Could be. My first thought is the glutes which are part of the "core".

I'd be curious to see what your results are after trying it a while. There's 2 things I know of:

1. On the one hand, you can get decently increased power and endurance if you can get everything in your body to align better. So like rather than just using your quads pedalling, if everything lines up you can get quads, glutes, and core all working together.

2. On the other hand, when people run into this (including myself), we often find that the new way to pedal has a lot less endurance than the old way. Probably you were using more quads before, your quads got warn out, you shifted to using glutes which were still fairly fresh. But it doesn't last - your glutes also get worn out and a lot faster than your quads.

Could be either, I'd be curious to see how it goes.