Kinetics and kinematics of gait
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This document discusses the kinetics and kinematics of human gait. It defines kinetics as the study of forces acting on bodies, and kinematics as the study of motion without regard to forces. The document outlines the major forces involved in gait including externally generated forces like gravity and ground reaction forces, and internally generated forces from muscle contraction. It describes the motions and forces at the ankle, knee, and hip joints throughout the gait cycle. Measurement techniques for kinetics like force plates and for kinematics like motion capture are also summarized.
Kinetics and kinematics of gait
- 1. KINETICS AND KINEMATICS OF GAIT Lakshmi nair
- 2. METHODS OF STUDYING NORMAL HUMAN LOCOMOTION KINETICS KINEMATICS DIVISION OF MECHANICS THAT DEALS WITH THE MOTION OF BODIES IT DESCRIBES THE MOTIONS OF THE BODY PARTS RELATIVE TO EACH OTHER DURING THE DIFFERENT PHASES OF GAIT DIVISION OF MECHANICS THAT DEALS WITH FORCES ACTING ON BODIES
- 3. kinetics • Basic principles of kinetics are Sir Issac Newton’s 3 laws of motion Third law For every action, there is an equal and opposite reaction’ Ground reaction force -force transmitted from floor to the foot , passed on up to all body segments -reflection of body weight and acceleration -vertical , anterior – posterior, and mediolateral
- 4. THE FORCES OF MAJOR IMPORTANCE IN ANALYSIS OF HUMAN LOCOMOTION ARE; • 1. EXTERNALLY GENERATED FORCES- • The forces exerted by the pull of gravity • 2. INTERNALLY GENERATED FORCES- • The forces exerted by muscular contraction
- 5. Measurement of external forces • Kinetic analysis makes it possible to measure the magnitude and direction of external forces acting on limb during the different phases of gait • Kinematic analysis makes it possible to determine the locomotion of joint in space • The combination of above 2 methods makes it feasible the calculation of the externally generated moments of force at various joints
- 6. Detailed analysis of human locomotion • Derived from kinetic , kinematic and electromyographic studies of normal subjects walking at normal cadences • For the purpose of sagittal plane analysis, the pattern of walking has been considered in 3 intervals. • 1. heel strike to mid-stance • 2. mid stance to toe off • 3. swing phase
- 8. Ankle joint heel strike Foot flat Mid stance Heel off Toe off swing kinemati cs Neutral 15* Plantar flexion 2-3* Dorsi flexion 15* Dorsi flexion 20* Plantar flexion neutral Kinetics- Ext.force In front of jt DF momt ( 2 ft lb) Back of jt PF momt 20ft lb In front of jt DF (25 ft lb) In front of jt DF (80 ft lb) DF (0 ft lb) Kinetics Int.force Dorsi flxrs EDL,EH,TA Dorsi flxrs eccentric (-slapping) Dorsi flxrs Inactive CM ecc. Calf muscl Eccentric PF burst PF inactive Dorsi flxrs
- 9. Knee joint Heel strike Foot flat Mid stance Heel off Toe off swing Kinemati cs Complete extention flex 20*flexion 15*flexion 178*exten tion 40* flexion 65*flexion (acclern) MS decln Kinetics Int.forces Quadricps :concec centric Quad: eccconc entric Quad; concentric Gastrocne mius, other PF (Soleus,TP FHL,PB,PL) Quad; (control heel rise , begin fwd swing) Quad (accln) hamstrng (declrn) Kinetics Ext forces Behind jt flexion moment 10ft-lb max to flex (30 Force Knee Ft-lb) In front of jt extention momnt 10 ft lb Behind jt Fleion moment 53ft-lb
- 10. Hip joint Heel strike Foot flat Mid stance Heel off Toe off swing Kinematic s 25* flexion 20* flexion Neutral 180* 10-15* ext 20*extn (PUSHOFF) 10*extn Neutral 25*flexn Kinetics Int.forces Glut.max, hamstring, erectorspin ae (eccen) Illiopsoas eccen.(PO) Inactive Add.longs , add.magn Glu. med ,min Kinetics Ext forces In front Rotate pelvis forward In front Behind rotate back 30ft lb Extn momnt 140ft lb (PUSHOFF DOUBLE SUPPORT)
- 11. MEASUREMENT OF INTERNAL FORCES Not practical to quantitatively measure the internally generated moments of force exerted by individual muscles during each instant of gait. Electromyographic studies tell us when a specific muscle is active during the gait and when maximum electrical activity occurs and the magnitude of these forces.
- 12. 0-15 % heel strike phase 15-30 % mid stance 30-45% push off 45-60% acceleration of the swing leg
- 13. MUSCLE ACTIVITY DURING THE GAIT CYCLE • 1. PRETIBIAL GROUP • During the heel strike phase, lengthening contraction(eccentric ) of the foot dorsiflexors lets the foot down from heel strike to foot flat position in a slow and controlled manner. Rest of stance phase, the invertors and evertors act to keep the foot stable in ML direction. • Important for the stability of walking on rough ground or on a hillside
- 14. • CALF GROUP- GASTRONEMIUS AND SOLEUS • - max activity during the push off phase to propel the COG up and forward • QUADRICEPS GROUP- Max activity after heel strike , acting as shock absorbers to control knee flexion to 15 deg.
- 15. • HAMSTRINGS GROUP- double peak of activity just before and after heel strike.first peak occurs during swing , and it keep the knee from buckling.second peak at the termination of stance phase working toward hip and knee extension for push off.
- 16. • ABDUCTOR GROUP- GLUTEUS MEDIUS AND MAXIMUS • - Active during heel strike and early stance phase to stabilise the pelvic tilt to 5 deg. • ADDUCTOR GROUP- 1. after heel strike, they assist abductors to stabilise the pelvis 2. end of stance phase, they work together with other hip flexors to accelerate the limb forward in preparation for swing
- 17. • GLUTEUS MAXIMUS- more active during heel strike phase, when it acts as a shock absorber. Their extension function keep both hip and knee from buckling. • ERECTOR SPINAE- becomes active during heel strike and its activity is necessary to keep the trunk from folding forward from the force of inertia and gravity. Also stabilises the trunk mediolaterally.
- 18. Kinetic analysis Recent advances…. • Discrete components of force acting over specific areas of foot or the distribution of pressure also measured. Methods Ultra thin Mylar pressure – resistive sensors and specialized software Floor embedded pressure sensor mats Uses Assessment of the deformed , insensate or painful foot Evaluation and fitting of customized, foot or ankle – foot orthosis
- 19. Kinematic analysis recent advances…. • Techniques • 1. ink and paper • 2. foot switches • 3.instrumented walkways • 4.Electronic Gait Mat II- 3.8 m , 10,000 electronic switches scanned at 100hz ‘electronic foot print’- provides data about walking speed, cadence, stance, swing periods and lengths, width of base of support, both sides can be compared, comparisons with normal age, gender, speed done
- 20. • Motion analysis- • - measured in 3 dimensions Techniques 1. photographic and cinematographic analysis 2. accelerometers and electrogoniometers 3. optoelectronic apparatus
- 23. 3D marker based gait analysis
- 24. • THANK YOU
Editor's Notes
- #6: Measurement of external forces. Using force plates the magnitude and direction of forces acting on limb is determined by force plate studies. The position of joint in space determined by photographic technique.
- #13: For detailed study of human locomotion, the gait cycle is divided into 3 phases heel strike to midstance ms to toe off and swing phase