THE BIG IDEA: Set fitness goals that are in line with your time constraints.
WHY: You won't get into ultra-endurance shape if you don't have time to log plenty of long, slow miles. Following a plan of short, high-intensity workouts gets you ready for short, high-intensity performances. "You're not going to do well at an Ironman or a stage race on six hours a week," Carmichael advises. "But you'll be surprised with the results you can get at one-to-three-hour events."
DO IT: Shift your focus to sprint-distance events. Aim to set a new best time in a 10K instead of a marathon; set your sights on a local criterium or mountain-bike race instead of a century. Do as much training as you can close to your race pace. Invest time in your weak spots, not your strengths. If you're already muscular, scratch the weights. Flexible? Minimize stretching. And scale back long warm-ups and cooldowns. Ten minutes before hard interval workouts, and five after, is all your body needs.