Starting a workout tired.
You won’t be able to perform to the best of your abilities. You won’t see results.
If you simply can’t get more sleep, try hitting the gym when you’re most awake. If that’s first thing in the morning, go then. Lunchtime? Grab a sandwich on your way back to work. If going to the gym when you’re most awake just doesn’t work with the rest of your schedule, grab some caffeine. Several studies have found that around 100 milligrams of caffeine (a cup of coffee) will perk you up and improve your strength.