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.

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
:concec
centric
Quad:
eccconc
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

22. Visual gait analysis

23. 3D marker based gait analysis

24. • THANK YOU