The Art and Science of Interval Training

Written by Kristaps Petrovs, Eau Claire YMCA Strength and Conditioning Instructor

Runners at all levels should be able to utilize this mode of training and receive significant improvements in their racing times, regardless of where they finish in the pack.

Interval Training Terminology:

Interval: The recovery distance between the bursts.

Repeat(repetition): The fast burst part of interval training.

Energy System: The fuel supply systems that the body employs during various types of (intensity) of exercise.

Anaerobic: Fast, high intensity exercise where you cannot supply enough oxygen to the working muscles and consequently have to stop slow down.

Aerobic: Steady state exercise where you take in enough oxygen to supply the muscle’s demands. This would be running at a pace you can maintain for a long time.

Benefits of Interval Training:

Improves Competition. It stimulates the stress of race pace and conditions athletes for competition

Improves Neuromuscular Coordination. Your nervous system gets used to running at a faster pace.

Less lactic acid accumulation at a given pace. It trains the athlete to run faster and train their body to accumulate less lactic acid at a given pace.

Thermoregulatory system is not as stressed. Body heat does not accumulate as rapidly as during continuous running.

Runners of all abilities can use it. Interval training can benefit almost any healthy person, from beginning exercisers to world-class endurance athletes.

Interval Training–You run shorter bursts faster than you would run a race, with much slower recovery intervals between these fast bursts. This how you get the name “Intervals”.

With recovery intervals, we eventually adapt to sustaining the workload for a longer period.

By manipulating the length of the recovery interval we create the desired training effect. For example, short recovery intervals create an oxygen debt, so we improve faster.

To find your level of performance you need to take the following factors into account: the acronym is DIRT:

D Distance of each fast burst

I Interval, or length of recovery jog or walk between fast bursts

R Repetitions. How many fast bursts we do in one session.

T Time for each fast burst.

Most runners go wrong by using incorrect distances for their fast bursts and/or recovery distance, then wonder why they aren’t improving their times, or their times are getting even slower.

Here are some key guidelines to using intervals successfully:

  1. It’s important to exercise the right energy system your competitive racing distance stresses. Your fast bursts need to be the correct distance for your main racing event.
  2. It’s critical you recover completely between interval sessions so your energy reserves are replenished and your muscle tissue has time to recover and rebuild.
  3. Don’t do too many fast interval bursts in each workout.
  4. Experiment with adjusting your recovery interval to get the desired training effect for your racing distance.
  5. Interval training should not become your focal point of your weekly training program. You don’t want to become over competitive with yourself and obsessed with your interval times.
  6. Establish your limitations with all of the above.

Finding the Right Energy System for your Interval Sessions

Three energy systems can be stressed with interval training:

  1. Adenosine Thriphosphate-Phosphocreatine (ATP-PC) System if you’re training for very short-term fast energy release activities of less then 10 seconds (like 100m sprints).
  2. Lactic Acid System, which primary uses glucose as it’s energy source, for events lasting 1-3 min. (such as 400m-1500m).
  3. Aerobic System which uses oxygen as its catalyst for energy release while burning fats and carbohydrates in events that last longer than 3 min.

Unless you are a sprinter, the ATP-PC system is not worth using in your training. The lactic acid system becomes more important because middle distance runners stress it when they compete. But the main system recreational and semi-serious runners utilize is the aerobic system, they should be between 3-10min.

How to estimate the speed of your fast Interval bursts?

The longer the fast bursts, the slower they need to be because of our limited ability to supply oxygen to the working muscles and to disperse fatiguing byproducts (such as lactic acid) as they build up. So, if you do mile repeats, do them 10-25 sec. faster than your average 5km race pace.

Once you reach 8 or 10x400m repeats comfortably, for example, you can pick up your pace by about 2-3 seconds for following sessions.

General advice for doing your interval workouts.

Many runners waste their time doing 100-400m bursts and wonder why their times don’t improve. They’re not exercising the right energy systems for their racing distance. However, you will get benefits from doing shorter interval bursts. You’ll improve your neuromuscular coordination of running at high speed, which will help you run faster in your races. The disadvantage of shorter faster intervals is that as intensity increases, so do your chances of injury because of the higher impact.

The length of your interval bursts.

Because of the precise nature of the distances and times you’ll be running, interval training is best done on 400m track. How far you should be running in your fast bursts? Distances that stress the aerobic system include 800m (2 laps), 1200m (3laps), 1600m (4laps), and even 2000m (5laps).

How many fast bursts should you do in an interval workout?

The cumulative distance of the fast bursts in your interval workouts should add up to 1,5-2 miles for beginners. For example, a session of 8x400m should be the absolute maximum number prescribed, and that would not be recommended for your first interval workout. You might start with 4 repeats of 400m, adding 2 to that workout next time you do it.

What to do in the recovery intervals?

Walking or jogging, or a combination of the two, is recommended in the interval between your fast bursts. Your first goal is to adapt to the interval workouts by attaining the maximum number of repetitions over these distances. Then, for continued improvement, speed up the fast bursts, or decrease the recovery interval between them.

Decreasing the length of the recovery interval between fast bursts achieves great results, because this does not allow your energy sources (ATP and glucose) to completely resynthesize.

Thus you draw on the emergency back up system, the lactic acid system. Your body adapts to this by tolerating smaller amounts of lactic acid, enabling you to cruise at much faster pace with less lactic acid building up.

How much time is needed to recover from an interval workout?

It’s critical for you to adapt your interval workouts rather let them exhaust you because of the high risk of illness or injury. Allow at least 48 hours between these high intensity workouts, and if you’re over 30 years old, one interval workout a week is sufficient. Your muscles, tendons, ligaments, and connective tissue need much longer to recover past this age, as they lose their elasticity and resilience.

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