Background and Aim : The tracking tests are a known method to measure and quantify the performance of the neuromuscular system. They are also one of the accurate and flexible methods for measurement of the performance capacity of sensory-motor control or sensory-motor coordination. The purpose of the present study was to examine reliability of the torque error during trajectory tracking tasks in trunk region in torque-time plane in healthy subjects.

Materials and Methods: Twenty healthy subjects (7 female and 13 male) randomly performed target tracking tasks with two patterns (sinusoidal and saw shape). The sinus and saw tracking tasks had two periodic cycles included 10 seconds (3 cycles) and 15 seconds (2 cycles). The amplitude of the signal was set at about 30% to 70% of Maximum Voluntary Exertions (MVE) of each participant. The tracking tasks were performed in 6 directions of uniaxial exertion (flexion, extension, left and right rotation, and left and right lateral bending). Absolute error mean and the performance of the tracking task were determined by calculating Relative Root Mean Square Error (RRMSE) for each participant during each trial. Relative reliability (Intraclass Correlation Coefficient: ICC) of the error mean and RRMSE for all participants was determined. Also absolute reliability (Standard Error of Measurement: SEM) and Minimal Detected Change ( MDC₉₅ ) were computed.

Results: The results have shown that ICC, SEM and MDC₉₅ for error mean ranged from 0.5 to 0.87, 0.002 to 0.006 and 0.007 to 0.016, respectively. Also these variables for RRMSE ranged between 0.5- 0.86, 0.05- 0.024 and 0.065- 0.139, respectively.

Conclusion: The repeatability analysis showed high and very high reliability for torque errors ( Error Mean, RRMSE ) measures during trajectory tracking tasks in torque time plane in asymptomatic subjects. Therefore this performance can be used for quantification of trunk controllability and also mentioned variables as reliable parameters in researches.

Keywords: Reliability, Trajectory tracking tests, Torque error, Isometric trunk exertion