It's a Troubletones reunion and a salute to perseverance on next week's 'Glee' when Brittany, Mercedes and Santana team up to perform Kelly Clarkson's 'Stronger (What Doesn't Kill You).'The song appears in the 'On My Way' episode, which finds the vocal groups battling for supremacy at the Show Choir Midwest Regional Championship. Preview images for the episode show the ladies belting out the song with their fists raised in a sign of unity and strength.

With no changes to the basic structure of the song, the differences between the 'Glee' and Clarkson versions are mainly due to the additional harmonies and vocal freelancing over the final chorus. It's hard not to get caught up in the excitement when they sing the hook: "What doesn't kill you makes you stronger / Stand a little taller / Doesn't mean I'm lonely when I'm alone / What doesn't kill you makes a fighter / Footsteps even lighter / Doesn't mean I'm over cause you're gone / What doesn't kill you makes you stronger, stronger / Just me, myself and I."

The girls have a difficult job trying to match the intensity and spirit of Clarkson's chart-topping performance, but they capably re-create the song. See their performance in the 'On My Way' episode on Feb. 19.

Listen to the 'Glee' Cast's 'Stronger (What Doesn't Kill You)'