Let’s face it: Only a small percentage of us (like, say, that percentage of us currently training for a triathlon) really love cardio. For most, it seems like a hopeless slog. Now research has figured out why: It is a hopeless slog … when you plod. For a study published in the January 2011 issue of Medicine & Science in Sports & Exercise, researchers divided a couple dozen male and female subjects into two workout groups. One group did steady-state cardio for 30 to 60 minutes three times a week. The other group ran four to six 30-second all-out sprints three times a week. Wanna guess who crushed more calories? Surprise! The second group. Their workouts elevated their metabolic rates for a longer period, resulting in twice the burn. The effects on maximum cardiac output remain unknown, but the take-home is simple. Next time you step on the treadmill, jack that speed to the max.