Muscle synergy analysis of human adaptation to a variable-stiffness exoskeleton: Human walk with a knee exoskeleton with pneumatic artificial muscles. - Daisuke Maeda; Kenta Tominaga; Takanori Oku; Hang T. T. Pham; Shin Saeki; Mitsunori Uemura; Hiroaki Hirai; Fumio Miyazaki (Humanoids, 2012)