Running is a proven fat blaster, but to incinerate calories even more efficiently, try taking things up a notch with all-out speed bursts. “Sprinting turns your body into a furnace,” notes IFBB figure pro Erin Stern, a two-time Olympia champ. Unlike just going out for a steady-paced run, sprint repeats force your body to work hard and then recover, ratcheting up your metabolism so you continue to burn more calories for hours after your workout is over.

Although it’s most effective to do sprints outside on a track, you can also do them indoors on a treadmill. Regardless of where you run, form does make a difference, since speed bursts incorporate slightly different mechanics than more endurance-based runs. “The key is to remain explosive and powerful,” Stern says. As you run, remember to swing your elbows back far and bring them forward to about chest height without letting them cross your body. Keep your shoulders relaxed and your arms close to your sides. Stay on the balls of your feet, rather than striking with your heels.

Sprints can be intense, so you need to make sure you’re warmed up before you go full speed ahead, Stern warns. Start with a light jog for three to five minutes, then add in some dynamic drills to get your muscles and joints ready for action. Follow Stern’s own warmup and sprint program to maximize your results. But remember, speed intervals also call for ample recovery time, so give yourself a recovery day after a sprint workout and limit them to no more than twice a week.

Erin’s Sprint Routine

Warmup: Run 1 or 2 laps (400–800 meters) on a track or five minutes at an easy pace on the treadmill.

Dynamic flexibility drills: You can do the following moves outdoors on flat, level ground or in the gym near the treadmill.

● Leg swings: Stand tall with hands at sides. Swing right leg forward and back; do 10 reps. Switch sides and repeat. Then swing right leg out to side and back to center; do 10 reps per leg.

● High knees: Lift alternating knees in front of you to hip height, exploding off balls of feet and using arm momentum.

● Butt kicks: Move forward quickly, driving heels toward butt; keep knees pointed down toward ground and arms at sides.

● Accelerations: Run about 50 meters (⅛ lap, or about 30 seconds on a treadmill), gradually gaining speed as you run so you’re in a full sprint by the end. Repeat.

Sprint Workout
Sprint 100 meters, rest 40 seconds, 5 reps
Rest 3–5 minutes
Sprint 100 meters, rest 40 seconds, 4 reps
Rest 3–5 minutes
Sprint 100 meters, rest 40 seconds, 3 reps
Cooldown: 5-minute walk/jog, stretch

Note: If you’re running on a treadmill, sprint for about 20 seconds. Challenge yourself to go at a faster speed than you’re typically used to—aim for 10 mph. Use a timer to help keep track of the intervals.