When I looked for ways to maintain muscularity and strength, I went to my PE department at school and asked the instructor/trainer for a routine. He put me through a cycle of exercises and times that I could do without completely fatiguing me. As time went on I added exhaustion factors (length and intensity) under his guidance. He knew I was a vegetarian (he wasn't) but didn't try to hook me on protein powders, steroids, etc., which were popular at the time.