Bend over, palms can't touch the ground, mainly because the ligaments of leg and back muscles are not relaxed. It is suggested to start doing sit-ups, starting from 10 every night, increasing to 15 after 5 days, and then increasing to 30 after 7 days. You can also bend down and put your face on your knees. Don't be too fierce (try to touch your leg with the tip of your nose first) to avoid pulling without preheating.