The Hardest Upper-Body Circuit You Will Ever Do—and You Don’t Even Need Weights

You may not need equipment, but you will need a ton of willpower and stamina Thirty minutes. That’s all I’m asking for. If you can give me that, you’re going to get the best upper-body workout of your life. But here’s the deal: You can’t just go through the motions. Or start strong, and then taper …