Races - Places, you can modify the training stimulus by altering the length, number and pace of your hard efforts. In this issue, we discuss the other critical factor during interval workouts: the optimal amount of recovery between intervals.
The appropriate amount of recovery between higher intensity running during an interval session depends on the goals of the workout. There are three basic types of interval workouts: 1) cruise or lactate threshold intervals (typically one to two miles) run at about 15K to 10-mile race pace; 2) VO2 max intervals (typically 600 meters to one mile) run at about 3K to 5K race pace; and 3) speedwork (typically 200 to 400 meters) run at about 800 to 1500m race pace. Most interval sessions are variations on one of these patterns.
The optimal ratio of hard running time to recovery time depends primarily on how intensely you run the intervals and only secondarily on the length of the interval. Thus, cruise intervals, which require only a modest amount of recovery time (e.g., 30 seconds to two minutes) because the intensity is only moderately high, have a relatively high work to recovery ratio, about 5:1 to 12:1. VO2 max intervals are shorter but faster than cruise intervals with relatively longer recoveries (e.g., 90 seconds to three minutes), resulting in a work to recovery ratio of 1:1 to 2:1. Because shorter repetitions to improve your speed are run at an even higher intensity, the recoveries are comparatively long, with a work to recovery ratio of 1:2 to 1:4.
Regardless of the goals of the workout, the objective of the recovery interval is to allow you to complete the planned session at close to the desired pace. During your workout, you may need to fine-tune your pace or your recovery time. It is more productive to slow down slightly or increase the rest between hard efforts to enable you to complete the session than to cut your workout short due to insufficient recovery.
I learned this lesson shortly after college, during a workout of 800s in 2:10 to 2:12 with Bill Rodgers and his Greater Boston Track Club colleagues. I had handled this pace before, with a slow 400 meter recovery jog. The difference this day was that Bill was doing a 200 meter jog between efforts. After the fourth repetition, I was toast because of the short recovery. The error I made was to do someone else’s workout rather than to adjust the pace or the recovery to my personal ability.
Within your own limits, however, you will provide a stronger training effect from a session of VO2 max intervals or cruise intervals by keeping your recovery as brief as possible. The stimulus to improve your VO2 max (using VO2 max intervals) or lactate threshold (using cruise intervals) is provided by the amount of time that you accumulate in the optimal intensity range during a workout. Because it takes time for your oxygen consumption to increase to the correct range during an interval (over one minute during VO2 max intervals), you will accumulate more time in the most effective intensity zone by running longer intervals. Longer recoveries will allow you to run more intervals, but the more complete your recovery is the longer it takes to increase your oxygen consumption to the right level during the next interval. You need to find the optimal balance for you, between keeping the recoveries long enough to complete the workout versus short enough to provide the desired training effect.
Running Shoes - Gear?
There are two schools of thought on whether your recovery time should increase as the workout progresses. The classic approach is to jog the same amount of time (e.g., two minutes) or distance (e.g., 400 meters) after each interval. The physiology-based approach is to start the next hard effort when your heart rate goes down to a certain level (typically 120 beats per minute), with the rationale that this is a signal from your cardiovascular system that you are ready for the next interval. This approach allows you to have more rest as you become more fatigued, which improves your ability to complete the workout, whereas the set recovery time approach is arguably better preparation for racing, in that the workout gets considerably harder toward the latter stages.
My view is that you should start the workout with a set recovery distance and time (e.g., 400 meters in two minutes), and allow yourself to jog your recovery more slowly, if necessary, to complete the workout. You control the recovery time, and will know if you are being too soft on yourself, just like in a race.
Shoes & Gear?
The benefits of keeping moving during recovery include: 1) increased clearance of lactate from your muscles and blood; 2) helping your muscles stay warm and loose; and 3) keeping your oxygen consumption somewhat elevated so less time is required to get up to the optimal zone during the next hard effort. If you are too tired to jog during your recovery, then you are probably running your intervals too hard. It is not unusual to need to stand or walk for a few seconds after a 1200 meter effort at 3K race pace, but you should try to break into a jog as soon as possible to enhance the recovery process.
