Interval training: Can it boost your calorie-burning power?

Interval training is a powerful tool for novice exercisers and accomplished athletes alike. Here's how it works.

By Mayo Clinic staff

Are you ready to shake up your workout routine? Do you wish you could burn more calories without spending more time at the gym? Consider aerobic interval training. Once the domain of elite athletes, interval training has become a powerful tool for the average exerciser, too.

What is interval training?

It's not as complicated as you might think. Interval training is simply alternating bursts of intense activity with intervals of lighter activity.

Take walking. If you're in good shape, you might incorporate short bursts of jogging into your regular brisk walks. If you're less fit, you might alternate leisurely walking with periods of faster walking. For example, if you're walking outdoors, you could walk faster between certain mailboxes, trees or other landmarks.

What can interval training do for me?

Whether you're a novice exerciser or you've been exercising for years, interval training can help you jazz up your workout routine. Consider the benefits:

• You'll burn more calories. The more vigorously you exercise, the more calories you'll burn — even if you increase intensity for just a few minutes at a time.
• You'll improve your aerobic capacity. As your cardiovascular fitness improves, you'll be able to exercise longer or with more intensity. Imagine finishing your 60-minute walk in 45 minutes — or the additional calories you'll burn by keeping up the pace for the full 60 minutes.
• You'll keep boredom at bay. Turning up your intensity in short intervals can add variety to your exercise routine.
• You don't need special equipment. You can simply modify your current routine.

How will my muscles respond to interval training?

During intense exercise, muscles produce waste products that can contribute to muscle soreness. Too many accumulated waste products can make exercise painful and exhausting. But by alternating bursts of intense exercise with easier intervals, you'll help reduce the buildup of waste products in your muscles. The result is more comfortable exercise.

Are the principles of interval training the same for everyone?

Yes — but you can take interval training to many levels. If you simply want to vary your exercise routine, you can determine the length and speed of each high-intensity interval based on how you feel that day. After warming up, you might increase the intensity for 30 seconds and then resume your normal pace. The next burst of more intense activity may last two to three minutes. How much you pick up the pace, how often and for how long is up to you.

If you're working toward a specific fitness goal, you may want to take a more scientific approach. A personal trainer or other expert can help you time the intensity and duration of your intervals — which may include movement patterns similar to those you'll use during your sport or activity — based on your target heart rate, the ability of your heart and lungs to deliver oxygen to your muscles (peak oxygen intake) and other factors. This type of interval training also adds variety to your workout, but it requires more discipline and concentration.

Does interval training have risks?

Interval training isn't appropriate for everyone. If you have a chronic health condition or haven't been exercising regularly, consult your doctor before trying any type of interval training.

Also keep the risk of overuse injury in mind. If you rush into a strenuous workout before your body is ready, you may hurt your muscles, tendons or bones. Instead, start slowly. Try just one or two higher intensity intervals during each workout at first. If you think you're overdoing it, slow down. As your stamina improves, challenge yourself to vary the pace. You may be surprised by the results.

Interval Training Builds Fitness Fast

Vary Your Training Intensity to Boost Your Performance

By Elizabeth Quinn, About.com Guide

Updated: April 19, 2009

About.com Health's Disease and Condition content is reviewed by the Medical Review Board

Interval training has been the basis for athletic training routines for years. The first forms of interval training, called "fartlek" involved alternating short, fast bursts of intensive exercise with slow, easy activity. Fartlek was casual, unstructured training that perfectly fit its English translation: "speed play."

What is Interval Training?

The interval programs of today have become highly sophisticated methods of structured training for athletic performance enhancement. Physiologists and trainers have designed interval programs that are specifically suited to individual athletes. These sessions include precisely measured intervals that match the athlete's sport, event and current level of conditioning. Often the appropriate intensity and duration of the intervals is determined by the results of anaerobic threshold testing (AT) that includes measuring the blood-lactate of an athlete during intense exercise.

How Interval Training Works

Interval training works both the aerobic and the anaerobic system. During the high intensity effort, the anaerobic system uses the energy stored in the muscles (glycogen) for short bursts of activity. Anaerobic metabolism works without oxygen. The by-product is lactic acid, which is related to the burning sensation felt in the muscles during high intensity efforts. During the high intensity interval, lactic acid builds and the athlete enters oxygen debt. During the recovery phase the heart and lungs work together to "pay back" this oxygen debt and break down the lactic acid. It is in this phase that the aerobic system is in control, using oxygen to convert stored carbohydrates into energy.

The Benefits of Interval Training

This repetitive form of training leads to the adaptation response. The body begins to build new capillaries, and is better able to take in and deliver oxygen to the working muscles. Muscles develop a higher tolerance to the build-up of lactate, and the heart muscle is strengthened. These changes result in improved performance particularly within the cardiovascular system.

Interval training also helps prevent the injuries often associated with repetitive endurance exercise, and they allow you to increase your training intensity without overtraining or burn-out. In this way, adding intervals to your workout routine is a good way to cross train.

According to the American College of Sports Medicine, more calories are burned in short, high intensity exercise. If you are counting calories burned, high intensity exercise such as intervals are better than long, slow endurance exercise, but you may pay a price. Read more about the benefits and dangers of high intensity exercise.

You don't need to be a world-class athlete and have sophisticated blood analysis to take advantage of the benefits of interval training. The standard "speed play" training of fartlek works well for the rest of us. This type of interval work is based upon your subjective needs. Simply pay attention to how you feel and set your intensity and duration accordingly.

Interval Training Safety Tips

• Warm Up before starting intervals
• Assess current conditioning and set training goals that are within your ability
• Start slowly. (for example: walk 2 minutes/ run 2 minutes) In general, longer intervals provide better results
• Keep a steady, but challenging pace throughout the interval
• Build the number of repetitions over time
• Bring your heart rate down to 100-110 bpm during the rest interval
• To improve, increase intensity or duration, but not both at the same time
• Make any changes slowly over a period of time
• Train on a smooth, flat surface to ensure even effort
• You can also use circuit training as a form of interval training

Advanced Interval Training Workouts
You can take a more scientific approach to interval training by varying your work and recovery intervals based on your pre-determined goals. Here are the four variables you can manipulate when designing your interval training program:

• Intensity (speed) of work interval
• Duration (distance or time) of work interval
• Duration of rest or recovery interval
• Number of repetitions of each interval

How to Do Interval Training

By eHow Sports & Fitness Editor

Introduction

To tap into a new, higher level of fitness and fat burning, try an interval workout. The combination of aerobic and anaerobic training will give a real boost to your health and make the rest of your workouts seem easier.

Instructions

Difficulty: Challenging

Steps

1

Step One

Begin with 5 to 7 minutes of low-intensity work in your exercise mode. For example, walk or jog lightly to start.

2

Step Two

Stretch the major muscle groups, paying particular attention to the lower body.

3

Step Three

Exercise at a higher intensity for 10 minutes. Let your body continue to warm up and get ready for the workout to come.

4

Step Four

Start cycle 1: Exercise for 3 minutes at a pace you could maintain for the entire workout. Then for 1 minute push yourself hard, with a short burst of activity that you couldn't do for longer than a minute.

5

Step Five

Recover for 30 seconds or longer, but keep moving, and let your breath return to a normal workout level.

6

Step Six

Understand that the cycle is 3 minutes aerobic/recovery and 1 minute anaerobic (3-to-1).

7

Step Seven

Complete eight cycles, the first four becoming progressively harder, with the hardest cycles being four and five, then decrease the intensity with cycles six, seven and eight.

8

Step Eight

Keep moving for another 3 to 4 minutes or until you feel your heart rate coming down.

9

Step Nine

Stretch the major muscles again, this time more deeply and for 20 to 30 seconds.

Tips & Warnings

• Always use the first 30 seconds of the aerobic portion to recover and literally catch your breath.
• Think of the cycles as going up and down a mountain - as they ascend, it's hard and there's not much oxygen at the top, then the descent gets easier.
• Note that 1 minute may be too long for a beginner, so try shortening the anaerobic (without oxygen) cycles - even 10 seconds is an effective way to start.
• Notice that your heart rate is going way up and then way down; it should peak and valley quite a bit during interval training.
• Plan to interval train only once or twice a week.
• Allow for 48 hours of recovery between each session. It's OK to exercise during the 48 hours, but avoid strenuous exercise and anything high-impact.
• Drink lots of water.
• Please consult your physician before attempting this or any other strenuous physical activity. Listen to your body.
• This advice is not intended to substitute for advice from a physician, physical therapist or personal trainer.

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