This efficiency comes with a caveat: You have to commit. You may be inclined to blow off the warm-upsOpens a New Window.. Don’t. They mobilize muscles so they can handle what’s ahead, and they’re not easy, either. Follow the instructions to the letter. If a workout calls for 16 reps, hit that exact number; if it prescribes 60 seconds of rest between sets, that’s all you get; and when we tell you to take a day off, do it. If you go all-in, we guarantee you’ll see results—and you’ll realize that getting your fittest is a whole lot easier than you thought.