If you're looking to tone your back and arms, there are a few exercises you can do to help. For your back, try doing a lat pulldown. This exercise works your latissimus dorsi, which is the largest muscle in your back. To do a lat pulldown, sit at a lat pulldown machine and grip the bar with your hands shoulder-width apart. Pull the bar down to your chest, and then slowly release it back to the starting position. Do 10-12 repetitions.For your arms, try doing a biceps curl.