1. This document discusses the kinetic analysis of forces acting on the body during gait, including external forces like gravity and ground reaction forces, as well as internal muscular forces. 2. It describes the pathways of the line of gravity and ground reaction force vector during the gait cycle. Gravity acts to produce torque at joints unless its line passes through the joint axis, while muscles must contract to counteract the torques from gravity and ground reaction forces. 3. The document analyzes muscle activity during gait based on the direction of the ground reaction force vector at different joints and phases of the gait cycle. It determines whether muscles contract concentrically or eccentrically to either aid or counteract motion

1. KINETIC ANALYSIS
By:H.a.maaz
OPT

2. Forces acting on the body During gait.
- - External forces: gravitational force,
ground reaction force and inertia.
- - Internal forces: active muscle
force, passive (ligaments, tendons,
capsules, bony components).

3. 1- gravitational force
- point of application : COG
-Line of action: LOG.
-Direction: vertical downward.
- Magnitude: W

4. LOG: imaginary vertical line
passes perpendicularly in the
body through the COG.
Pathway from lateral view:
Vertex
-mastoid process
-anterior to atlantooccipital joint
-behind cervical spine
-anterior to the body of dorsal
vertebrae
-posterior to the body of lumbar
vertebrae
-anterior to the second sacral
vertebrae
-behind or through the hip joint

5. Effect of gravitational force on body segments
- Depends on location of the LOG relative to axis
of motion.
- Through the axis: no torque
- At a distance: gravitational torque produced that
causes motion of the body segment around the
axis of rotation.
- Gravitational torque tends to cause anterior
motion of the proximal segment.
- magnitude of torque depends on the distance
between LOG and the joint axis.
- The gravitational torque is opposed by a
counterbalancing torque by active muscle
tension and passive tension in ligaments and
joint capsules.

6. 2- ground reaction force
- point of application :
COP
-Line of action: GRFV.
-Direction: upward.
-Magnitude: ma

7. COP

8. GRFV

9. GRFV

10. Pathway of GRFV
IC LR MS TS PS
Hip A A P P P
Knee A P A A P
ankle P P A A A

11. Gait

12. Frontal plane

13.  Prime movers
 Stabilisers
 Muscle contraction
mode:
• concentric
• eccentric
• isometric
Internal forces: primarily by the muscles. Assisted
by ligaments, tendons, capsules, bones.
To counterbalance the moment created by the GRFV.

15. Analysis of muscle activity during
Gait
General principles:
- Identify the acting muscle and the type of muscle
contraction.
1- identify the pathway of the GRFV and the moment
resulting from this passage. The muscle in the opposite
direction is acting to counterbalance.
2-determine the normal joint motion during this subphase of
gait.
3- * joint motion occurs in the same direction with the
muscles…………Concentric.
*joint motion occurs in one direction and the acting
muscle works in opposite
direction…………………….Eccentric.

16. Analysis of Gait – sagittal plane analysis.
Ankle joint.
IC LR MS TS PS
Ankle P P A A A
0
dorsiflexion
15
Plant Flex
5-10
Dorsi flex
10
Dorsi flex
20-30
Planter flex
10
Plante
Flex
0 0

17. Analysis of Gait – sagittal plane analysis.
Knee joint
IC LR MS TS PS
Knee A P A A P
0
extension
15-20
Flex
5
flexion
0
extenson.
35-40
flexion
40- 60
Flex
65-30
Flex
0
exten

18. Analysis of Gait – sagittal plane analysis. Hip
joint
IC LR MS TS PS
Hip A A P P P
30
Flex
25
Flex
0 20
Hyper ext.
0
20
Flex
30
Flex
30
Flex

19. Pathway of GRFV: Frontal plane
IC LR MS TS PS
Hip L M M M L
Knee L M M M N
ankle N L L M N