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What Are the Benefits of Interval Training?

Are you pressed for time? Are you interested in improving your aerobic capacity and exercise performance in less than one-fifth the time of traditional endurance training? If so, then interval training is just what the exercise physiologist ordered. Indeed, research proves that you can improve your endurance and recovery from intense bouts of exercise with just one hour per week of interval training compared with five hours per week of traditional endurance training.

Athletes know the magic of intervals. They use them all the time to improve their performance, and they know that intervals help speed up recovery so they can get going quickly after a blast of energy (like a sprint). In this article, we will review what interval training is, describe the benefits and the studies that prove it works, and I’ll show you how to design an interval-training program.

There are several advantages to interval training:

  1. Fitness and performance improve quickly with interval training, typically in just a few weeks. I’ve known athletes who reported an improvement in speed after just two interval workouts.
  2. Recovery time improves with interval training. Recovery is critical for athletes in sports like tennis, basketball, soccer or hockey, where the sport demands continuous stops and starts, or an endurance bike ride or road race where you hit hills and need to catch up quickly at the top in order to keep your pace. You’d never perform well if you sprinted all-out or climbed a hill and then needed two minutes to recover (also known as sucking wind). It would never work.
  3. Research confirms that interval training improves fitness similarly to traditional aerobic training in much less time.
    • In one study comparing interval training to traditional training, subjects increased their fitness and the activity of many of enzymes that contribute to using oxygen efficiently with two and a half hours of intervals over two weeks compared with 10 and a half hours of traditional endurance training over the same time period.
    • In another study comparing the two methods of training, subjects increased the use of stored glucose (glycogen) and fat by the same amount after five days a week of training for six weeks, but the interval subjects trained only one and a half hours per week compared with four and a half hours per week for the endurance subjects.
    • Some interval training schedules can be too rigorous. In a study of subjects who did interval training every day for two weeks, the oxygen capacity increased, but anaerobic capacity did not. The investigators suggested that this was due to overtraining and exhaustion from daily interval sessions.
    • To reduce the effects of overtraining, investigators had subjects perform six, two and half-minute interval sessions over a two-week period, with one to two days of rest in between sessions, to promote recovery. Interval sessions consisted of four to seven “all-out” 30-second sprints on a stationary bike with a total of four minutes of recovery. This training regimen increased fat burning and doubled endurance capacity with just 15 minutes of intense cycling over a two-week period!

Interval sessions are tough, and you must “dig down deep” to find the motivation to push yourself, but the payoff is big. Find a training partner if you need help pushing yourself. Commitment to a partner will get you out the door when you don’t feel like it, and a little healthy competition never hurts to increase performance.

What is a high intensity interval training (HIIT) workout?

Interval training is a method of training where you increase and decrease the intensity of your workout between aerobic and anaerobic training. Interval training in Sweden, where some say it originated, is known as fartlek training (Swedish for “speed play”).

The protocol for interval training is to push your body past the aerobic threshold for a few moments and then return to your aerobic conditioning level with the objective of improving your performance (speed, strength, and endurance).

The aerobic threshold is the intensity where your body switches from burning a greater percentage of fat to a greater percentage of carbohydrate and is generally 85% of your maximum heart rate (train below 85% and it’s considered aerobic exercise; train above 85% and it is considered anaerobic exercise).


Cropped shot of a young woman working out with a barbell at the gym


How are interval-training sessions designed?

Interval training can be personalized to the individual in almost every facet. The idea is to set up work to active-recovery ratios (work:active-recovery) in intervals of minutes.

For instance, let’s say you usually train comfortably at 6 mph on the treadmill. So, after your warm up and a few minutes at 6 mph, you sprint for one minute at 7.5 mph and then jog again at 6 mph for three minutes (1:3 ratio: a total of four minutes). You continue these intervals for your entire workout and then cool down for about five minutes.

How do I determine how hard to work?

Heart rate is a good indicator of how hard you’re working, and it’s easy to measure, so it’s an ideal method for setting up and monitoring intervals. Here’s an example. Say your heart rate is 70% of your predicted maximum when you jog at 6 mph. After you warm up and spend a few minutes at that pace, you increase the speed for your work interval to 7 mph, which might be 85% or even 90% of heart rate max, and then you cut back on the speed to 6 mph at a heart rate of 70% of max for your active-recovery.

Below is a sample 28-minute interval workout (excluding warm-up and cooldown). Keep in mind that you can spend the entire workout doing them or vary it and do just some of the work intervals, and note that the time of each interval in this example always adds up to four minutes.

Sample HIIT Workout

  • Warm-up: five minutes at 5-6 mph
  • Interval 1: three minutes at 6 mph (70% of max heart rate)
  • Interval 2: one minute at 7 mph (80% of max heart rate)
  • Interval 3: three minutes at 6 mph
  • Interval 4: one minute at 7 mph
  • Interval 5: three minutes at 6 mph
  • Interval 6 – harder: one minute at 7.5 mph (85% of max heart rate)
  • Interval 7: three minutes at 6 mph
  • Interval 8: one minute at 7.5 mph
  • Interval 9: three minutes at 6 mph
  • Interval 10: one minute 7.5 mph
  • Interval 11: three minutes at 6 mph
  • Interval 12: one minute 7.5 mph
  • Interval 13: three minutes at 6 mph
  • Interval 14: last push — one minute at 8 mph (90% of heart rate max)
  • Cool down: five minutes at 5-6 mph, then walk

Some athletes train as high as 100% of heart rate maximum. We don’t recommend that beginners go above 85%-90%, and 1:3 work:active-recovery ratios are the standard starting point. Remember to stay well-hydrated during the entire exercise.

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