While you cant really injure yourself with a Compex unit, you can cause some rather severe muscle soreness if you increase intensity on some programs too rapidly. Just as with a weight training program in the gym, you want to start nice and easy and only add additional stress when the body has adapted to the current workload. When first getting started with strength programs we recommend beginning with a low intensity in the 15-20 mA range. Since any soreness you experience from these workouts is very delayed, evaluate how you feel 2 days after the initial workout. If soreness is substantial, reduce intensity by 5 mA until you can complete the workout with minimal to no soreness 2 days later. When you can complete your workout with no soreness, you are ready to increase intensity. Increases of 5 mA every other session are recommended. Increasing intensity in amounts greater than this, or more frequently, is likely to lead to sore muscles.