Investigation of the knee angular velocity proprioceptive behavior as the joint velocity increases

Proprioception plays a crucial role to coordinated movement, which is fundamental for daily activities, exercise, and sports. The proprioceptive perception of joint angular velocity sense has received little attention in terms of research, unlike joint position sense, which has been thoroughly studied (1). The present research was conducted in order to investigate the behavior of the proprioceptive ability to comprehend and reproduce low-to-medium angular velocities in the knee joint in a healthy population. The investigation of the proprioceptive behavior regarding the accuracy of the knee joint angular velocity replication, in different joint angular velocities. 43 young healthy individuals (23 men and 20 women, mean age 20.84 yrs) participated in the present research, and were measured in 5 angular joint velocities, 30o/s, 45o/s, 60o/s, 75o/s and 90o/s, and in a randomized order, by using the “Biodex System 3 pro” isokinetic dynamometer. Five passive demonstration trials were followed by five active replications. The subjects were blindfolded during the whole procedure and they were blinded to the results, as were the examiners. Only the last 3 replication attempts were used to calculate the average velocity achieved, since the first two were considered as familiarization trials. The subjects appear to have reproduced the angular velocity of 30o/s more accurately. There is a statistically significant error in the replication of the rest of the velocities, incrementally increasing as the joint angular velocity increased. The lowest angular velocity of 30o/s showed the less significant replication error, both in absolute value (6.0o/s) and as a percentage (20.0%) of the targeted velocity, while 90o/s had the biggest one (34.9o/s and 38.8%, respectively). Something noteworthy was that the majority of the volunteers tend to undershoot the target velocities. Specifically, the number of subjects that undershoot (in comparison to the sample size) were 28/43, 38/43, 40/43, 41/43 and 43/43 for 30o/s, 45o/s, 60o/s, 75o/s and 90o/s respectively. The present study showed that as the joint angular velocity increases, and the brain cannot be informed on time about the joint motion state and is forced to predict it, the replication error increases. Regarding the unknown in the literature undershooting phenomenon observed in the present study, it seems that as the joint velocity increases and cannot be predicted with accuracy, the brain, from the spectrum of the possible predicted ones, always choses to replicate it with one of those with the lower values. This phenomenon may be an interesting conservative behavior of the brain, as the high joint angular velocities seem to be related with injuries.