Drawing a nude male in a natural pose is a challenge in spite of the obvious familiarity of the form. Compared to other natural objects, our brains easily recognize human proportions, and so failures in depicting those proportions can be jarring. While it is possible to slightly modify proportions with an excellent sense of aesthetics, it is good to start your artistic career by learning anatomical accuracy. Use a male life drawing as your example. It is easier to obtain than hiring a real model, and it is easily downloaded from a richly supplied sponsor site.
It is better to use photos or the work of a skilled artist when learning to draw the human form. This is just because correct proportions are so essentials, and undoing bad habits is more difficult than learning good habits. If you do not want to be dependent on a ruler on an artist, then learn correct proportions with an excellent sample.