I have been taking spin classes for 7 years. sometimes i notice my knees ache but its only when i am spinning is this bad? what can i do? iam only 25

Overuse?: Cycling is a great exercise for knees in general. If done too often and for too long if a duration certainly the knees can ache. Try taking a longer break between sessions. Cross training with something else low impact like swimming might help as well. If the pain continues see a doc

Variable: Check out your shoe set up, insoles bike position, gluteus strength, biomechanics of the motion. Pedal from your hips, not knee. Consider lower intensity days...As spin classes tend to all be high intensity testosterone festivals.