Maintain your cardio routine. While your cardiovascular routine won't increase muscle mass, it will better prepare your heart for your more strenuous weightlifting routine. Incorporate 60 minutes of cardio over the course of a week, in three twenty minute increments. This will maintain your heart, while not impeding your muscle focus. If you are a beginner to muscle building, work on your form prior to increasing your power. You can add weight as time passes, but if you have bad form initially, things are unlikely to improve in the future. .