In the last installment of “Stride Fast, Stride Right”, we looked at why building aerobic power is important. Here we will look at the importance of Interval Training in the process, and the positive adaptations that can occur as a result of this specific type of training. Near the end is an example workout that illustrates the following points:

VO2 Max Intervals
At the core of any well designed workout is the intention to stress a particular physiological system of the runner. To gain aerobic power, intervals, specifically VO2 Max intervals, are key to implementing the necessary stress that ultimately causes a boost to your cardiovascular fitness. VO2 Max stands for “maximum oxygen consumption”. The goal then of these intervals is to raise the cardio system’s maximum ability to use ingested oxygen.

Why intervals?
One of the main focus’ within an interval workout is to spend time at your proper VO2 max intensity, which is described as 95-100% of your maximum ability over the distance you are running. It has been found (for most runners) that an optimal amount of total time to spend within a workout at VO2 intensity is 12-20 minutes. However, it would be extremely difficult for a runner to run continuously at their VO2 pace for this duration of time! To attempt to do so would most likely result in the athlete slowing down, which would result in a lowering of the heart rate to a sub-optimal level. This would cause the intention and focus of the workout to be threatened!

Consequently, to allow for the proper amount of stress at the intensity, the workout is broken up into intervals (which last 2-5 minutes in duration). These intervals will allow the runner to repeatedly achieve the desired level of intensity within the correct time frame (12-20 minutes) while allowing for rest in between each interval.

Rest intervals are very important in VO2 Max training! These rest periods occur between each “active” (run) interval, and they should be long enough to allow the runner to be able to complete each successive interval at the same intensity as the previous one. Thus the runner would be able to meet the intention of the workout: 12-20 minutes of total time spent at their VO2 intensity.

Common interval distances
Common distances for interval workouts range from repeats of 400 meters through 1 mile.

Example workout
To illustrate the information above, we can look at a runner who is able to attain their maximum heart rate by running 800 meter intervals in 3:00 for each interval. Based upon the above, an appropriate workout would be 4 – 5 x 800 meters, with full rest in between each interval. This would give the runner a total of 12 – 15 minutes of running at their VO2 pace, helping them to achieve a high quality workout that will boost their cardiovascular fitness.

Adaptations
Running at such an intensity is challenging! However, here is where the necessary adaptations occur that allow for an increase to your cardio fitness. At its basic level, the human body responds to safe, repeated and APPROPRIATE stress by repairing itself and coming back stronger. With high-intensity interval work, the human lungs become stronger by being able to handle a higher amount of oxygen intake, and the increased strength of the heart allows it to increase its stroke volume, i.e. more blood is allowed to be pumped with fewer contractions.

Next time we’ll be giving some shout-outs and look at some runners within the UA family who have gained success in their races from 5k through the marathon through steady use of VO2 Max interval training.