I'm so glad you posted this! I have been experiencing the exact same thing after my Stott Pilates workouts. I only do this class once a week, (I do easier workouts like walking and rebounding the other days) But pilates is my hardest workout by far and my legs start quivering and basically turn into Jello half way thru the workout. It takes about a day and a half to finally have it go away! My legs after the workout stop shaking, but if I put any resistance to them, they quiver...if that makes sense. I really was getting worried myself, but really think it's just my muscles worked to fatigue. Isn't that how we get stronger? Anyway, just my thoughts.