Is it possible to have the best of everything? Interval training workouts can last as little as 20 minutes, perfect for time-strapped people. You work very hard, doing multi-muscle exercises (often with weights), alternating cardio with strength training. Because the workout is short, it’s easy to stay motivated. You’ll work up a sweat (if you don’t, you’re doing something wrong!), but your hair won’t be exposed to sweaty scalp for very long, so hair recovers easily. As a bonus, research has demonstrated that short, intense cardio and strength-training interval workouts whip your body into shape for power, toned muscles and cardiovascular fitness as well as longer workouts and better than less-intense workouts.