The human jaw's structure-function relationships are complex. A recent example of this complexity is the lateral pterygoid muscle which we now consider as a single unit made up of functional regions with activity in each dependent on the biomechanical demands of the task. We have also characterised the effects on the jaw motor system of pain or exercise, as examples of how the jaw motor system adapts. Synchronised jaw tracking and electromyographic acquisition systems were used to study the effects on jaw muscle activity of experimentally induced masseter muscle pain or resistance exercises during goal-directed tasks. With both interventions, subjects were able to perform the same movement with different muscle co-activation strategies. In future, the biomechanical effects on the orofacial structures of motor changes with pain/exercise interventions may be investigated with mathematical jaw modelling. Such models could propose clinical interventions that could alter jaw motor function to reduce adverse joint and muscle loads.