First of all every quad exercise works every quad muscle, don’t get what I’m saying twisted. But there is a wide belief amongst very well educated sports scientists (I was taught this in school as well) that you can’t isolate the quad muscles because they share a common insertion, the quad tendon. Studies seemed to confirm this through EMG activation. But bodybuilders knew for years that wasn’t true, while skinny legged scientists said they were stupid. We now know that there’s a lot more to mus