The purpose of this study was to investigate changes in wrist extensor activity, pain, and grip strength before and after wearing a forearm strap in their 20s who complained of chronic lateral epicondylitis for more than 6 weeks. As a result of the study, there was an increase in wrist extensor activity on both the injured and non-injured sides after wearing the forearm strap, but this was not statistically significant. There was a statistically decrease in pain after wearing the forearm strap on the injured side, and a statistically significant increase in grip strength on both. After applying the forearm strap with pad, there was an increase in muscle activity of ECRB (extensor carpi radialis brevis) on both the injured and non-injured sides. This is thought to be due to the strap pad acting as a com- pressive force, reducing pain, and increasing muscle recruitment ability due to stability in wrist extension. However, considering that the number of study subjects is insufficient to generalize the results, additional supplementary research is deemed necessary.