Table 4. Summary of variables.

Variables and categories	Descriptions
Reach timing:	Reach-to-grasp reactions have to be completed rapidly to
Reaction time	prevent a fall (i.e. fast contact time). This is achieved via
Movement time	early initiation (reaction time) and/or fast execution
Contact time	(movement time) of the reaching movement.
Reach velocity:	Rapid reach velocity reduces movement time. Shorter
Peak velocity	time-to-peak-velocity suggests faster acceleration of the
Time-to-peak-velocity	reaching hand, whereas longer time-after-peak-velocity
Time-after-peak-velocity	allows more time for correction of the reach trajectory.
Reach trajectory:	Transporting the hand along a shorter path-of-travel (i.e.
Medio-lateral deviation from the “direct-path”	with less deviation from the direct (straight-line path) in
Maximum vertical hand elevation	the horizontal plane and with lower elevation in the
Maximum lateral deviation from the “direct-path”	vertical plane) is more efficient but requires more
	accurate mapping of the final target position.
Reach accuracy:	Reach accuracy is important especially if the graspable
Hand contact position in all three axes	object is small. Both systematic and variable errors
Variability of hand contact position in all three axes	reflect the accuracy with which the target was encoded,
	stored and retrieved from working memory.
Prehension (grasp formation):	Accurate prehension (i.e. achieving a full grasp without
Frequency of full grasp	colliding with the handhold) provides a stable support
Frequency of hand-handhold collision	and anchor to restore postural equilibrium.
Cognitive-task performance:	Impaired cognitive-task performance during the balance
Cognitive-task error rate (dual-task trials relative to	task suggests that both tasks competed for the same
single-task trials)	cognitive resources, and that the combined demands of
	the two tasks exceeded the available capacity.