[header] How to gain muscle without weights [title] Work out a routine that rotates among strength-training exercises. [step] When you're not using weights, your body becomes the " weight " that you use to build muscle. For instance, a pushup, where you're pushing your body off the floor, uses your body's weight to build muscle. 
However, you can't just stick with 1 exercise. You need to rotate through exercises to build up muscle across your body.