Factors influencing proprioceptive accuracy: An analysis of the joint position reproduction test

The Joint Position Reproduction test (JPR) is one of the most widely used methods to assess proprioceptive accuracy. It was revealed that certain characteristics of the test influence the acuity. However, some studies show contradicting results, and interactions between factors were also revealed. In this study, we investigated how the effect of starting position, movement type (active or passive), speed, magnitude, and time spent at the target position influences error magnitude and direction. We implied a full factorial 2 (starting position: 30 or 150°) * 2 (movement type: active or passive) * 3 (movement amplitude:30, 60 or 90°) * 2 speed (12 or 24°/sec) * 2 (time spent at target: 2 or 4 s) within subject design, measuring the left elbow joint, and analyzed the data of 135 university students, using generalized linear mixed models. In the first model, where the outcome variable was absolute error, we found a significant main effect of movement type, speed, and amplitude, and significant interactions of amplitude*speed, amplitude*starting position and amplitude*speed*error direction. Higher movement amplitudes and speeds, and passive motion, lead to higher error scores. The deteriorating effect of amplitude was magnified by speed; the staring position*amplitude interaction shows the possible effect of target position. In the second model, where the outcome variable was error direction, we found a significant starting position main effect, and significant starting position*speed and starting position*amplitude interactions. Participants tended to make errors towards the starting position, higher speed and amplitudes increased this tendency. The results have important consequences regarding the standardisation of the JPR. Namely, to ensure comparability, we recommend standardising for the type (active or passive), amplitude and speed of movement and target position.