This article was originally published here.

Interval training is an effective method for getting your body used to a variety of paces. Read on for more information.
1. A Bit Of History

The training method known as "interval training" was devised by two German physiologists in the 1930s. They envisioned a type of running which would take into account the quantity and especially the quality of runs. In the 1950s, Emil Zatopek, who won "triple golds" (in the 5k, 10k and marathon in the 1952 Olympics), started to train with and disseminate the method of interval training. Soon after, a racing game called Fartlek (comprised of fast sprints of varying, random lengths) was invented by Gösse Holmer, a trainer for the Swedish team.
2. What Is Interval Training?

Interval training is a method consisting of several repetitions at regular intervals during a training session. These consist of accelerations, recovery phases and returning to regular intensity. No matter your level or goals, interval training will help you improve your endurance.

Interval training can be adapted for the individual pace and abilities of every runner. You can modify the intensity and level of your interval training depending on how you feel. The main goal of interval training is to gradually increase your vVO2max, which the maximum aerobic speed you can sustain without causing physical harm to your body.

Interval training is a very interesting way to break up the monotony of training and re-motivate yourself to run. This training approach has numerous benefits. Whether you are a novice or a more experienced runner, you can improve:

- your physical abilities (both in terms of muscle strength and cardiorespiratory fitness);

- your endurance and running power;

- your running technique (movements, strides, etc.).

Short, medium or long sessions will become easier on both a physical and psychological level.
3. Why Choose Interval Training? How Does It Work?

If you are considering interval training, you are probably interested in improving your physical health, increasing motivation, making progress as a runner and maybe even medalling at a competition.

You already know that interval training is not only for champions trying to achieve higher and higher levels of performance!

Interval training in running changes your pace and is an effective way to improve your physical abilities. Basically, if you always run at the same pace, your body gets used to it. At first, you make progress, but then, you start to stagnate a bit, since your body becomes accustomed to the physical activity regular running sessions entail. Training sessions without alternating pace do not allow your body to develop new physical abilities.

To increase endurance and performance, you need to surprise your body by forcing it to adapt to different paces when you run. Interval training consists of varying your speed and is an ideal way to make gains and feel great when running. There are two major categories of interval running :

- Aerobic paces promote your respiratory abilities in order to provide the maximum amount of oxygen to your muscles. (Aerobic paces are used during interval training.)

- Anaerobic paces are much faster and cannot be sustained for long distances, since this kind of effort does not provide enough oxygen to the muscles to be sustained for long periods of time.

Road or trail runners use "aerobic interval training" when considering their fastest pace or maximum aerobic speed. Your vVO2max is the fastest speed you can run at while still providing enough oxygen to your muscles.

When you start interval training, things shouldn't be complicated!

Simply speed up for a short period of time and build in a recovery period after each change of pace.

Training sessions will become more fun and much more comfortable.
4. Choosing Your Interval Training Sessions

It's not always clear how to decide between shorter or longer interval training sessions. We recommend modifying your training based on the length of your run and its characteristics (ground conditions, temperature, etc.). If you are preparing for a 10k or a marathon, we recommend 3 types of endurance training sessions:

Active endurance training is calculated in periods of 12, 8, or 6 minutes at 80 to 88% of your maximum heart rate (HRmax). The best way to do this type of training is to accelerate your pace for 4 sessions of 6 minutes per session. Make sure to take one solid minute for recovery in between each faster session.

Long-distance endurance training consists of 3 to 4 faster periods of about 1200 metres each followed by 400 metres of slow jogging to recover. You should be at 90 - 95% of your max heart rate.

Short-distance endurance training is a type of endurance training composed of ten 300 metre sprints, each of which is followed by jogging for 100 metres to recover. Your maximum aerobic speed is calculated based on a distance of 2000 metres, the reference distance for calculating vVO2max. 

Interval training: Accelerate, recover, improve