The Benefits of Interval Training (and How It Can Improve Your VO2 Max)

Hard efforts followed by easy recovery can boost your speed and performance. Here’s how.

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There are a few good reasons why we turn to interval training to boost our speed and performance: It’s efficient; it’s rewarding, and it works.

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“A major benefit of interval training is that you can see significant results in a short period of time,” says Corinne Fitzgerald, certified personal trainer and coach at Mile High Run Club in New York City. “Just 20 minutes of intervals is enough to see changes in your cardiovascular efficiency, or your body’s ability to carry oxygen to working muscles.”

Of course, you need to train regularly to see a real difference in your race-day performance (experts say it takes five to 10 sessions spread out over a few weeks), but if you’re still not noticing any improvement—or you’re new to interval training (welcome!)—then read on for a primer.

What is Interval Training?

Interval training simply means switching between low- and high-intensity work. “Interval training taps into both the aerobic and anaerobic energy systems by alternating between short bursts of intense activity (anaerobic) and more moderate activity (aerobic),” says Caroline Geiger, certified group fitness instructor and coach at Precision Running Lab by Equinox, who teaches in the New York City and Boston locations.

In terms of running, that usually means you sprint for a certain period of time (or distance), then recover. Sprint, recover. Sprint, recover. Sprint, recover.

Easy, right? Problem is, lots of runners make the mistake of running at a more moderate pace throughout their intervals (running slightly faster, then running slightly slower to recover).

“Even trained runners may struggle to achieve the necessary intensity,” says Jill Barnes, Ph.D., an assistant professor of kinesiology at the University of Wisconsin-Madison. “But committing to the prescribed intensity during both work and rest ratios is key to maximizing the benefits of this type of training.”

Translation: Go really hard when it’s time to go hard (as in, “empty the tank” hard, Barnes says) and really recover when it’s time to recover.

What Are Other Benefits of Interval Training?

As we mentioned earlier, interval training can help you run faster. “Interval training is a core tool in improving overall speed over longer distances,” Geiger says. “If you push your body to handle an all-out pace for several short intervals, the body adapts to handle a more aggressive sustained pace over time.”

She’s right: Interval training helped trail runners run 5.7 percent faster on a 3,000-meter track test in a Journal of Strength and Conditioning Research study.

Interval training can also improve your form. “There’s less room for error when you’re running faster,” Fitzgerald says. “You naturally clean up your form to find every little bit of speed and energy you have left.” Plus, the nature of interval training forces you take a break before your form starts to break down.

And if weight loss is one of your fitness goals, interval training can help tip the scale in your favor. In fact, interval training helped people lose 29 percent more weight than moderate steady state-exercise, according to a British Journal of Sports Medicine review.

“It takes your body longer to return to its pre-exercise state after high-intensity exercise, so you burn more calories after the workout is over,” Fitzgerald says. “Interval training fires up your metabolism.”

Geiger adds: “Higher intensity workouts spike certain hormones that suppress appetite and reduce stress—and stress eating.”

How Does Interval Training Affect VO2 Max?

“VO2 max looks at the combination of how much oxygen-rich blood your heart can pump, and the muscles’ efficiency in extracting and utilizing the oxygen,” Fitzgerald says. “The more efficiently you can use the oxygen, the more efficient you become at removing lactic acid from the blood.”

This is particularly important in fast, short-distance runs. “The faster you run, the more lactic acid you build up, so your VO2 max becomes more important,” Fitzgerald says, noting that your VO2 max is most significant for short races like a 5K.

Geiger says you can improve your VO2 max through interval training for sustained periods of time at intensities at or near your VO2 max, which is roughly 90 to 100 percent of your maximal heart rate. “Consistent training at this level conditions your body to perform better under increased physical stress,” she says.

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How to Design Your Own Interval Workouts

“The best part about interval training is that you have the creative freedom to try different types of intervals,” Fitzgerald says. But if you don’t know where to start, she suggests a 1:1 ratio of running and recovery. “Run hard for two minutes, then recover for two minutes.” Or, if you prefer to go by distance, “run hard for 400 meters, then walk for 400 meters.” To improve your VO2 max, keep adding a minute until you’re working hard for six to eight minutes.

Just be sure you actually recover during the recovery periods (Fitzgerald says to let your heart rate drop to 110 to 120 beats per minute) and leave enough recovery in between each individual workout. “Interval training is taxing on your entire body,” Geiger says. “You’ll notice the best results if you interval train once a week or twice a week, and incorporate steady-state cardio, strength training, yoga or stretching, and plenty of rest into your routine.”

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