1. Internal forces during gait
Lecture (5)
Internal forces during gait

2. Objectives of lecture (5)
By the end of this lecture, the student should be able to:
*Describe the pathway of ground reaction force vector during gait in the sagittal plane around the hip, knee and ankle joints and its effect on counterbalancing moment.

3. Pathway of GRFV during gait

4. Sagittal plane pathway of GRFVIC LR
MSt
TSt PS
Hip A P
Knee
Ankle
Frontal plane pathway of GRFV IC LR
MSt
TSt PS
Hip L M
Knee N
Subtalar

5. 1- GRFV pathway.
2- Moment created by GRFV.
3- Counterbalancing muscles.
4- Motion required (arcs).
5- Muscle contraction
1- GRFV posterior to knee.
2- Flexion moment.
3- Quadriceps muscle.
4- Flexion ( degrees).
5- Eccentric contraction.

7. Sagittal plane kineticsLR
MSt
TSt PS IS
MSw
TSw
1- GRFV = A
2- Flex. M
3- Hip Ext.
4- Flex.
5- Ecc.
4- Ext.
5- Conc.
1- GRFV = P
2- Ext. M
3- Hip Flex.
No or little activity
Momentum= mv
As in IC
3- Knee Ext.
Flex.
Ecc.
3- No muscle
Ankle plantar flexors
Momentum of contralateral extremity
GRFV
3- Knee Flex.
Ext.
Flex
2- Plant.
3- Dorsiflex.
4- Dorsiflex
4- Plantar F.
2- Dorsi F
3- Plant. F.
4- Dorsi F.
4- Plant. F.
3- Dors F. 4- Dors F. 5- Conc.
3- Dors F. 4- Dors F. 5- isom.

8. Assignment of Lecture (5)
On biomechanical basis explain the following.
Knee extensors are not active during midstance and terminal stance.
No muscular activity is needed from the hip joint in midswing.
Eccentric activity of plantar flexors are required in midstance and terminal stance.

9. On biomechanical basis explain the following.
Hip flexors and extensors activities during stance and swing phase of gait.
Knee extensors activity during gait cycle.
Ankle dorsiflexors activity during whole gait cycle.

10. References
Neumann D.A. (2013): “Kinesiology of the musculoskeletal system, foundation for physical rehabilitation” 3rd edition Mosby Elsevier USA.
Perry J. (1992): “Gait Analysis, normal and pathological function” Slack Incorporated, USA.
Norkin C.C. and Levangie P.K. (1992): “ Joint structure and function, A comprehensive analysis” 2nd edition FA Davis Company, USA.