What is Interval Training

With so many workout styles to choose from, are you wondering what is interval training. Is it just another fad? 

Does it really work? It seems every month there is a new fitness craze taking the country by storm. But, high intensity interval training (HIIT) is one concept that has been around for many, many years. Quite simply, interval training is a combination of both high intensity and low intensity cardiovascular exercises.

Basically, a high intensity interval (known as a Sprint Interval) will be followed by a lower intensity interval (known as a Rest Interval). During rest intervals – or periods of recovery – you will not stop your activity, but rather slow it down to allow your body time to recover from the challenge of the sprint interval. 

HIIT at Every Level

The length of the intervals will depend on your fitness level and the type of sprint activity. The intensity level refers to how hard you actually push yourself during the sprint interval. This can be different for each person.

For example, if you are a beginner, moving from a brisk walk to a slow jog may really get your heart pumping. However, if you are a trained athlete, it may take a full-out run to raise your heart rate to the same level. The type of activity can also make a difference.

If you are an experienced runner, you may have to push your body harder to reach your target heart rate than you would if you were trying out a new type of exercise such as boxing or kettlebells. Scientifically (or biologically) speaking, interval training combines two types of exercises: Aerobic and Anaerobic.

The Science of HIIT

Basically, your body has two different systems that it uses to produce energy. During aerobic exercise, your heart and lungs are able to provide enough oxygen to meet the demands being put on your muscles.

In other words, oxygen is used to break down glucose and create fuel for your body. So, you inhale and your body uses the oxygen to power your muscles. This process creates carbon dioxide and water, which you will release when you exhale.

When breathing provides enough oxygen to produce the energy needed for your muscles to perform, this is called aerobic respiration. For most aerobic activity, oxygen is used to create the fuel needed for prolonged activities (such as running, walking, rowing, etc.).

This is not a bad thing, because when your body is in this stage, you are burning more calories. Plus, since you have used up stored energy, your muscles will need to replace what was lost.

This means that you will continue to burn calories even after you are finished your workout. However, during periods of intense exercise, the energy needed exceeds what can be provided by breathing.

Your muscles begin to experience oxygen depletion and now your body must work without oxygen. This is called anaerobic respiration. In fact, “anaerobic” means “without oxygen”. Since your muscles do not have enough oxygen to meet the energy demand they must now create glucose by breaking down stored glycogen. 

For you science buffs, this process is called glycolysis. Instead of Carbon Dioxide and water, anaerobic respiration produces a substance called lactic acid. Lactic acid is what causes the muscle burn you experience during a hard workout.

It is also responsible for the fatigue and muscle soreness you may have after putting a lot of strain on your body (such as repetitive action, overtraining, or doing something your muscles may not be used to). Unfortunately, lactic acid isn't as easy to get rid of as CO2 since you cannot simply breathe it out. This is one reason why high-intensity exercises should be kept to short bursts.

Aerobic and Anaerobic Exercises Together

Aerobic exercises can be performed for long periods of time; however, anaerobic exercises should be done for short periods only due to the demands they put on your body. This is what makes HIIT so perfect. You can get the benefits of both aerobic and anaerobic exercises.

Plus, the slower, lower intensity intervals will allow your body to carry the lactic acid out of the muscles before it has a chance to build up or pool. Taking the time to cool down and stretch after a workout will also get rid of the lactic acid in your muscles so you can reap the benefits without all the side-effects. Since interval training uses both of your body's energy producing systems, there are many benefits to this type of exercise.

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HIIT Benefits

HIIT offers a lot of proven benefits, but it isn't for everyone. If you have a chronic health condition, are new to exercising, or are recovering from an injury, consult your doctor before beginning an interval training plan.

Anaerobic intervals are very challenging and you need to monitor your heart rate carefully. Like any form of exercise, start out slowly and increase the intensity as your fitness level improves.

Other pages that might interest you:

I will continue to share ideas about diet and exercise that have helped me along the way. If you have any questions I can help you with, or if you have any ideas you want to share, feel free to contact me or visit our Q&A forum.

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