My 21 year old son has a 5 month old Rottie. He lives in an apartment. How does he make sure his Rottie gets enough exercise?
In spite of their size, adult Rottweilers don’t need a huge amount of exercise and can live happily in an apartment or small house as long as they get walked daily and have at least one play or training session per day as well.
It’s not advisable to over-exercise large-breed pups before their bone structure etc. is fully developed. However at 21 months your sons’ pup is getting close to being mature (although he may not fully finish growing until he’s 2 1/2 years or older, so as long as it’s not jumping from any real height, or pounding the concrete for hours, he should be okay with most things.
In addition to at least one daily brisk walk, enrolling the pup in a formal obedience class would be beneficial as training the mind is as important as training the body. The effort and low-level stress the pup will feel from the class will tire him out, plus your son will then need to conduct short daily training sessions with him which will add to his activity level.
Rottweilers often have a great ball drive (ie love to play with balls of all sorts), and just taking his pup to the park and throwing the ball a couple of dozen times will provide an outlet for the pups energy. Dogs also use chewing as a way of expending excess energy and working out any tension, so providing tons of safe and sturdy chew toys (see my Tough Dog Toys when the pup is home is beneficial.
Hope this helps, best of luck with that pup.