateral Displacement of the Body: The center of gravity shifts laterally over the stance foot for balance, minimizing unnecessary side-to-side movement. Minor determinants include neck movement and arm swinging, which also contribute to gait efficiency. In sum, these determinants help ensure that gait is not only efficient and smooth but also stable and graceful

26. SAGGITAL PLANE MOMENT AND CENTRE OF PRESSURE

27. NORMAL GAIT TREADMILL GAIT