Posted: August 19, 2005

Science of Sport: Things Momma Never Taught You About Recovery Intervals

By Owen Anderson, Ph. D. (Copyright © 2004-2005)

Much attention is paid to the nature of the work intervals within interval workouts. Coaches, athletes, and exercise scientists worry about the time duration of work intervals, their intensity, the number of work intervals per training session, and so on. Meanwhile, much less attention is devoted to the recovery intervals, even though they often comprise as large a portion of the overall workout (from a time standpoint) as the bouts of hard effort.

Most coaches and athletes do recognize that recovery-interval length is a key variable associated with the improvement of interval-workout quality. For example, a time-honored principle in interval training calls for a gradual reduction in the lengths of recovery intervals. If an athlete starts a specific training period using four-minute work intervals at 5-K pace, with four-minute recoveries, one reasonable progression within the period is to gradually pare the recoveries down to a lower limit of 30 to 60 seconds, while holding steadfast with the work intervals. Such recovery-interval trimmings raise the overall quality of the workout: average percents of VO2max and vVO2max both rise as recoveries are abridged, and blood-lactate levels tend to soar.

Another time-honored interval-training precept is that the 1:5 ratio is optimal when work intervals are carried out at an extremely high intensity (1:5 simply means that recovery lasts five times as long as work; for example, if an athlete completes each work interval in 25 seconds, the recovery between work efforts would be 125 seconds).

The rationale for 1:5 during close-to-maximal interval training has always seemed reasonable. It is well-known that potent bursts of powerful running cause major upturns in muscle acidity. In theory, the floods of hydrogen ions which pour into the muscles must be buffered before another bout of high-intensity running can be carried out at top speed, and this buffering takes time. Using long recovery intervals, about five times as long as the work periods, should be about right, according to conventional thinking.

The reasoning behind 1:5 also depends on the energetics of muscle contraction. Run as fast as you can for 20 seconds, for example, and your natural muscle levels of ATP, the key high-energy compound which must be available in order for your muscle cells to contract, reach an all-time low. Similarly, intramuscular concentrations of phosphocreatine, a chemical which donates high-energy phosphates to ADP to create the absolutely essential ATP, also bottom out after a bout of close-to-max hustling. Phosphocreatine re-synthesis, like buffering, is not an instantaneous process, and thus we have the 1:5 ratio, which appears to provide a generous amount of recovery time. Incidentally, the role played by phosphocreatine during high-intensity interval training helps to explain why creatine supplementation boosts the quality of intense interval workouts; high creatine intakes tend to raise the muscles’ natural concentrations of phosphocreatine and therefore make it more difficult for phosphocreatine to be drastically depleted during searing running efforts.

But is 1:5 really a good ratio? Bear in mind that if your planned workout is 8 X 100 in 14 seconds each (just to pick some numbers), with 70-second recoveries (using the 1:5 ratio), and your first five intervals are on target but your sixth, seventh, and eighth efforts all fall considerably short of the proper pace, the 1:5 ratio is probably not the proper choice. Longer recovery intervals would probably enhance the quality of work intervals six, seven, and eight. For very high-intensity interval training, the basic idea (in most cases) is to use the recovery interval length which permits the highest-quality training. You are not trying to raise average oxygen consumption rate for the workout, you are trying to enhance your coordination at high speed and boost your maximal running velocity. Running at lower fractions of your current max pace will not get the job done as well, compared with hanging in there at just a nip under max.

Recently, J. Lakomy and D. T. Haydon of the University of Southampton in the United Kingdom took a systematic look at what happens to athletes when they use the 1:5 ratio during very high-quality interval training (1). 18 elite male field-hockey athletes who were members of a Premier National League field-hockey team took part in an initial investigation in which they completed an intense 6 X 40-meter interval workout, using maximal effort. Average times for the 40-meter sprints ranged from about 5.8 to 6.1 seconds, and 30-second recoveries were utilized between work intervals, so the work-rest ratio was very close to 1:5.

An interesting aspect of this study was that in one trial there was no deceleration zone – the athletes could take as much space as they needed to slow down gradually after their 40-meter efforts. On a separate date, however, the athletes had to rapidly decelerate to a stop within six meters of the end of each 40-meter sprint. Sprint times and fatigue levels were then compared for each condition.

The reason for this methodology was that the athletes were field-hockey players, and field hockey is a game in which participants sprint at close-to-max pace for 20 to 40 meters at a time and then make sudden stops or changes in direction. Adding the six-meter deceleration zone for one of the trials was an effort to mimic this situation. The researchers hypothesized that the use of the deceleration zone would heighten fatigue during the workout (because both the quads and hamstrings would have to work feverishly in an eccentric manner to produce the very sudden stops; the quads would eccentrically stop spring and the hams would eccentrically have to limit swing). In theory, this fatigue would manifest itself as slower work-interval running over the final work intervals of the session. Although this might seem bad, it would actually be good, because the slowing would reveal that high-quality interval training for field-hockey players should include deceleration areas, to more closely mimic the specific, fatigue-producing demands of the sport.

Interestingly enough, the utilization of the deceleration zone did not have a huge impact on the quality of the work intervals. For example, the average times for the six 40-meter sprints in the deceleration and control trials were not significantly different. However, the second work interval was significantly slower than the first when the deceleration area was used (this was not the case when no deceleration zone was present), indicating that the fast-slow-down area was quickly inducing some measure of fatigue during the workout. The overall lack of effect (of deceleration on average sprint times when the two six-sprint trials were compared with each other) may simply have been due to the fact that the workout was so short. Many endurance runners (and sprinters) would scoff at the idea of calling it a day after just six 40-meter repeats. Indeed, the English researchers were able to show, using statistical techniques and linear extrapolations, that work-interval times for the deceleration runners would have been slower beginning with the 11th interval of the workout.

For most of us, however, the really interesting results in this study related to the quality of the intervals. Were these elite, well-trained athletes able to maintain the same work-interval intensity over all six work intervals while using the vaunted 1:5 ratio?

In a word, no: There was a significant slowing of work-interval speed over the course of the six intervals. As mentioned already, the second interval was already slower than the first when the deceleration zone was used. With no deceleration zone, work intervals four through six were significantly slower than work interval one. In short, use of the 1:5 ratio did not permit work-interval quality to be sustained.

This is not surprising. Although we hear “1:5” from the lips of a variety of experienced runners and coaches, at least three other scientific investigations have shown that the use of 1:5 is associated with a significant decay in running performance over the course of a very high-intensity workout (2, 3, & 4).

Of course, this is not necessarily a big deal to field-hockey players, as well as soccer, basketball, and lacrosse participants. They are constantly stopping and starting during their games, and so they want to mimic that situation in their workouts, the basic goal being to enhance the ability to run pretty fast in the face of high levels of fatigue. However, note that the “5” may actually be too long for such competitors, from the standpoint of matching the physiological demands of training with the requirements of real-live competitions. 1:1 or 1:2 (or – dare we think of it – 2:1 or 3:2) may be better for such sportsmen/sportswomen, since such ratios more closely mimic what really happens in games.

The shortcomings of 1:5 are a big deal to sprinters and endurance runners, of course, who do not stop and start within their competitions. They are looking not for a workout which optimizes their ability to sprint for six seconds and cruise for 30 seconds, over and over again, but for one which optimizes maximal running velocity. And when a runner creates a workout which is designed to heighten maximal running speed, it makes no sense at all to put together a session which will guarantee sub-par running during a significant fraction of the work intervals. Unfortunately, 1:5 seems to do just that.

Rather, it makes sense to use the following simple rule: Recover for as long as is necessary to complete each work interval in the planned manner. This might mean using 1: 7, or it might mean utilizing 1:20 or even 1:30 – it doesn’t matter. For these high-speed workouts, we are looking to develop the neuromuscular capacity to improve maximal running speed, which is an important predictor of both sprint and endurance performances. Dragging through the final intervals of a session won’t cut it; we want to do all of our intervals at that fine edge which forces those reluctant nerves and muscles of ours to improve their functioning. With max-running-speed-improving sessions, we are not trying to hoist average oxygen-consumption rate – we are trying to run faster. If grandiose recovery intervals allow us to do that, we should violate the 1:5 principle and utilize fat recoveries without a moment’s hesitation. ©

A follow-up note from your tireless editor: At this point, you may be thinking: “When should I do these max-speed-enhancing workouts, what specific pace should I use, how long should the work intervals be, and how many work repeats should I complete?”

It is important to bear in mind that these max-velocity-hoisting sessions should be completed throughout your training year. Running speed is not something which can be developed by micro-pipetting an array of anaerobic enzymes into your muscle cells; the improvement of maximal running velocity is to a large extent a neuromuscular phenomenon which can take a considerable amount of time to accomplish. Greater speed depends on greater force production when the foot is on the ground, quicker force production, and greatly improved stability and coordination (so that the newly developed forces can be used for propulsion rather than the stabilization of an out-of-control body), and these things are not developed in a day – or even during a traditional six-week period of “speed training.”

Naturally, the max-speed-boosting workouts you use at the beginning of your year will be quite different from the ones you utilize toward the end, when your strength and power have expanded considerably. A good start, during your first few weeks of training, would be something like (2-4) X (60-100), with whatever recoveries you need to run at the same speed during each work interval. The pace to use is simply your maximal pace, but you should not strain and tighten up as you run: Relax and flow along smoothly, while attempting to run as quickly as possible, maximizing force production with each foot impact while simultaneously keeping contact times very short. Note that a workout like this is so short that it can be included within your warm-up before a quality workout or even carried out on an easy day (after you have warmed up, of course). The only time not to do it is after a fatiguing workout: Remember that max-speed workouts depend on coordination and quick force production, which are hampered by neuromuscular fatigue.

Toward the end of your training year, as your key 400-meter, 800-meter, 1500-meter, 3-K, 5-K, 10-K, half-marathon, marathon, or ultra-marathon competition approaches, you will have worked up to something like 15 X 60, 12 X 100, or 8 X 200, all completed with “flying starts” (don’t begin the work intervals from a standing-still position), all at close to max speed, and all with as much tasty recovery as you need to preserve power. ©

References

(1) “The Effects of Enforced, Rapid Deceleration on Performance in a Multiple Sprint Test,” Journal of Strength & Conditioning Research, Vol. 18(3), pp. 579-583, 2004
(2) “Physiological Responses to Maximal Intensity Intermittent Exercise,” European Journal of Applied Physiology, Vol. 65, pp. 144-149, 1992
(3) “Cycling and Running Tests of Repeated Sprint Ability,” Australian Journal of Science & Medicine in Sport, Vol. 25(4), pp. 82-87, 1993
(4) “Effect of Recovery Duration on Performance during Multiple Treadmill Sprints,” In: Proceedings of the First World Congress on Science and Football 1987. pp. 134-144, London: E & F. N. Spon, 1988

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