Aerobic Interval Training

Aerobic Interval training is my favorite type of cardio workout.  My description of it in this post is based primarily on the teachings of (1) my high-school track coach and (2) the personal trainer I hired after my first baby was born. 

Note: Make sure you read these precautions before attempting any type of exercise: Exercise Precautions.

What is Interval Training?

Interval training is basically short bursts of high-intensity exercise (e.g., sprinting, running, fast walking, etc. – depending on your ability) followed by periods of recovery (e.g., easy walking, etc.).  You don’t have to run/walk for interval training.  You can do repeated high-intensity bursts on a stationary bike, an elliptical machine or in a swimming pool.  For example, if you are on a stationary bike, simply pedal on a higher level for 2 minutes, then take it down to a lower level until you recover. 

If you belong to a gym, most cardio equipment (e.g., treadmills, ellipticals, stationary bikes, etc.) has interval training programs built in. You can choose these programs to simplify things.  That said, you may already be doing interval workouts!  Either way read on to find out the benefits.

What are the Benefits?

All exercise lowers the risk of heart disease, protects against Type 2 Diabetes and can result in weight loss.  However, interval training offers the following specific benefits:

• Increases Cardiovascular Fitness Quickly
• Raises the Body’s Potential to Burn Fat[i]
• Makes workouts less boring as things are constantly changed up!

How Does Interval Training Achieve the Above Benefits?

• Interval training allows someone to spend more total minutes at a higher intensity than they could in a single sustained effort.
• The high-intensity periods cause your body to build extra muscle fibers to support what your body thinks is going to be a sustained physical exertion. This enhances the body’s ability to metabolize fat and carbohydrates.[ii]
• Interval training stimulates a change in your mitochondria (the body’s cellular powerhouse where fuel is converted to energy). This change causes your mitochondria to burn fat first – even during easy interval training workouts. Additionally, burning fat first also allows you to workout longer, because it takes longer for your body to need to tap into your carbohydrate stores.[iii]

How is it Done?

Generally interval training workouts should consist of a five-minute warm-up, 4-6 cycles of high-intensity/low-intensity, and a five-minute cool down.  The high-intensity period should be enough to make you out of breath and last about 1-4 minutes.  Some experts say that a person should reach 80-85% of their maximum heart rate in this phase.[i]  The low intensity period should last as long as it takes for you to regain your breath. 

An interval workout may look something like this…

• Warm up with a Brisk Walk – 5 minutes
• Run – 2 minutes
• Walk – 2 minutes
• Run – 2 minutes
• Walk – 2 minutes
• Run – 2 minutes
• Walk – 2 minutes
• Run – 2 minutes
• Walk – 2 minutes
• Run – 2 minutes
• Walk – 2 minutes
• Cool down with a Brisk Walk – 5 minutes

Total Workout = 30 minutes

If someone is in great shape, it will take them less time to recover (say, one minute).  Additionally some people choose to run faster for less time.  Doing both will make a workout significantly shorter. 

If you are interested in having an interval training workout tailored to your needs, you should sign up for a session with a personal trainer.  It will only take one session to get the information you need… although they will probably try and sign you up for more.  A personal trainer can calulate your resting heart rate, maximum heart rate, resting metabolic rate, etc., and take a more scientific approach to meeting your needs.

How Often Should it be Done?

Interval training can be done 1-2 times per week.  Any more often and your body will not have sufficient time to recover.  Your body needs 24-48 hours to recover from an interval training workout.

[ii] Journal of Applied Physiology Two weeks of high-intensity aerobic interval training increases the capacity for fat oxidation during exercise in women  http://jap.physiology.org/cgi/content/abstract/102/4/1439

[iii] A Healthy Mix of Rest and Motion, New York Times http://www.nytimes.com/2007/05/03/fashion/03Fitness.html