Running: the importance of race pacing

Race Pacing

The importance of quick starts in competitions: can kayakers convince you? Should you start each of your competitions in a blaze of speed and then attempt to ‘hold on’ during the latter stages of the contest? Would it not be better – less fatiguing and more efficient – to maintain an even, consistent pace throughout a race? Or is it best to start rather cautiously and go for a ‘negative split’ in your event, with the last half of the competition completed more quickly than the first?

Unfortunately, exercise scientists haven’t come up with definitive answers to these important questions. While numerous studies have examined the effects of different types of training on VO2max and lactate threshold, for example, investigations concerning the critically important topic of optimal race pacing have been few and far between. In fact, just four studies on race pacing were published in scientific journals between 1958 and 1967, after which pacing research went into an even deeper slump. Between 1967 and 1992 not a single pacing paper appeared in the peer-reviewed scientific literature. That wilderness period ended in 1993 with the publication of a paper by Carl Foster and his colleagues from the Sinai Samaritan Medical Center in Milwaukee, Wisconsin, which concluded that athletes competing in intense events lasting for three minutes-or-so should ‘negative-split’ their efforts to achieve the best-possible times (1).

According to Foster, who is now acknowledged as one of the world’s leading experts on pacing strategies, the negative-splitting should be in the form of ‘51-49’ racing – ie with the first half of the competition completed in 51% of the total time and the second half in just 49%. Not all exercise physiologists were happy with Foster’s conclusion, however; and nor were many coaches and athletes, a number of whom had tended to extol the merits of very quick starts. Indeed, Foster himself, in a subsequent study on élite speed skaters, demonstrated that an explosive start (and thus positive rather than negative-splitting) tended to produce the best times in 1,500m skating competitions lasting for about 110 seconds (2).

In this study, the faster a skater could start, the better his or her eventual race time would be. Critics carped that this phenomenon might be unique to speed skating, however, since any late-race fatigue which ensued as a result of an explosive beginning could be mitigated by the ability to glide along the ice in a relatively friction-free manner, with modest muscular expense. (Such gliding would not be possible for swimmers and runners, for example; and in terms of gliding potential, cyclists might lie somewhere between ice skaters and swimmers.) Nonetheless, Foster’s second investigation struck a resonant chord with savvy exercise physiologists.

Three race-pace strategies compared For one thing, the use of a fast-start strategy was supported by research investigating the effects of pacing strategies on computer-simulated 1,000m and 4,000m bicycle racing on the track(3). In the 1,000m simulations, which took approximately 60 seconds to complete, three strategies were evaluated:

  1. an all-out strategy, in which individuals started as fast as humanly possible and then ‘held on for dear life’ at the end;
  2. a fairly fast – but not all-out – start for the first 30 seconds, followed by solid, even pacing to the end;
  3. even pacing for the entire test.

As it turned out, the best result was produced by the all-out strategy. Things changed somewhat during the 4,000m simulation, however, suggesting that pacing strategy might well be a function of race distance. In this simulation, which took about 260 seconds to complete, three strategies were again compared:

  1. the all-out strategy, as above;
  2. a very fast – but not all-out – start for the first 12 seconds, followed by even pacing;
  3. even pacing throughout.

This time the best strategy was the fast start, followed by even pacing, not the maximal beginning. As with the 1,000m simulation, positive-splitting was preferable to even-paced efforts, but all-out beginnings were slightly disadvantageous. The researchers theorised that all-out starts might be optimal in competitions lasting 60 seconds or less, whereas fast starts and subsequent even pacing would be better for longer-lasting contests. The cycling simulations reinforced Foster’s second-study findings about rapid starts. But the findings were also appealing for another reason, which will emerge from the process I am about to describe.

How fast starts could make more fuel available to muscles

At rest, all muscle cells contain a high-energy chemical called phosphocreatine, which can act as a quick source of energy during the early stages of exercise. Specifically, phosphocreatine donates a phosphate group to a chemical called ADP in order to form ATP, which provides the actual energy needed for muscular contractions. All of this happens without the need to run through the time-consuming process of breaking down a molecule of fat or carbohydrate for energy, and it also occurs without the involvement of even a single molecule of oxygen. However, the concentration of the products which form as phosphocreatine splits in order to donate a phosphate group to ADP is directly proportional to the subsequent oxygen kinetics of the involved muscles(4).

Of course, greater rates of phosphocreatine breakdown occur as exercise intensity increases (since more fuel is required to support those higher intensities). Thus, the faster an athlete starts a race, the higher his/her oxygen-consumption rate should be after 30 seconds, 45 seconds, and so on. This increase in oxygen consumption as a result of fast starting could, in effect, make more fuel available to muscle cells, since the oxygen would be used in the breakdown of carbohydrate for energy. From this standpoint, quick starts would always be preferred in competitions, unless there were some side-effect of fast starting which could trump the oxygen effect.

One such side effect, of course, might be premature fatigue. As the intensity of exercise increases, oxygen consumption is stimulated to a greater extent, but there also tends to be a more significant disturbance of muscle acidity (pH). Muscle acidity increases (and intramuscular pH drops) as exercise intensity climbs, and this may actually inhibit energy production within muscles and interfere with the muscle contraction process(5).

Some researchers have even suggested that athletes ‘lose their form’ and move less efficiently as muscle acidity increases. If the fatigue of fast starting tended to overrule the oxygen advantage of getting out fast, then quick starts would not be generally valuable to athletes. To determine how oxygen kinetics really change in response to various starting strategies and to further evaluate the merits of various pacing techniques, scientists at the Department of Human Movement and Exercise Science at the University of Western Australia recently worked with eight highly-trained kayak paddlers(6).

The choice of kayakers for a pacing study was a particularly good one: after all, kayak events are contested at both Olympic and World Championship levels, and the margins of victory in such competitions are often exceedingly small. Thus, even diminutive benefits associated with particular pacing strategies could spell the difference between winning and losing or between a top-three placing (and the garnering of a medal) and being ‘out of the money’. The eight kayakers were 22 years old, weighed about 175 pounds and possessed a mean kayaking VO2max of 4.0 litres per minute (50 ml/kg-min). During the experimental trials, each kayaker performed – in random, counterbalanced order – four two-minute kayak ergometer tests, using two different strategies (even pace or all-out start). Before the two-minute tests, the subjects completed 15-minute warm-ups. How was the constant pace determined for the even-pace efforts? Before the study began, the kayakers completed two familiarisation trials with the two-minute test, using their normal pacing strategies and performing at their best-possible levels. The average power associated with each athlete’s best two-minute result was then used as the specific pace of the even-pace experimental trials, and athletes were required to accelerate up to this pace quickly at the beginning of the test. For the all-out strategy, athletes were asked to engage in absolute-maximum effort for the first 10 seconds, drop down to an even pace over the next five seconds and then do their best for the remainder of the two-minute exertion.

As you might expect, the even-pace kayakers fared better during the second minute of the two-minute test, working at an average intensity of 337 Watts, compared with just 323 Watts for the all-out starters (an increase in power of more than 4%). Super-fast starts have a way of extracting fatigue and pain ‘tolls’ during the latter stages of competitions, as you may have experienced for yourself. If the kayakers had been racing, they would have been moving faster during the second minute with the even-pace strategy. Despite this, however, the super-fast start proved far superior to the stodgy, even pacing. Average power during the first minute was about 12% higher with the all-out-start strategy (374 versus 335 Watts) and this was more than enough to offset the 4% lower power associated with maximal starting over the last half of the trial. In addition, peak power was far greater with the all-out start, capping at 748 Watts for the max starters during their first 10 seconds of kayaking, but cresting at just 558 Watts for the even pacers as they surged at the finish of the effort.

Although average power was significantly greater overall for the max-start kayakers, average power was greater for the even pacers during the fifth and sixth 15-second intervals of the tests. This disparity suggests that the negative effects of the max start (possibly including increased muscle acidity) began to appear after about 60 seconds and persisted through at least 90 seconds of the effort. Over the last 30 seconds of the test, however, the max starters were able to make a comeback and exert just as much power as the even pacers, perhaps in part because they knew the end was in sight. (Athletes handle fatigue and muscular distress more easily and are more willing to step up force production near the end of an exertion.)

Fatigue following max starts does not greatly impair performance

Overall, what is really remarkable about this study is that the max-start kayakers were able to maintain power outputs which were just as high as those sustained by the steady-pacers for five out of the seven 15-second intervals which followed the opening 15 seconds of the two-minute efforts. In the two intervals in which the max starters were ‘deficient’, the loss-of-power penalties were small. Any lingering fatigue remaining from the maximal start did not present a significant performance problem. What about the theory that max starts boost oxygen-consumption rates more than evenly-paced efforts? As it turned out, oxygen-consumption rates were higher for the max starters after both 30 and 45 seconds of the tests, indicating that the amazing start-offs did spur oxygen consumption. After one minute, however, oxygen consumption rates were the same for both groups; in fact, both groups reached VO2max after one minute and stayed at max aerobic capacity for the full second minute of the test. Since oxygen consumption rates were higher for the max kayakers after 30 and 45 seconds, their total oxygen consumption was greater, and this may offer an explanation for their exceptional ability to keep up with the even pacers, in spite of their explosive starts. The big early burst in oxygen consumption might have helped to control potential increases in muscle acidity in the maximal starters and thus kept fatigue from mounting to outrageous levels.

Overall, max starters consumed 7.3 litres of oxygen during their two-minute efforts, while even pacers settled for just 6.9l – about a 6% difference. This in itself is interesting, since most athletes and coaches would consider the max-start strategy to be more ‘anaerobic’ in nature than the even-pace technique. In fact, this 6% boost in oxygen consumption in the max starters can more than account for their 5% advantage in average power during the two-minute tests. It’s clear that the all-out starting strategy was superior to the even-pace technique in these very intense two-minute kayak exertions, in which VO2max was sustained for at least half of the total effort. All-out starters ‘stormed ahead’ of even pacers (in terms of power output) during the first 15 seconds of the tests and then lost very little of the ground (or should we say water) they had gained. As mentioned, one reason for the very good (and somewhat surprising) fatigue resistance in the max starters may have been their high early rates of oxygen consumption, which could prevent big increases in muscle acidity. There should be no ‘down’ side to this kind of oxygen gulping; although it meant that max starters were working at higher percentages of VO2max than even pacers for about 45 seconds during the tests, they were still below VO2max at this time and didn’t even ‘hit’ VO2max earlier (because from 45-60 seconds, oxygen usage increased at a slower rate for the max starters than the even-pacers). Putting together the results of these two studies, there is strong evidence that all-out – or at least very fast – starts are best for competitions lasting for about four minutes or less. Such beginnings kick-start oxygen consumption and allow athletes to put significant distance between themselves and competitors – distance which may never be completely made up. In a two-minute race, for example, it certainly makes sense to blast off for the first 15 seconds-or-so and then settle into a rhythm which can be held until it is time to attempt a final surge over the last 10 seconds.

Fast starts work best for short races

What about Foster’s original 51-49 investigation, which served up the quite-different conclusion that slightly slow starts worked better than max efforts. As it turns out, Foster’s fast starts were really not so fast after all, being determined as a percentage of the average 2k time-trial pace. These less-than-max starting intensities were then held constant for the first halves of the 2k trials – i.e. for about 100 seconds. By contrast, the fast starts employed in the cycling simulation and the kayak study were close-to-maximal efforts, lasting only 10-12 seconds. As a result, we may remain fairly content with our conclusion that short and extremely fast – rather than longer and moderately fast – beginnings represent ideal pacing for races lasting less than four minutes. For longer efforts (in competitions lasting from four to 60 minutes, for example), the picture is not so clear. Researchers have not really looked at the possible benefits of max starting during such exertions, partly in the belief that starting strategies become less important as race distance increases. Anecdotal evidence leans toward negative-splitting(7), which might imply lacklustre starting; but bear in mind that it is theoretically possible to negative-split a race and still have a very fast start; the quick beginning could be followed by a moderately-paced intermediate portion, leading into a rather furious closing rush to the finish, lasting longer than the fast beginning.

Runners tend to ‘crash and burn’ when they start long races very fast

A couple of other investigations do push the preference dial towards cool beginnings and overall negative splitting in longer competitions, though. Research carried out with runners, for example, suggests that they ‘crash and burn’ when they begin races or test trials at very rapid speeds, and perform better when they save furious accelerations for the second halves of their efforts(8). Such studies can be difficult to interpret, however, since the close-to-max beginnings may have been extended for over-long periods; if an athlete is going to start a race close-to-maximally, there must be some clear limit on how long that max effort will be sustained. Modest beginnings and negative splitting were also supported by the work of Jefferey Staab and Dr S F Siconolfi at the US Army Research Institute in Natick, Massachusetts (9). In this very ingenious study, 11 highly-trained runners participated in three 30-minute test races. One race took place on a perfectly level surface, but in the second the men ran uphill (on a 5% incline) between minutes six and 12 of the exertion, while in the third, they ran uphill (same inclination) between minutes 18 and 24.

The hills, of course, increased the intensity with which the athletes were working, so in effect the runners worked harder during the first half of test 2, when the hills came early, and during the second half of test 3, when the hills came late. In the event it turned out better to save the hard work for later, which is what athletes do when they negative-split. The runners were fastest on the level course, but they were faster on the late-hill course than on the early-hill toughie. Staab and Siconolfi concluded that the fatigue resulting from early, intense effort tended to put a damper on the ability to run fast throughout the remainder of a 30-minute run. If you are an athlete who competes in events lasting more than an hour, it’s clear that you should avoid fast starts completely. Studies carried out with marathon runners suggest that whenever they begin their races at paces more than 2% faster than their average for the marathon, they struggle mightily in the last six miles of the event(10). The theory is that fast starting uses up excessive quantities of muscle glycogen which, in turn, leads to late-race slowdowns.

The bottom line? If you are an athlete who competes in events lasting four minutes or less (and especially two minutes or less), you could experiment with close-to-maximal starts lasting 10-15 seconds; there is good evidence that this technique can produce your best performances. Of course, you should practise these starts frequently in training, so that your neuromuscular system can make the necessary adjustments and thus handle the explosive bursts more easily.

If you compete in events lasting from four to 60 minutes, there is no evidence that max starts are good for you, and the jury is still out on whether merely fast starts (not maximal but more intense than average pace for your race distance) are better than more conservative beginnings. For efforts lasting longer than 60 minutes, avoid maximal starts as avidly as you would a bout of Achilles tendinitis.

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