The chapter began with analyses and literature reviews of elastic
and isometric devices. It was realised that two factors, compatibility
with rate control due to self-centring and proprioceptive feedback,
play the most important roles in determining the differences between
isometric and elastic devices. The literature suggests that an
elastic device may provide richer proprioceptive feedback than
an isometric device. Two experiments involving 6 DOF manipulation
showed that the difference between an elastic device and an isometric
device was not great with respect to performance, but rather with
respect the ease of learning. Due to its richer proprioceptive
feedback, the elastic device was easier to learn than the corresponding
isometric device. After sufficient practice, subjectsÌ
control behaviour apparently became more open-loop, with motor
program based skills, and therefore the richer proprioception
provided by the elastic device was no longer a critical determinant
of performance.