We’ve heard from trainers that a slow, 30 minute jog isn’t an effective workout; we’ve also seen spreadsheets and charts describing 30-minute workouts that involve sprinting, jogging, and even short walks. So what really happens to your body when you run long vs. short distances, at a slow or fast pace? To find out, we asked Derek Peruo , a personal trainer at Peak Performance in New York City who writes and consults for magazines like Men’s Fitness, Muscle & Fitness, and Men’s Health. We asked him about everything from calorie-burning to metabolism—and even things like V02 max, muscle building, and the elusive runner’s high.
Read the gallery to find out what really happens to your body during different types of runs—and what kind of training plan is best for you: