I had quite a bit of pain from spinning classes in the past and realized several things. I can adjust my road bike down to the smallest increment and the spin bikes that I have ridden do not allow for that. Also, when in the standing position when riding outside my posture is very different than when I am on the spin bike. I took a tape measure in to spin class and attempted to make the measurements as similar as possible as my road bike and that helped some. The best thing though has been to stand when I want to stand and to raise and lower the tension based upon how it feels for me. I took a class as a visitor at another gym with a friend where the instructor attempted to change the tension on the bike I was on and I told him it was my ride, not his. Your body knows what is best for it. Spinning classes have made me stronger on the mountain and road bike and running; but I am in charge of the ride and the best instructors I have had make that very clear. I hope you get an opportunity to try another instructor.