The use of a novel assessment protocol for the knee joint velocity proprioceptive sense to investigate motor learning abilities

Abstract

Proprioception is a significant factor in balance, coordination, joint stability and movement acuity (1). Among proprioception’s components, joint position sense (JPS) and movement detection have been mostly assessed whereas little is known about the joint velocity proprioceptive sense (2). Finding the joint angular velocity(-ies) that is more comprehensible by the human’s brain, and therefore more accurately reproduced, could be used, among others, in motor learning rehabilitation protocols. To investigate the knee angular velocities envelope inside which the joint can be moved with the most accuracy, depending on the task. 48 subjects (23 men and 25 women) without knee pathology participated in the study (age 21.4 ±3.85). Velocity replication (VR) was assessed in a spectrum of 5 different and randomly chosen low velocities (2°/s, 5°/s, 10°/s, 20°/s and 30°/s) by using concentric quadriceps contraction in an Isokinetic Dynamometer (Biodex System3 Pro). During the procedure the subjects were blindfolded, and the examiners were blind regarding the results.The passive demonstrations of each joint angular velocity were followed by active velocity replications. The number of passive demonstrations and active replications were adapted for each velocity in such a way, that each subject would stay almost the same amount of time, and therefore having the same effect or effort, in all of them. The knee angular velocities of 2°/s and 5°/s had the bigger mean percentage replication errors (68.2% and 29.0%) but the smallest mean errors in absolute value (1.4°/s for both the velocities). In the velocities of 10°/s, 20°/s and 30°/s the mean percentage replication errors were 26.3%, 26.1% and 29.0% respectively, while the mean errors in absolute value were 2.6°/s, 5.5°/s and 8.6°/s respectively. According to the present research, the knee joint can achieve a maximal precision of 1.4°/s angular velocity error, appear in joint velocities below 5°/s. Rehabilitation protocols require precision should focus is this kinematic envelope as, above this threshold, the angular velocity error increases gradually, as the joint velocity increases. For gross motor activities, where percentage joint angular velocity errors are more meaningful than the absolute error values, the kinematic envelope between 10°/s - 20°/s seem to be the ideal for motor learning tasks. According to our knowledge, this is the first attempt in the literature to investigate the knee angular velocity proprioception, and further investigation is needed on the velocity proprioceptive behavior of other joints, as well as any deviations in pathologies or trauma.