How can i avoid back injury when i do lunges and crunches?

Painful Lunges: Leaning forward during the lunge can prevent you from getting the fullest benefit of the exercise and may cause added back pain in the lumbar region. If you don't tuck the hip under correctly, you may end up arching your back, which will only aggravate the anterior pelvic tilt and cause pain. Additionally, the front knee must be kept from moving forward during the lunge.