Biomechanic

1. Introduction
to
Biomechanics

2. The Musculo-skeletal System
Muscular System
• Almost ½ the body’s weight is muscle
• There are more than 640 muscles in the
body
• Muscles can shorten and pull but not push
• Most muscles are arranged in opposing
teams e.g. agonistic/antagonistic - as each
team pulls, the other team relaxes and gets
stretched

4. The Musculo-skeletal System
Skeletal System
The skeleton has 3 major roles
3. It protects vitals organs
4. It provides body shape
5. It allows us to move as our muscles are
attached to our bones – when our
muscles move – our bones move to.

6. Skeletal System
Skeletal System Factoids
• You are born with 350 bones but
only have 206 bones as an adult –
some bones fuse together to form
one bone

8. Bone Structure
• A typical bone has a strong outer layer
of compact bone
• Inside is a layer of flexible spongy bone
which looks like honeycomb
• The middle of some bones consist of a
jelly-like substance called bone marrow
which is where new red blood cells are
produced

9. Bone Structure

10. Naming Skeletal Muscles:
Location – e.g. intercostals
Shape of Muscles – e.g. Deltoid –
triangle
Size – e.g. Longus, maximus
Direction of muscle fibres – e.g.
transverse, oblique
Number of muscle parts e.g. quadriceps

11. Biomechanics
• The study of mechanics in the human body
• Divided into 2 areas
3. Kinetics – the forces producing motion e.g.
muscles, gravity
4. Kinematics – the description of motion e.g.
type, location, direction, planes of
movement

13. Biomechanics
• The human skeleton is a system of
levers
• Muscle force moves the skeleton
3 types of levers in the body
4. Class 1
5. Class 2
6. Class 3

14. Class 1 Levers

15. Class 2 Levers

16. Class 3 Levers

17. Note the contact point

18. The Lever Arm

19. Moments or Torque

20. Mechanical Disadvantage

21. Effort and Angles

22. Forces in Your Body
• When you walk, there is 2 to 3 times your
body weight transmitted through each foot.
• When you run, this is 7 to 8 times
• The foot has 26 bones – everything must be
functioning correctly to avoid injury
• E.g. flat feet
Click here to view a graphical representation of flat feet (online)

23. Forces in Your Body
• When you sit with bad posture, there is a
200% increase pressure in your spine.
• Reaching for your toes is a 300% increase
• Human movement is very complex. There
may be dozens of joints and muscles working
to achieve a desired movement.

24. Biomechanics in Physiotherapy
• It is essential to have a thorough
knowledge of what is “normal” for the
human body.
• i.e. knowing the resultant action if a
muscle contracts
• i.e. knowing the possible result of a
muscle not functioning correctly