Five Rules for Losing Body Fat With Sprint Intervals

The BEST exercise method to lose body fat and shrink your waistline is interval training in which you do hard but short bursts of exercise. These workouts save you time, and they are varied so you aren’t bored.

One reason intervals are so effective for changing your body is that they tap into the anaerobic energy system. You improve your conditioning so you can tear up a flight of stairs without passing out, but you also improve your metabolism, train the nervous system to work better, and build muscle.

This potent combination of changes makes it your go-to training mode for fat loss. Because it’s so effective, there are numerous popular workouts available. You can do everything from track sprints, to circuit weight training, to flipping tires and running with sandbags.

The good news is that compared to aerobic exercise in which you just plod away endlessly, anaerobic workouts more consistently promote fat loss, especially from “stubborn” areas like the stomach and belly. Here are five rules for making anaerobic-style training work for you:

#1: Limit workouts to less than 30 minutes.

Workouts should last between 10 and 30 minutes depending on intensity. Any workout longer than 30 minutes is NOT an anaerobic interval workout.

If you’ve still got energy and motivation left in the tank after 30 minutes, you’re not working hard enough.

If you think you’re superhuman, and this doesn’t apply to you, consider that the stress hormone cortisol tends to increase with long-duration workouts to tap into fuel sources from muscle in order to provide continued energy to keep you going. This situation is not conducive to fat loss.

#2: The hard intervals of your workout should last 10 to 40 seconds.

There’s some flexibility here, but novices should start with longer, slightly less intense intervals of 30 to 40 seconds, whereas more advanced trainees will benefit from doing both longer and shorter, all-out 10 to 30 second intervals.

This model can be used for both sprint workouts on a track, bike, or elliptical, or when training with weights or bodyweight exercises.

For instance, you could do Tabata intervals of 20-seconds on, 10-seconds rest with bodyweight exercises. Or try the powerlifts (deadlifts, squats, and bench press) for 6 to 10 reps per set, carefully controlling the down motion with a 4-second count.

#3: The rest period should be active and last 10 to 90 seconds.

You may think the purpose of the rest period is to avoid passing out, but there’s actually a method to the madness that is informed by how the body regenerates energy and deals with waste products produced during intense exercise.

Therefore, novices will benefit from starting with a more equal exercise to rest ratio, in between those slightly less intense 30 to 40 second intervals.

Once you’re ready for all-out intervals, try starting with a work-to-rest ratio of 1 to 4 and then, over a period of weeks, tapering to a 1 to 2 and then 1 to 1.5 ratio.

So, say, you were doing 200-meter sprints that take 30 seconds, you’d rest 2 minutes for the first few workouts, eventually reducing the rest to 60 and then 45 seconds.

Active rest, such as walking or jogging, is optimal for enhancing resynthesis of phosphocreatine fuel stores and removing the buildup of waste like hydrogen ions.

#4: Make sure the hard parts of your workout are truly HARD.

Being able to physically push yourself is a skill. So, if you’re new to interval training, you may need to work on this.

It’s recommended you either get a trainer to push you, get an experienced workout partner, or at the least, try a small group class taught by a savvy trainer.

Studies testing “hardness” or “rating of perceived exertion” suggest that trainees typically rate anaerobic workouts in the 8 to 9.5 range on a 1-to-10 scale with 10 being extremely hard.

Shoot for an 8 or 9 and make your hard parts so hard that you can barely make it to the rest period. If you feel like you’re going to die, but you’re not dizzy or about to throw up, keep going and remind yourself that “it’s temporary.” Know that the human body was born to do this.

A useful trick for reducing how hard it feels is to decrease the duration or intensity of work bouts as you progress.

For instance, a study of athletes found that when they did a sprint workout in which they decreased sprint distance (400, 300, 200, 100 meters), it felt easier than when they increased distance from 100 to 400 meters as the workout progressed.

#5: Try two workouts-a-day for a little while for faster fat loss.

Just like fat loss should not be an all the time goal (plan it, do it, and move on), two-a-day workouts shouldn’t be used indefinitely, but they are useful to accelerate fat loss over a few weeks.

You can do weights in the morning and intervals in the afternoon, or do one short interval workout (less than 25 minutes each) in the morning and another in the evening.

This is not the sort of thing that is ideal if you have a highly stressful job or life situation, or are just generally busy. It’s not a solution to poor nutrition or bad sleep either.

Two-a-days are ideal when you have some down time in your life and can give extra energy and focus to your body.

Now, if you’d like more guidance in figuring out which interval workout is best for your unique self, check out this article that details specific protocols for different conditioning levels.

If you don’t like sprinting and want to lose fat by lifting, read this article that reviews a few high intensity weight workouts to get a killer physique.