Generally, a spinning class lasts 45 minutes. It must be abnormal for you to ride for a short time. You may not have mastered the correct posture of riding a spinning bike, and its spinning bike has professional skills (generally, the students who just started riding are riding in the wrong posture, so you should ask the coach to teach you more, or search the standard posture riding method of spinning bike on the Internet). In addition, you should reduce resistance, do what you can, and don't ask the coach to increase. According to your own step by step, riding a spinning bike in the right posture is very physical exercise (mainly to exercise the lower body-legs and hips), but the wrong posture will do harm to your body ~ I hope this answer will be useful to you again.