A new study suggests your body knows best how hard to run each interval and how long to rest in between.
Written by: Matt Fitzgerald
Effective interval training depends on two factors: good planning and proper execution. Good planning entails choosing specific interval workout formats that are appropriate to your goals and current fitness level. For example, a set of 16 x 400m at one-mile race pace might be appropriate for an elite middle-distance runner in his or her peak training period, but would not be a wise choice for a modestly fit 10K runner at any point in his or her training.
Proper execution of an interval workout entails two things: 1) running the intervals as fast as possible without “bonking” before the workout is over and without unduly stressing the body, such that the runner is unable to recover adequately for the next hard workout; and 2) taking the minimum amount of recovery time between intervals to sustain maximum performance in the intervals throughout the workout. If you don’t rest long enough between intervals, you will start to slow down in the later intervals and you won’t get as much out of the workout as you should. And if you rest longer than necessary between intervals, the workout will not be as challenging as it ought to be and again you won’t get as much out of it as you could.
There are various tools that runners can use to ensure that they rest enough, but just enough, between intervals. One such tool is a heart rate recovery target, where the runner waits until his or her heart rate has slowed to a certain level after an interval before starting the next. A second tool is a predetermined work-rest ratio. Past research has demonstrated that runners generally recover after intervals of a given length and intensity in predictable amounts of time. These known patterns can be used to fix work-rest ratios for each workout that the runner then adheres to. This is the most commonly used method that attempts to ensure a runner gets enough, but just enough, rest between intervals.
A third tool that can be used for this purpose is perceived readiness. As the term connotes, this method entails jogging or walking after completion of an interval until the runner simply feels ready to perform the next at the same level.
In an interesting new study, researchers from Australia’s James Cook University compared the effects of these three ways to set recovery duration in interval workouts. Eleven male competitive runners performed a given interval workout on several occasions. Each time they were instructed to run the intervals at a predetermined level of perceived effort. But they used different recovery guidelines in different sessions. They used a heart rate recovery target in some, adhered to a fixed work-rest ratio in others, and relied on perceived readiness in the remaining sessions.
The authors of the study, which was published in the journal Psychophysiology, reported that the runners’ interval times were slower when they used a heart rate recovery target. This indicates that the heart rate recovery target did not allow them to rest long enough. And while the runners’ interval times were comparable in the sessions in which recovery was set by work-rest ratio and perceived readiness, their actual recovery periods were shorter when they used perceived readiness. This indicates that the use of a work-rest ratio allowed the runners to rest too long.
Thus it appears that perceived readiness is the best tool to determine recovery durations in interval workouts. Now, one might argue that the other two measures could be equally reliable if the target recovery heart rate and the work-rest ratio were adjusted (specifically, in this case, if the target recovery heart rate were lowered and the work-rest ratio increased), but why bother? Perceived readiness is also the simplest of the three tools and therefore represents the “straightest line” toward the destination of effective interval workout execution.
This study is but the latest in a recent spate of studies showing that training “by feel” is superior to more high-tech and scientific ways of training—or is at least an indispensible complement to them. To learn more about training by feel, check out my new book: RUN: The Mind-Body Method of Running by Feel.
FILED UNDER: Features / Training TAGS: intervals / James Cook University / Matt Fitzgerald / Mind-Body Running / Recovery / RUN: The Mind-Body Method Of Running By Feel / Running By Feel / Work-Rest Ratio