Interval Training Builds Fitness Fast

Vary Your Training Intensity to Boost Your Performance

By Elizabeth Quinn, 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

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


  • 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

  • Stair Running

  • Plyometrics

  • Plyometric Program for Injury Prevention

  • 30-Second Sprint Drills

  • Boot Camp Workouts

  • Speed Drills

  • Explosive Exercise Training

  • Agility Drills

  • Shuttle Runs

  • Tuck Jumps

  • Jump Rope Workouts

It is recommended that you consult an athletic trainer, coach or personal trainer prior to designing an interval

training program.