Posted: June 3, 2005

Science of Sport: What To Do When You're Just Out Running Around

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

Almost all of us have days when we have a track workout scheduled - but we just don't want to go. It may be that we have been to the track a little too often recently, and that the thought of running ovals gives us a distinct feeling of ennui or dread. Or it might be that even though we are highly motivated there is simply no sense in attempting our pace-based effort on the track, since wind or rain would make it impossible to maintain a planned velocity. In such cases, is there an alternative workout which would provide benefits similar to the projected track session? If we decided to run somewhere else, in a place at which we really enjoy running, could we give big boosts to vVO2max, lactate threshold, economy, and speed - the kind of booster shots that the track running would have furnished, even if we don't actually run at a specific pace?

Thanks to recent research carried out by Stephen Seiler and Jarl Espen Sjursen from the Department of Health and Sport at Agder University College in Kristiansand, Norway, we know that the answer to these questions is a resounding "yes." In the Seiler-Sjursen investigation, runners were able to conduct great interval workouts even when they did not attempt to run at specific paces (1).

12 athletes (nine males and three females) from a Kristiansand running club participated in the study; all trained regularly, competed in races, and carried out interval training routinely. The runners had been training for at least four years prior to the onset of the investigation and averaged 5.4 workouts per week, with two weekly interval sessions.

During the four consecutive weeks following this initial testing, each athlete performed a "self-paced" interval workout on a laboratory treadmill once a week as a replacement for one of his/her usual interval sessions. No running velocity was specified for these lab-treadmill sessions; each athlete was simply instructed to run as well as he could. Work-interval length was tightly controlled, however, and was set at one, two, four, or six minutes, depending on the workout. The work-to-rest ration was set at 1:1, so that recovery intervals were always equal in time duration to the work intervals, and the total amount of quality running carried out per workout was fixed at 24 minutes.

Thus, during one week the athletes would run 24 X 1 minute, with 1-minute recoveries; during another they would perform 12 X 2 minutes, with 2-minute recoveries. Within yet another week, the runners would hit 6 X 4 minutes (4-minute recoveries), and they would also complete a session with 4 X 6 minutes (6-minute recoveries). These workouts were performed in random order over the four-week period. As mentioned, the athletes attempted to maintain the highest average running velocity they could across the full set of work bouts within each interval session, although no specific velocity was called for. Just as the athletes selected their own intensity for each work interval, they were also free to choose their running pace during the recovery intervals. The study was carried out during the early pre-competition phase of training (from mid-February through early March), and the subjects were instructed to refrain from hard training on the day prior to the self-paced interval sessions.

As you might expect, several of the runners underestimated their sustainable velocity during the initial work intervals, apparently in an attempt to make sure there was "still something in the tank" for the last intervals of the workout. When the average running velocity of the first four minutes of quality running were compared with the mean velocity over the last four minutes of the sessions (minutes 21 through 24), the upward swing in actual velocity averaged 5 percent, 4 percent, 4 percent, and 1.5 percent for the one-, two-, four-, and six-minute work durations, respectively.

The goal of the research, of course, was to see whether the resulting workouts would be high-quality - and also to determine whether specific work-interval lengths would produce better workouts when athletes were free to choose their own intensity.

There was little question that the self-paced workouts were high-quality. All four sessions, for example, shot lactate levels up to nearly 5 mmol/Liter and crested heart rate at over 90 percent of maximum during the work intervals. There were, however, some very interesting differences between the sessions.

For example, the peak rate of oxygen consumption reached during the work intervals was highest for the two-, four-, and six-minute intervals, compared with one-minute surging; VO2peak reached 92 to 93 percent of VO2max with the former work-interval lengths, versus just 82 percent of VO2max for the one-minute work intervals. Six of the 12 runners reached their highest level of oxygen consumption during the four-minute-work-interval session. Perhaps surprisingly, however, average oxygen consumption for the entire workout was absolutely equivalent between the four sessions!

The reason for this was that oxygen consumption during recovery was significantly lower for the two-, four-, and six-minute workouts, compared with the one-minute affairs. Essentially, oxygen-consumption rate dipped to as low as 26 percent of VO2max during the two-, four-, and six-minute recoveries but slipped to only 46 percent of max with the one-minute recoveries. In effect, oxygen-consumption rate was lower during the work intervals for the one-minute-work-interval session, compared with the two-, four-, and six-minute intervals, but oxygen-consumption rate was greater during the recoveries for the one-minute-work-interval session, compared with two-, four-, and six-minute recoveries. This balanced out and left the one-minute intervals in the same average overall oxygen-consumption bag as the longer intervals.

Blood-lactate levels and ratings of perceived exertions were virtually identical for the four different workouts, but there were very interesting differences in running speed. Specifically, the athletes ran fastest of all when the work-interval lengths were set at one minute, a little slower when the interval durations were two minutes, slower still at four minutes, and slowest of all with the six-minute intervals.

Before we continue this discussion of speed, we should perhaps answer the question which just popped into your mind: If the athletes were running more slowly with the two-, four-, and six-minute intervals (compared with the one-minute blasts), how could peak oxygen-consumption rate be higher with those intervals, compared with the one-minute jobs? Are not running speed and oxygen-consumption rate correlated?

Indeed they are, but time plays a role here, too. That is, when you run at a specific pace, it takes awhile for oxygen-consumption rate to rise to the topmost level associated with that pace. One minute is not long enough for the rise to be completed, which is why one-minute intervals were associated with more modest mountain-tops of O2 consumption. Two minutes, on the other hand, usually do provide adequate time for oxygen intaking to reach its apex. Thus, as you can see, you could run very fast for one minute and yet never take in oxygen at as high a rate as the fellow/gal running more slowly - but for two, four, or six minutes at a time; the latter intervals allow more time for oxygen to "climb the ladder."

As mentioned, athletes ran fastest with the one-minute intervals, which is not so surprising. Runners are more likely to "give it all they've got" when they know that the torture will be over in one minute, compared with two, four, or six minutes of potential agony. There is definitely a tendency to explore higher speeds when a runner knows that top-end sizzling will only have to last for 60 seconds. As a result, the one-minute intervals were performed at an average speed of 113 percent of vVO2max, while the twos went down with 107 percent of vVO2max, the fours called up 105 percent, and the six-minute big boys got 102 percent of vVO2max.

Were all of the workouts high-quality? Absolutely! If you went to a park, the beach, or a forest trail and ran 24 X 1, 12 X 2, 6 X 4, or 4 X 6, while attempting to run as well as you could, would you get a great workout? Of course! Is one workout "better" than the others? This depends on what you are trying to accomplish.

If you want a workout which pushes your oxygen-utilization system to the edge, it would appear that the two-, four-, and six-minute work-interval lengths would be ideal (and perhaps especially the four-minute intervals, since they prodded half of the athletes to reach their utmost oxygen grabbing), compared with the one-minute saunterings. This would appear to be particularly true since the recovery intensities employed by the 12 athletes in this Norwegian study were extraordinarily light - settling at just 26 to 31 percent of VO2max during the two-, four-, and six-minute workouts. Ordinarily, a reasonable athlete can maintain at least 50 percent of VO2max during a recovery period, and if that had been the case in this study the waves of oxygen consumption for the two-, four-, and six-minute-interval workouts might have been even higher (the one-minute intervallers did manage to get O2 consumption up to a typical 46 percent of VO2max during their recoveries). In addition, it is important to note that rambling continuously in a quality way for four to six minutes at a time is more like a race situation, compared to a one-minute, on-off pattern. Thus, the longer intervals are more specific to racing, too.

However, also note that the one-minute intervals do offer a key advantage - the opportunity to run faster. Running more quickly during workouts will have a superior effect on maximal running velocity, which is a good predictor of performance in events ranging from 800 meters all the way up to the half-marathon. Running more speedily should also have a better impact on running economy at high speed and thus might provide more of a nudge for vVO2max, compared with the longer-interval workouts, even though the latter seem to feature higher peak oxygen-consumption rates.

Of course, there is nothing at all to stop you from mixing the different kinds of intervals within your self-paced workouts. For example, you might roll through 12 X 1 minutes, very fast, while you are feeling pretty fresh, and then settle down for 3 X 4 minutes, not quite so fast but still pushing it. This would really mimic a race situation, in which you must sustain a challenging pace on a more-continuous basis, even though you are experiencing a lot of fatigue. You could get creative, too, having fun with a workout consisting of 4 X 1, then 3 X 2, then 2 X 4, and then finally 1 X 6 in sequence, with equal recoveries throughout.

The Kristiansand research revealed some interesting things about the heart-rate response to interval training. For example, the peak heart rate reached during each work interval inched up over the course of a workout, usually edging up by about five beats per minute from the first work interval to the last. What was much more significant, however, was the upward trend in end-recovery heart rate (the heart rate observed at the end of each recovery period) over the course of the sessions. In fact, end-recovery heart rate was often 25 beats per minute higher at the end of the recovery period which was just prior to the last work interval of a session, compared with the first recovery period of a workout. This was true even though recovery oxygen-consumption rate and even blood-lactate level remained stable over the course of the sessions. In effect, recovery heart rate did not seem to be tightly connected to recovery processes at the muscular level, and thus the practice of using heart-rate recovery as a guide as to when to begin a subsequent work interval would appear to have a shaky foundation. Yet, we still have coaches who advocate beginning work intervals when heart rate reaches 120 (or some other magical figure) during recovery.

So, what should you do if you can't - or won't - go to the track on a certain day? Simply have fun! Warm up thoroughly, and then - in a place where you really enjoy running - perform a self-paced workout, selecting the work-interval lengths according to your preference and goals. You may not be able to finish 24 minutes of quality running during your first self-paced stab, depending on your fitness and experience; if not, you can gradually work up to this amount of quality running per session (and slightly more, if your fitness warrants). If you want to work on speed, skew things toward the one-minute intervals; if you want to stress oxygen consumption and 5- or 10-K-type paces, bias the workout toward four- and six-minute intervals. A key thing to remember is that you will have a great workout - no matter what work-interval duration you select. You can simply have fun with the session, relaxing yet pushing yourself to run quickly - and without any specific worries about the actual pace you are maintaining. The result will certainly be higher fitness; in this Norwegian study, the athletes increased the total distance they could run at a hard pace until exhaustion was reached by a full 5 percent, simply by replacing four of their typical interval workouts with the self-paced interval sessions. ©

Reference

(1) "Effect of Work Duration on Physiological and Rating Scale of Perceived Exertion Responses during Self-Paced Interval Training," Scandinavian Journal of Medicine and Science in Sports, Vol. 14, pp. 1-8, 2004

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