1. a Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology , Aalborg University , Fredrik Bajers Vej 7, Bldg. D-3, DK-9220, Aalborg, Denmark
2. b Department of Physiology , National Institute of Occupational Health , Lers⊘ Parkallé 105, DK-2100, Copenhagen East, Denmark