Workout Speeds

from "VO2MAX Newsletter by Jason Karp

One of the biggest mistakes runners make is running workouts at speeds that are either too fast or too slow to obtain the desired result.   Problem is, they don't know what the desired result is.   To determine the correct speed, you must know the purpose of each workout.   Is it to improve lactate threshold?   VO2max?   Anaerobic capacity?   Muscle power?   Technique?   Each one of these variables requires a different speed that will optimize the workout.

Each of the next few newsletters will focus on a specific type of workout and discuss the correct speed for that workout.   Having begun with easy and long runs last month, we continue this month with lactate threshold (tempo) runs.  

The lactate threshold, or what I often call the acidosis threshold (AT), demarcates the transition between running that is purely aerobic and running that includes significant oxygen-independent (anaerobic) metabolism and the development of acidosis.   Therefore, AT is the fastest speed that you can sustain aerobically.   The purpose of AT training is to raise the aerobic ceiling by increasing the speed at which the pace becomes anaerobic.   As you can imagine, this takes time.

As a coach, I've noticed that the AT workout is the most difficult type for runners to run at the correct speed since it requires holding back and not pushing the pace.   There's a comfortably hard feeling to the pace that requires practice.  

AT pace is about 10 to 15 seconds per mile slower than 5K race pace (or about 10K race pace; 75 to 80 percent max heart rate) for recreational runners and about 25 to 30 seconds per mile slower than 5K race pace (or about 15 to 20 seconds per mile slower than 10K race pace; 85 to 90 percent max heart rate) for talented and highly trained runners.   The better your endurance, the longer you can hold your AT pace and the better you'll be at sustaining any fraction of your AT pace.   Running much faster than AT pace is not any better than running at AT pace.

Recovery Intervals

from "VO2MAX Newsletter by Jason Karp

While the focus of interval workouts is almost always on the work periods--how fast, how long, how many repetitions--the reason they are called 'interval workouts' or 'intervals' is because of the recovery interval between work periods.   When interval training was first studied in the 1950s, the belief was that the primary stimulus for cardiovascular improvement occurs not during the period of activity, but during the recovery interval.   The original interval training method incorporated periods of effort ranging from 30 to 70 seconds at an intensity that elevated the heart rate to about 180 beats per minute.   The effort phase was followed by sufficient recovery time to allow the heart rate to return to 120 beats per minute, signifying the readiness to perform the next work period.

During the recovery interval, the heart rate declines at a proportionally greater rate than the return of blood to the heart, resulting in a brief increase in stroke volume (the amount of blood the heart pumps with each beat).   The increase in stroke volume places an overload on the heart muscle, which makes the heart stronger, and enables the skeletal muscles to be cleared of waste products quickly due to the elevated rate of blood flow when there is little demand for activity from the tissues.   Since stroke volume peaks during the recovery interval, and because during an interval workout there are many recovery intervals, stroke volume peaks many times, providing a stimulus for improving maximum stroke volume and thus the capacity of the oxygen transport system.

Also during the recovery intervals, a portion of the muscular stores of runners' quick energy--adenosine triphosphate (ATP) and creatine phosphate (CP)--that were depleted during the preceding work period is replenished via the aerobic system.   During each work period that follows a recovery period, the replenished ATP and CP will again be available as an energy source.

You can monitor your heart rate during the recovery intervals either by wearing a heart rate monitor or the old-fashioned way by palpating your carotid or radial artery and counting pulses for 10 seconds and multiplying by 6.