This study examined the correlation between power error (PE) and velocity error (VE) according to the condition and frequency of self-controlled feedback (SCF) during knee extension. One hundred participants were randomly assigned to 30% SCF, 70% SCF, 30% yoked feedback (YF), 70% YF and control group, respectively. The SCF group was provided with feedback when they requested it, whereas the YF group did not influence the feedback schedule. Participants in the control group were not given any visual feedback during the experiment. The isotonic, isometric, and isokinetic dynamometer (PRIMUS RS, BTE, USA) was used to measure the power and velocity error during knee extension. The collected data was analyzed using a Pearson test and SPSS 21.0. The correlation between PE and VE according to the condition and frequency of feedback on each phase during knee extension was significant. Both PE and VE were significantly higher when the feedback was provided with high frequency, passive, and no feedback. Our study suggests that application of SCF can help to improve the proprioception of the healthy person while reducing errors through low frequency and active feedback.

INTRODUCTION
 SUBJECTS AND METHODS
  Subjects
  Study Design and Sequences
  Retention Phase
 RESULTS
  The power error and velocity error according to thecondition and frequency of feedback on each phaseduring knee extension
  Correlation between power error and velocity erroraccording to the condition and frequency of feedbackon each phase during knee extension
 DISCUSSION
 CONCLUSION
 REFERENCES

• Jung Gyu Yoon(Namseoul University) correspondence