KINETICS: FORCES AND MOMENTS OF FORCE - Biomechanics and Motor Control of Human Movement - page 107

KINETICS: FORCES AND
MOMENTS OF FORCE

5.0 BIOMECHANICAL MODELS

Chapter 3 dealt at length with the movement itself, without regard to the
forces that cause the movement. The study of these forces and the resul-
tant energetics is called kinetics . Knowledge of the patterns of the forces is
necessary for an understanding of the cause of any movement.
Transducers have been developed that can be implanted surgically to mea-
sure the force exerted by a muscle at the tendon. However, such techniques
have applications only in animal experiments and, even then, only to a lim-
ited extent. It, therefore, remains that we attempt to calculate these forces
indirectly, using readily available kinematic and anthropometric data. The
process by which the reaction forces and muscle moments are calculated is
called link-segment modeling . Such a process is depicted in Figure 5.1. If
we have a full kinematic description, accurate anthropometric measures, and
the external forces, we can calculate the joint reaction forces and muscle
moments. This prediction is called an inverse solution and is a very powerful
tool in gaining insight into the net summation of all muscle activity at each
joint. Such information is very useful to the coach, surgeon, therapist, and
kinesiologist in their diagnostic assessments. The effect of training, therapy,
or surgery is extremely evident at this level of assessment, although it is often
obscured in the original kinematics.