Interval Training is defined as high-intensity intermittent exercise.

Interval-training sessions can be different in composition, as there are three variables that can be altered: the intensity (speed), the work period and the rest period. Whichever variable(s) is/are altered it is important to remember that you must perform the workouts to exhaustion. Interval training is about setting a demanding intensity level and working at that level for the prescribed work/rest ratios until you cannot continue. If you do that, you have reached overload and the training will be effective. Without overload, there is no adaptation and the benefits are not obtained.

The Research
Several studies show that  high-intensity cardio intervals with very short rests, is a very intense workout that maximally stresses both aerobic and anaerobic systems. Intervals with longer rest periods, does not stress both the anaerobic and aerobic energy systems as much, and so more work can be done until fatigue.

Longer rests between the intervals are more effective for anaerobic recovery training, as the body can learn to buffer the acidosis and mobilize the anaerobic enzymes during the rest period. This type of workout would be beneficial for games players, who need the ability to repeat short maximal efforts, with low-intensity recovery periods, throughout a match. 

Without question, High Intensity Interval Training is one of the most effective means available for rapidly losing body fat and improving your cardiovascular conditioning. Not only do you burn many more calories while you're performing the training, you also stimulate your metabolism to a far greater degree than with lower intensity training, which is traditionally hailed for fat loss.

Interval training is based on a very simple concept: go fast then go slow. Repeat. It sounds easy, but within this simple formula lies a tremendous number of possible variations and strategies you can employ to take full advantage of the power available to you.

Interval training can be performed on almost any cardiovascular machine (including the treadmill, stair machine, stationary bike, elliptical trainer, etc.) as well as almost any type of cardiovascular exercise (such as cycling, swimming, running, etc.).

Though the examples I will go through below use time as a measure for intervals, you can also very easily use distance as your guide.

For example, you can sprint between two telephone poles then walk to the next one. You can sprint the length of a football field then walk the width. You can even run up a flight of stairs then walk back down. The variations you can do are truly endless!

Here are a number of different types of interval training you can use:

Aerobic Interval Training is very beneficial for rapidly improving your aerobic conditioning as well as burning fat.

The rest interval for this type of training is between 30 seconds to a minute. Naturally, the shorter the rest period, the tougher the training will be. Too much rest will allow your body to recover too much, lessening the overall training effect of the exercise.

Here are some examples of a number of different intervals you can use in your training:

Work	Rest
2 min.	30 sec.
3 min.	1 min.
3 min.	45 sec.
2 min.	1 min.
5 min.	30 sec.




Example 2

Using intervals, such as the examples shown above you can choose to stick to the same time intervals (e.g. do 2 minutes hard and 30 seconds slow for the duration of the workout) or mix it up with different time intervals as you go through your session. This type of training can generally be done for about 20 to 30 minutes.

Maximal High-Intensity Intervals
Maximal Intervals are much shorter than Aerobic Intervals. Generally, the longest you'll be able to perform a maximal effort is around 30 seconds so all the work intervals are 30 seconds or less. 

During Maximal High Intensity Interval training you must push yourself to the maximum on every single work interval you do. This type of training is extremely effective when training for sports that require all-out repeated efforts, such as football, soccer, hockey, etc. If you want to get faster and recover faster, this is the type of training for you. This type of training dramatically increases the body's metabolism. Studies show that this type of training also causes large amounts of Growth Hormone (GH) to be released into the bloodstream.  

Rest periods can be short or long, depending how good of shape a person is in and/or how much they want to recover in between intervals. Shorter rest periods make the work intervals more challenging but the speed of the work will also drop quickly after a few intervals. Longer rest periods will allow the body to recover a little more, allowing faster speeds on more intervals. Rest periods should always be at least as long as the work periods. This is to allow enough recovery to be able to perform well on the next work period.


Like the first two examples given for Aerobic Interval Training, you can stick with one steady time period through the entire session, or vary your intervals. Because during Maximal High Intensity Interval training you must push yourself to the maximum on every single work interval you do, the work rest intervals will need to be shorter than those during less intense interval training. Here is an example illustrating this point: 

Work	Rest
30 sec.	30 sec.
30 sec.	1 min.
20 sec.	1 min.
10 sec.	30 sec.
30 sec.	2 min.

Here's a sample of how to do it:
Interval 1 - 30 seconds hard, 30 seconds rest.
Interval 2 - 30 seconds hard, 30 seconds rest.
Interval 3 - 25 seconds hard, 30 seconds rest.
Interval 4 - 25 seconds hard, 30 seconds rest.
Interval 5 - 20 seconds hard, 30 seconds rest.
Interval 6 - 20 seconds hard, 30 seconds rest.
Interval 7 - 15 seconds hard, 30 seconds rest.
Interval 7 - 15 seconds hard, 30 seconds rest.

This type of interval training is very similar in concept and execution to the Maximal interval style. The difference is, instead of pushing yourself as hard as you can on each work interval, you work at a pace that is somewhat below your max. This allows you to do more total work intervals during the session while still keeping your intensity levels high.

Most Interval programs on cardio machines follow this principle. The resistance/speed is increased to a higher level for a set period of time then reduced for a set period of time. The level is not so high that you must put your maximum effort into each work interval, but it is at a level you could not keep up for long periods.

This type of training is also very effective for fat loss and increasing the metabolism.

Because this type of training is not done, essentially to "failure" or "all out" the intervals can be longer than what would be used for Maximal High Intensity Interval Training..For example:


Work	Rest
30 sec.	30 sec.
30 sec.	1 min.
1 min.	1 min.
1 min.	30 sec.
45 sec.	45 sec.

This type of training can be done for about 15 to 30 minutes, depending on the intensity level of the work.

This is a unique form of interval training combines Aerobic Interval Training with Maximal Interval Training. It allows you to work at near-peak levels for long periods of time. This has the benefit of burning a tremendous amount of calories for longer periods of work time than is possible with normal intervals. How it is performed is simple: 
• The work intervals themselves are short but the rest periods are much shorter.
• Instead of pushing yourself to the max on every interval, you work at a pace somewhat short of your max. 

This type of training works very well with cardio machines that allow you to switch resistance instantly or very quickly (stationary bikes, stair machines or elliptical trainers often allow this). Machines that must cycle slowly through their speeds as they change do not work well for this (treadmills fall into this category). It can also be done with running then walking, cycling then pedalling slowly.

Example Near-Maximal Aerobic Interval Training Period

Work	Rest
20 sec.	5 sec.
25 sec.	5 sec.
30 sec.	10 sec.
15 sec.	7 sec.
40 sec.	10 sec.

No discussion of Interval Training would be complete with a reference to Fartlek Training. Translated from Swedish, "Fartlek" literally means "speed play." What is it? It's simple - Fartlek training is every type of interval rolled into one workout!

Fartlek training will allow your mind and body to be accustomed to training at higher than normal levels. This in turn means you have the chance to greatly improve your aerobic and anaerobic systems and, if required, lose weight more effectively.

Fartlek training is generally associated with running, but can include almost any kind of exercise.  Most fartlek sessions last a minimum of 45 minutes and can vary from aerobic walking to anaerobic sprinting.

The idea is to train at a wide variety of speeds, distances and times in order to hit the widest variety of training parameters.Sessions should be at an intensity that causes the athlete to work at 60% to 80% of their maximum heart rate (220-your age. E.g 220-19=201) , as outlined by the Karvonen Method. This should mean that their body will not experience too much discomfort while exercising. An athlete should also include a good warm up at the beginning of the session, and a cool down at the end of the session, to improve performance and to decrease the chances of injury and for other reasons.

• Warm up – easy running for 5 to 10 minutes.
• Steady, hard speed for 1.5-2 km; like a long repetition.
• Rapid walking for about 5 minutes – recovery.
• Easy running interspersed with sprints of about 50 – 60 m, repeated until a little tired. – Start of speed work.
• Easy running with three or four "quick steps" now and then (simulating suddenly speeding up to avoid being overtaken by another runner).
• Full speed up hill for 175 – 200 m.
• Immediately, fast pace for 1 minute.
• The whole routine is then repeated until the total time prescribed on the training schedule has elapsed.