Training Plans - How to Do Intervals?

INTRODUCTION

What we runners commonly call intervals should actually be called repeats. Badly reputed and feared, as if they themselves were to blame for something terrible. They are very useful for improving race performance, but unfortunately they are often done too fast, which makes them ineffective and needlessly toughens the workout. With this article I will try to help you perform this type of training better, so that you end up enjoying and even “wanting” them.

Interval training (or repeats) are nothing more than broken-up workouts, or pace workouts, done after a warm‑up of 20’ to 25’ at an easy jog. At a physiological and cardiovascular level, intervals are done to improve aerobic power, anaerobic power, and muscular endurance and strength.

In intervals not only the paces matter, recoveries are also very important. Normally, for training long distances, recoveries should be short, between 30’’ and 2’.
Personally, I recommend recovering at a very easy jog, to avoid heart rate dropping too much. Recovery will be 30’’ to 45’’ when doing short and very short distances at moderate paces; it may be 2’ when doing long intervals over 3 km, and 1’ for medium distances between 800 and 2000 m.

THE RECOVERY INDEX

Thanks to recoveries we can know our fitness level and also whether we are doing intervals correctly or not. How so? Very simple: the more beats you recover in one minute, the fitter you are. For example, if after finishing at 192 bpm, after one minute you drop to 128, then you are very fit. On the other hand, if after finishing at 184 bpm you only drop to 155 after one minute, then you are not in good shape, or you executed the interval poorly by going too fast. This is the most valuable metric when training with a heart‑rate monitor: the recovery index.

I consider “recovery index” the numerical value assigned to the beats recovered in one minute after an intense interval workout. More recovery means a higher index. Every 10 beats add one point to the index.

Example Recovery Index (beats recovered in 1’).

• 10 beats: recovery index 1.
• 20 beats: recovery index 2.
• 30 beats: recovery index 3.
• 40 beats: recovery index 4.
• 50 beats: recovery index 5.
• 60 beats: recovery index 6.
• 70 beats: recovery index 7.
• 80 beats: recovery index 8.

Interpretation:
Indexes 7 and 8 correspond to elite athletes in peak shape. Indexes 5 and 6 to sub‑elite runners or very fit recreational runners. Index 4 to well‑trained recreational runners. Index 3 to recreational runners with little experience or moderately trained. Index 2 to poorly trained runners or those starting their training season. And index 1 to runners who are just starting out.

WHAT INTERVALS ARE FOR

With workouts at varied and broken‑up paces, improvements are faster, more consistent and more evident than doing only easy runs and jogs. Those who think intervals are synonymous with pain and agony do so because they have always done them wrong, very wrong! They probably run long intervals at paces meant for short ones, making them very “painful”.

We must begin with a premise that should be very clear for all runners: when we train, we do not destroy ourselves, we only teach the body. Running intervals faster does not lead to greater improvement; on the contrary, it only results in performing far below the potential and level at which that runner is training. It is a wasted effort, an energy drain that often leads to frustration and pain. That does not mean interval training requires no effort—of course it does!—but always far from exhaustion and agony.

The proper paces in intervals depend on each runner’s race times and goals. Pace intensity is the key to any type of training. There is no use following a plan to the letter if you fail in execution because the intervals are done too fast or too slow. There is a mistaken belief that intervals should be done all‑out from the start. Some elite runners may do that at times, but not always. A recreational runner must focus on improving without suffering in intervals.

TYPES OF INTERVALS

Table to determine the type of interval workout

Explanation of the table:

• At hard intensity, closest to the pace we want to race at, aerobic power is fully developed. This requires working with long intervals (from 2,000 m to 4,000 m), controlled paces, and pace changes.
• At very hard intensities, that is, slightly faster than race pace, anaerobic capacity is developed. This is achieved by training medium‑distance repeat intervals: from 1,000 to 1,500 m.
• At maximal intensities, all‑out workouts over very short distances develop anaerobic power. These are the shortest intervals, from 200 m to 600 m. They help improve the ability to run with oxygen debt and to withstand the fatiguing effect of lactate. As long as workouts are done between 80% and 95% of maximum heart rate, greater improvements can be achieved.

Intervals by DISTANCES

Long intervals:
Over distances of more than 2,000 meters. Few reps are done; the longer the distance, the fewer the reps, and vice versa. They will add up to between 9 and 12 km, depending on the race distance being trained for. They are done at race pace or slightly easier.

• Example 1: 2 x 5,000, rec.: 2´ (two repetitions of 5 km, with a two‑minute jog recovery between each).
• Example 2: 3 x 3,000 rec.: 90´´ (three repetitions of 2 km, with a 90‑second jog recovery between each.

Medium intervals:
Over distances of less than 2,000 m and more than 800 m. The number of reps will depend on the race distance being prepared. The total mileage will range between 8 and 10 km. They are run faster than race pace.

• Example 1: 9 x 1,000 rec.: 1´ (eight repetitions of one thousand meters, recovering one minute jogging between each).
• Example 2: 5 x 2000, rec: 1’. Five repetitions of two thousand meters, recovering one minute jogging.

Short intervals:
Over short distances, less than 600 m. This is when the most reps are done. The total will range between 4 and 8 km. At paces much faster than race pace.

• Example 1: 15 x 300, rec.: 45’’ (fifteen repetitions of three hundred meters, recovering forty‑five seconds jogging).
• Example 2: 2 x 7 x 400, rec.: 50’’ y 2’ (two sets of seven repetitions of four hundred meters each, recovering two minutes between sets and fifty seconds between each rep).

MIXED intervals

Done over all kinds of distances, from 200 m to 4,000 m. They range between 7 and 9 km. They help bring training closer to race conditions. They are done at different paces: long reps similar to race pace, medium reps a bit faster, and short reps even faster.

• Example 1: (3x200)+ (2x400)+ (1000)+ (2x200)+ (3.000) + (3x300)+ (500) rec.: 2´ y 1´ (seven sets with several reps each, three reps of two hundred meters, two reps of three hundred, one of one thousand, two of two hundred, one of three thousand, three of three hundred and one of five hundred; recovering two minutes between each set and 45 seconds between each rep).

HILL intervals

Done on terrain with different gradients, at high or maximal effort. If the hills are long, the slope should be moderate. If the hills are short, the slope should be steep. Hill intervals build greater muscular power. They are mainly done in the first phase of the training plan.

• Example 1: 10 x 300 uphill rec.: jog down.
• Example 2: 2 x 7 x 80 rec.: walk down. Two sets of seven repetitions, about 80 m long.

PACE CHANGE intervals

This is the part of training where we interrupt steady running to work at higher paces, but in shorter periods, with light jogging recovery. They consist of playing with different speeds, in random times and distances, while still running. They are pace changes at variable speeds. They are done as an intermediate step between easy runs and intervals, in the second phase of the training plan. They are more effective on varied terrain with gentle hills.

TIME‑based intervals

As with pace changes, all other types of intervals can be done by time instead of distance. They can be done this way when training in an unfamiliar place where you don’t know the distances. You look for an equivalent time based on the average pace you needed for each rep. In this case, progression is guided by the heart rate monitor.
Time‑based intervals are usually done at the beginning of the second phase of the training plan, as a previous and intermediate step before distance‑based intervals. They help you better understand your sensations when running at high paces. Psychologically they cause less fatigue and are easier to complete.

• Example 1: If you had to do 9 x 1000, you can change it to 9 x 4’. In this case, in the first rep you should start at 75 or 80% of maximum heart rate, finishing the last one at around 90 or 95% of maximum heart rate.

HOW TO DO INTERVALS

It is not necessary to run all reps hard; the ideal is to start easy on the first and finish the last one the strongest. Results should be expected in the medium and long term. We cannot think that by training hard one week we will be at our peak the next.
Only after several months of systematic work do the first signs of clear progress begin to appear.

Progressive intensities

It is very important to run intervals progressively, as they are better absorbed; the joints and tendons suffer less; the muscles do not overload as much; the liver works less and more efficiently; recovery is faster and, above all, it strengthens us psychologically.
Our body has selective memory, as it remembers the last part of each workout, so doing just enough and progressively helps you improve more safely, faster and farther with less effort, and above all enjoying the run.
You may wonder how to do this; I will explain it with a simple example. If a runner wants to do 6 reps of 1000 meters at an average of 4’, what they should do is start around 4’15’’ and finish around 3’45’’ or 3’40’’. If they do it and recover correctly, it means the paces were appropriate. If it was hard to finish at those intensities and recovery was poor, it means those paces were too fast and should be adjusted down for the next intervals. But if they could not finish at those times, and even did the last two or three slower, it means they were very wrong about the paces they should run. Most likely their average pace was 5’’ to 10’’ seconds slower than initially planned.

INTERVAL PACES

Interval paces to race faster than 3’30’’ per km

Intended for runners who complete a weekly average of about 100 km, with maximums of 115 and minimums of 90. They train 6 sessions, of which two, and sometimes three, are interval sessions. The interval paces or intensities should range within the times of the following table:

Interval paces to race under 4' per km

Suitable for runners who train 5 days a week, with two of those days dedicated to interval workouts. The weekly mileage would average around 75 km, with maximums of 90 and minimums of 65. They usually race around 4'00" per km in the half marathon and between 3'50" and 3'45" in distances under 10 km.
The interval paces and recoveries between them that these runners should follow fall within the times shown in the following table:

Interval paces to race under 4' 30" per km

For runners who train 4 days a week, of which 1 or 2 days are interval sessions. Weekly mileage would be around 60 or 65 km, with maximums of 75 and minimums of 50 km.
In the following table I propose paces for runners who usually race between 4'25" and 4'20" per km in the half marathon and between 4'10" and 4'00" in distances under 10 km:

Interval paces to race under 5' per km

Training plan of 3 to 4 days per week, with only one interval day per week. The weekly mileage will average around 55 km, with maximums of 65 and minimums of 40 km.
In the following table I suggest the intensities at which the respective intervals should be run. These are paces for those racing between 5'00'' and 4'50'' per km in the half marathon and between 4'45'' and 4'35'' in distances under 10 km: