Rowing is very hard on the back. More lower back injuries are reported from rowing than other body part. Upper arm kinks are nothing compared to a lower back strain. In order to protect your back, you need to learn and follow proper rowing form. Techniques such as keeping your head straight and pulling the oars evenly are vital to know before rowing for any distance. Cross training should include both aerobic and strength exercises. Strengthen your core to best protect your back. Nothing beats crunches for strengthening the core. Strong ab muscles will be your best defense against back strain. Add twisting to your crunches and sit-ups to strengthen the side oblique muscles groups.