Figure 2. Similar biomechanical constraints for DEFAULT and primed-UP in vertical and horizontal cases contrast with different biomechanical demands between primed-UP and primed-DOWN.

Traces are the averaged projection of the degrees of freedom of the arm along the dimensions relevant to the task goals and the dimensions incidental to the goals. These averages are taken across 100 trials for a typical representative and for 100 frames. Red continuous lines are task-relevant DoF forward. Blue are task-relevant DoF retractions and black are task-incidental DoF traces. Dashed lines are the standard deviation from the mean traces. During forward segments and retractions in the same loop the recruitment, release and balance of the degrees of freedom of the arm tend to markedly change as a function of task complexity.