Surely many have heard such a thing as “interval running”. It is one of the fundamental workouts in any middle to long distance running program. Let’s figure out what interval running is, how to conduct it correctly, and what it is for.
What is interval running
In simple words, interval running is a type of running that is characterized by a change in fast and slow pace. For example, they ran 3 minutes at a fast pace, then started running for another 3 minutes, but at a slow pace. And as a rest, it is better to use slow running, and not walking. Why this is so will be discussed below. There is also a very similar type of training that the famous American running coach Jack Daniels, on the basis of whose research I am writing this article, calls repetition in his book “800 meters to a marathon”. It runs about the same. Only the speed of running segments during such training is higher, and the distance of the segments is less. In general, the essence of training is similar. However, interval training is primarily designed to improve MOC. And repeated training develops, first of all, the speed of overcoming the distance.
What is interval training for?
As I said, interval training primarily develops MR. That is, the ability of the body to saturate the muscles with oxygen, which, in turn, must also process this oxygen well.

Accordingly, the higher the athlete’s MPC, the more efficiently his body will process oxygen, which is the main source of energy when running long distances.

Features of interval training
1. The body begins to work at the level of the IPC in about 2 minutes. Therefore, the duration of each high-speed segment must be more than 2 minutes or see point 2.

2. If you perform shorter intervals, for example, one and a half to two minutes, then you will still train the MPC, but only due to the fact that the body will not have time to fully recover during the rest, and with each new interval you will be faster achieve the required level of MIC. Therefore, for the development of maximum oxygen consumption, both short intervals, 400-600 meters, and longer ones, 800, 1000 or 1500 meters, if the latter does not exceed 5 minutes. In this case, the tempo of the intervals, regardless of their length, will be the same.

3. When running at the IPC level for more than 5 minutes (of course, the average figure), the body begins to go into the anaerobic zone, which is not needed when training the IPC.

4. Recovery between intervals should be active, that is, slow running, not walking. The graph below, which is taken from Peter Jansen’s book Heart Rate, Lactate and Endurance Training, shows that active recovery reduces the level of lactic acid in the muscles many times faster than passive rest. This, by the way, is a scientific explanation for what to do after a workout.
5. The time of slow running between intervals should not be longer than the time of running the high-speed section. For example, if you run 1000 meters in 4 minutes at the IPC level, then you need to rest for 3-4 minutes. But not longer.

6. The speed of the interval training should be such that your heart rate will be close to the maximum. You don’t need to increase the speed.
Fartlek as a type of interval training
Fartlek is one of the most famous types of interval training, it is especially actively used for weight loss. All the principles that apply to regular interval work apply to the fartlek. The only difference is that during the fartlek, alternations of running at a pace below the pace at the IPC can also be added. Namely, you perform one interval at the level of the IPC, that is, almost at the maximum heart rate. Then do a standard rest in the form of a slow run. Then proceed to the interval at the so-called threshold pace. This is the pace at a heart rate of 90 percent of the maximum. It develops endurance. Then you rest again.
In general, fartlek can also be performed and only at the IPC intervals.

How to include interval training in the program
Interval training is one of the most difficult in the entire training process. Therefore, you should not perform the total number of intervals more than 8-10 percent of your weekly mileage. And include interval training every week. These can be standard intervals or fartleks. In winter, it is better to perform fartlek. Since in this case you are not tied to the stadium, and you can run along any route convenient for you.