Biomechanics (original) (raw)

The study of mechanics involves the appreciation of the mass of a body and its inertia and of the interaction of mass and gravity to produce the object's weight. Newton's laws describe forces and their interaction with masses to alter their motion. Examples of unbalanced forces (those that will change an object's motion) are gravity, friction and the contraction of skeletal muscle. The bones of the skeleton may be thought of as levers that turn around the synovial joints (the fulcra) when skeletal muscles provide the effort force. The load force is the weight of the limb being moved along with whatever is being held by or being made to move by the limb. Many configurations of bone, muscle and joint that occur in the body can be described as third class lever systems, and hence as "inefficient". That is, the effort force produced by contracting muscles is greater than the load force to be shifted. Correct and safe patient handling procedures (manual handling), involves minimising the amount of lifting by asking the patient to move themselves-and instructing them how to. If the carer is required to shift a patient, manual handling also involves minimising the use of weak muscles and bones, such as those of the back. Instead, the strong muscles of the legs are used; the length of the load arms are minimised (by getting your centre of gravity close to the load), and friction is minimised by using a slide sheet or board. Furthermore correct technique requires that stability is maintained (by keeping your centre of gravity over your base of support), and that the help of gravity, and other health care workers, is enlisted.