Chapter 11 Flashcards
What is Biomechanics?
Biomechanics is the understanding of our bodies’ behaviour and function as it is acted upon by forces.
External forces
forces that originate outside the body. We cannot see these forces, but we can feel them, and measure them. Gravity and wind resistance are examples of an external force that could either work to our advantage or disadvantage. An example of gravity is skydiving as gravity will bring you back down to land.
Internal forces
arise within the human body. Our muscles are linked to our bones by tendons at origin and insertion points. When a muscle contracts, a force is generated that results in a movement of the bone to which it is attached. An example of this would be, a bicep curl. Concentric contraction of the biceps muscle; eccentric contraction of the triceps muscle; weight moves upward
Newton’s first law - law of inertia
a body in motion tends to stay in motion and a body at rest tends to stay at rest unless acted upon by an external force. Example: when a gymnast holds a stationary pose on a balance beam.
Newton’s second law - the law of acceleration
a force applied to an object causes an acceleration of that object of a magnitude proportional to the force and in the direction of the force, but inversely proportional to the object’s mass. In other words F=ma. Example: every time an object such as a basketball is thrown into the air, the resulting motion or change in shape will occur in the direction in which the force is applied. The rate or velocity at which the ball moves will change when a force is applied to it.
Newton’s third law - action and reaction
for every action, there is an equal and opposite reaction. Example: when a basketball player jumps to make a slam dunk, the action of pushing against the court floor leads to a reaction force. Ultimately the athlete’s body leaves the ground.
First class levers
the fulcrum is located between the point of application of the muscular force and the resistance being moved. An example is the neck as it shifts from a position of flexion to a position of extension (looking straight to looking up).
Second class levers
which the resistance is positioned between the point of application of the muscular force and the fulcrum. An example of this would be, the ankle joint in combination with contraction of the gastrocnemius muscle.
Third class levers
which the point of application of the muscular force is found between the fulcrum and the resistance. An example of this would be, a bicep curl. The bicep muscle inserts on the radius in combination with the elbow joint.
Linear motion
when a body moves the same distance in the same direction in the same amount of time. Straight line motion. An example, running straight ahead.
Angular motion
features a rotation or turning about an axis. Does not act through the centre of an object or the body. An example, a figure skater spinning.
Centric force:
a force applied directly through the centre of an object. Results in linear motion only.
Eccentric force:
a force directed through a point other than the centre of an object, results in rotational motion. (Sometimes linear but rarely)
