My Grandpa would do things like stack 80-90 pound hay bales and 100 pound sacks of fruit all day long. He once shoveled over 20 tons of fruit into transport bins in a single day. During each of these jobs, he didn't stop in the middle and say, "well boys, the rest of this is going to have to wait. I finished my 15 reps of hay stacking, and now I have to hit the triceps extension machine and do some swiss ball crunches." You worked hard, and your body just figured out the rest.