Interval Training Builds Fitness Fast
Vary Your Training Intensity to Boost Your Performance
By Elizabeth Quinn, About.com Guide
Updated: April 19, 2009
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
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
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
Intensity (speed) of work interval
Duration (distance or time) of work interval
Duration of rest or recovery interval
Number of repetitions of each interval
Common Interval Training Workouts
Plyometric Program for Injury Prevention
30-Second Sprint Drills
Boot Camp Workouts
Explosive Exercise Training
Jump Rope Workouts
It is recommended that you consult an athletic trainer, coach or personal trainer prior to designing an interval