Energetics & Force Translations

Simply put, in order for motion to exist it requires energy. This energy is produced mainly by the skeletal muscles in the body, transferred via the tendons to the skeleton to produce the desired movement. However there are other forces acting from within and outside the body, having an overall effect on the movement.

The four common properties of force are:  line of action  point of application

Contact Forces

These are reaction forces involving contact and are divided into:

 Contact forces

 Non-contact forces (ie gravity and weight)

Before we proceed we need to clarify that weight and mass is not the same entity. Weight is dependant on the amount of gravity acting on and object or body. Mass is the constituent matter in an object or body. Therefore if you went into a vacuum negative gravity chamber, your body mass remains constant, while your body weight decreases due to lower gravity acting on it. We transfer forces in everyday life and in sports. The simplest actions such as turning around a street corner when walking, will require you to step a little harder to ensure sufficient pivot to change from a liner motion line (straight line), to a curved motion line (displacement: taking the turn). In sport, a rugby or tennis player will have to exert similar motion patterns with greater exertion of force in order to turn around or side-step.

Point to consider for therapists & coaches: If you cannot appreciate motion mechanics of daily living such as walking, a housewife in the kitchen, or an infant learning how to move, it will be of greater difficulty to understand motion in sports, as most movement patterns have great similarities, with the only variable being: acceleration and force.

Contact Forces

The majority of contact forces result from contact between objects and body mass, and may manifest as any one of the following types:

 Ground reaction forces

 Joint reaction forces

 Friction forces

 Fluid resistance forces

 Inertial forces

 Elastic forces