Endurance training: both anaerobic and aerobic training is vital for optimal endurance performance

Conventional training for distance events is dead: now you need to work on your anaerobic power

If you had 100 endurance runners in front of you and you wanted to figure out which ones would finish near the front in a 5k race, how could you do it? In fact, one of the simplest and most effective forecasting techniques is to time each runner in a 20m dash. The runners with the fastest 20m times would also be fastest in the 5k.

While this linkage seems illogical, since the sprint is an 'anaerobic' event and the 5k is a test of 'aerobic' mettle, the 20m test is very accurate. It has been verified in research carried out by Heikki Rusko and colleagues at the KIHU Research Institute for Olympic Sports in Jyvaskyla, Finland in a study of 17 male endurance runners with roughly similar 5k clockings (1). The connection between 20m and 5k speeds was strong, even though the average 20m speed of 8.15m per second was roughly 76% faster than 5k speed. In fact, 20m time was a better predictor of 5k speed than that much-vaunted 'aerobic' variable VO2max and almost as good as running economy.

Could the connection be purely coincidental? If you are inclined to think so, consider some brand new research from the University of Nebraska, in which Kris Berg and his colleagues determined that 10k performance times can be predicted with a high degree of accuracy using two additional 'anaerobic' characteristics - 300m sprint time and plyometric leaping distance. In addition, they found significant correlations between 10k performance and 50m sprint time as well as vertical jumping ability(2). Why should 'anaerobic' physiological attributes be so closely linked with success in purely 'aerobic' events?

To understand what is really going on, let's take a close look at the Nebraska study. In this fascinating piece of work, the researchers examined 36 trained runners (20 men and 16 women) whose 10k times varied from 32:36 to 56:24. The subjects, aged 19 to 35, were running about 30 miles per week and had trained five times weekly for at least six months before the study started. Nineteen of them engaged in some form of strength training and 27 were preparing for a marathon while the research was carried out

Berg and his fellow researchers were wise to put all of the runners through a 50m sprint test: for essentially none of the power required for this event is derived aerobically. The energy for 50m sprinting comes from the 'phosphagen system' within muscle cells (ie from existing ATP and from the high-energy phosphates which are donated by creatine phosphate to ADP to make ATP). Not even a molecule of oxygen is required for this process, and thus the 50m sprint is a nice 'anaerobic' test.

The 300m run was another good choice: running all-out for 300m from a standing start puts little energetic demand on the aerobic system; instead it depletes the phosphagen system in about 10 seconds-or-so and then relies almost exclusively on the 'glycolytic energy system', an oxygen-independent system which relies on the breakdown of glucose to pyruvate and lactate for the creation of usable energy.

The athletes in the study also performed two vertical-jump tests, one from a standing position with a countermovement, and the other from a static, flexed-knee position. For these tests, each athlete's reach was assessed as he/she stood motionless next to a Vertec instrument, reaching as far as possible with their dominant arms, without letting their heels rise off the floor. To determine actual jumping height, the highest reach in inches from this standing position was subtracted from the highest mark made on the Vertec instrument during a specific type of jump.

For the jump with countermovement, the athletes started in a standing position next to the Vertec, quickly descended into a semi-crouched, flexed-knee position, then immediately jumped straight up as powerfully as possible, attempting to touch the highest possible point on the Vertec device. For the no-countermovement vertical jump, the athletes started from a static take-off position, with the knees locked at 90deg. of flexion. Each athlete held this position for three seconds and then jumped straight upwards as high as possible.

Energy-cheap elastic reactions
The difference between the heights of the countermovement and no-countermovement jumps is a measure of the elastic properties of muscle. In the countermovement jump, the 'snap-back' of muscles which have been quickly stretched provides a significant amount of the force required for vertical leaping without the penalty of direct energy cost; for the no-countermovement jumps, the force is provided primarily by energy-costly active contractions of propulsive muscles which are forced to work 'from a standing start'. As you might expect, athletes whose muscles can generate much work by means of energy-cheap elastic reactions tend to be able to run (or cycle, swim, row, or ski) quite efficiently, ie at a relatively low percentage of their maximal rate of energy usage. Such athletes tend to find specific speeds of movement easier to sustain than those athletes whose muscles have less highly-developed elastic properties.

The final test of anaerobic prowess - the plyometric leap test - was initiated from a standing position from which the athletes performed three consecutive leaps by springing from one foot to the other, landing on both feet for the last one. In effect, the plyometric leap test is just like the triple jump performed in track and field, except that it is performed from a standing rather than running start. Actual plyometric leap length was measured from the starting line to heel which was closest to the starting line after the third leap.

Note that all of these tests can be carried out easily in the field, and all involve closed-kinetic-chain movements rather than open-chain movements. Four of the five anaerobic tests (50m sprint, the two types of vertical jump, and plyometric leaping) were carried out in random order on the same day; but because the 300m sprint induced greater fatigue than the other tests, it was carried out last. The tests were preceded by a 10-minute warm-up jog and stretching exercises.

As it turned out, although there were significant correlations between 10k time and 50m sprint time, countermovement jump height, non-countermovement jump height, and percentage body fat, the two best predictors of 10k success were plyometric leap distance and 300m sprint performance. In fact, plyometric leap distance on its own accounted for a whopping 74% of the variation in 10k race times for the entire 36-subject pool! Factoring in the 300m sprint helped a little, but not much - expanding the explained variance up to 78%.

To put it another way, one 'anaerobic' attribute - plyometric leap distance - was able to account for about three quarters of the variation in performance times for this relatively large group of 10k runners. So-called 'aerobic' variables such as VO2max, lactate threshold and running economy have been known to have a lesser impact on aerobic performance in various studies! Two 'anaerobic' attributes taken together - plyometric leap length plus 300m run time - accounted for almost four-fifths of the variation in 10k performance, which is also better than two combined classic aerobic variables have done in some investigations.

There are fundamental reasons for this linkage, which we will explain in a moment, and several other research studies also link the two apparent 'opposites'. For example, in Heikki Rusko's study, where 5k success was predicted by 20m time, it was also forecast by another high-speed attribute which Rusko called VMART - the maximal speed a runner could attain during a series of progressively more difficult, increasingly anaerobic sprints. During Rusko's strenuous VMART tests, the runners initially cruised for 20secs at a pace of 3.71m per second (7:14 per mile) on a treadmill with a gradient of four degrees; after 100s of recovery, they then burst along for 20secs at 4.06mps (6:36 per mile).

This pattern of 20secs bursts alternating with 100s recoveries continued to exhaustion, with each successive 20secs burst conducted at a speed which was 0.35mps faster than the previous interval. Mean speed at the point of collapse was 6.57mps (4:05 per mile), so the Finnish harriers did quite well. Naturally, though, their speeds were less than those attained during the 20m races (where 8.15mps was the mean velocity), which took place on flat ground with 'fresh legs' over a shorter distance.

As mentioned, the final speed attained during the VMART exertion was a great predictor of 5k prowess; in fact, like 20m race time, it was better than VO2max and - unlike 20m time - even better than running economy at foretelling 5k success.

The findings of Rusko and Berg are in accordance with those of the great Tim Noakes, who may have started the whole ball rolling with an elegant study published in 1988. In Noakes' investigation, endurance performance was well predicted by the top speed athletes could attain on a treadmill; those with the highest peak running speeds also had the best endurance race times (3). As with Rusko's research, peak running velocity was a better predictor of performance than VO2max and far superior to running economy.

If that were not enough, completely separate research has also found 50m sprint time to be well correlated with 10k performance(4). In addition, Ronald Bulbulian and colleagues found that 58% of the variation in five-mile run time in well-trained college athletes was accounted for by anaerobic work capacity(5).

Learn to extend your TTE
In yet another study, the famed exercise physiologist Dave Costill and his associate Joe Houmard took a close look at the physiological attributes of 10 runners who trained about 50 miles per week and averaged a time of 16:43 for the 5k(6). Although oxygen-dependent chemical reactions provide about 93% of the energy needed to run a 5k, maximal aerobic capacity (VO2max) turned out to be a poor predictor of performance in this group of good runners. The two best predictors of 5k finishing time were 'anaerobic power' and a variable known as 'time to exhaustion' (TTE).

The athletes' anaerobic power was measured during short sprints and vertical jumps. TTE was calculated as follows: a stopwatch started as each athlete began running on a flat treadmill at an intensity of 85% of VO2max, which occurs at about 92% of max heart rate; the treadmill grade was then increased by 3% every two minutes, and the clock stopped when the runner could no longer continue. TTE was simply the total time an athlete could last on the treadmill and represented the ability to sustain very high-intensity, significantly anaerobic running. Thus, this study agreed with the others mentioned thus far in finding that anaerobic factors outweighed aerobic variables in determining overall endurance (aka aerobic) performance.
The fundamental mechanisms underlying the connection between outstanding anaerobic attributes and exceptional endurance performances are not hard to grasp. For example, just as individuals with very high maximal aerobic capacities tend to beat those with lower capacities, so endurance runners with high maximal running speeds will tend to outclass those with lower speeds. If endurance runner A has a peak running velocity of 8mps, while runner B has a max of 6.8mps, who do you think has a better chance of running a 5k in 15 minutes flat (at 5.56mps) For runner A, 15-flat pace would be 70% of max speed; for B, it would be 82%.

To put some more numbers on this kind of thinking, if you have a max speed of 8.15mps, a 5k speed of 4.63mps (for an 18-minute finishing time) would represent only 57% of running-speed max; on the other hand, if you are a poor soul with a maximum of just 7mps, you would have to settle in at 66% of your max during an 18-minute 5k, and the pace would feel quite a bit tougher. Having a high max velocity makes it more feasible - and likely - that you will be able to handle the higher end of possible race speeds in the 5k, 10k, half-marathon and marathon as well. Basically, you've already got the ability to run fast, and your key chore is to train in a manner that maximally extends the time over which you can sustain that fast running.

Other 'anaerobic' attributes besides peak speed should also have a strong impact on endurance performance. Think about Rusko's VMART tests, for example, in which 20secs work intervals were carried out on a treadmill with a 4deg. gradient, with speed progressing from 7:13 to 3:43 (for some athletes). The best VMART runners would have to be superb not just at running fast but also at minimising leg muscle fatigue during high-intensity exercise. This capacity would depend on good 'buffering' within muscle cells (the ability to deal with increases in muscle acidity associated with very fast running) and an excellent lactate-clearance capacity. These attributes would give runners not just high anaerobic capacities but also great success in demanding aerobic events.

On the basis of his laboratory investigations, Tim Noakes believed that something called 'muscle contractility' - a measure of the speed and force of muscle contractions - was very important for endurance success. He pointed out that athletes with excellent muscle contractility can achieve very high workloads and thus very high rates of oxygen consumption during intense workouts. If they can work at higher relative percentages of VO2max and vVO2max, they should be able to produce greater adaptations in those key variables than those who work at lower percentages. In other words, an 'anaerobic attribute' - muscle contractility or power - can lead to greater-than-usual aerobic adaptations. Incidentally, outstanding contractility might also position an athlete to carry out more work at a high fraction of max running velocity, which would, of course, be an excellent way to optimise that crucial performance variable. Note, too, that exceptional contractility would also expand plyometric leaping distance, the variable which Berg et al found to be so highly predictive of 10k performance.

Fast footstrikers are fast runners
Taking a slightly different approach, Heikki Rusko argued that 'neuromuscular characteristics' were a key component of endurance success; by this, he meant that runners whose muscles were capable of fast force production, with rapid, well-coordinated explosive contractions (as evidenced by high VMART speeds and excellent 20m times) would have a definite edge in distance events. He supported this theory by showing that 5k velocity was inversely related to footstrike time, both in the 20m dash and the 5k itself. In both events, if you could sort runners by their footstrike times, with the fastest footstrikers on one end and the slowest at the other, you would also have done a nice job of sorting them according to their race times. The best 5k runners were not just the ones with the best VO2max and economy - in fact, those variables had fairly weak predictive power. The top-class competitors were those with powerful neuromuscular characteristics, as evidenced by their explosive footstrikes.

Let's take a moment to put some numbers on this: a reduction in footstrike time of just 1/300 of a second could reduce 5k time by 10 seconds for a 16-minute 5k runner (providing it didn't lead to a loss of stride length), while trimming contact time by 1/100 of a second could lead to a 30-second improvement. Interestingly, the difference in average contact time between the fastest and slowest 5k runners in Rusko's study was about 27 milliseconds (2.7 hundredths of a second), and this difference was associated with a 54-second difference in finishing time.

Rusko was also able to show that stride rate was directly related to 5k speed: the higher the stride rate, the faster the finish time. Since stride lengths were comparable for the runners in his study, it was clearly the decrease in footstrike time which increased stride rate; since this occurred without a drop in stride length, the more-abridged footstrike pattern allowed runners to eat up more road during each minute of running.

As a sportsperson who runs, you should be aware that the so-called 'anaerobic charcteristics' which have a strong impact on distance running performance - plyometric leap distance, 20m, 50m and 300m sprint times, footstrike time, stride rate, muscle contractility, neuromuscular characteristics, VMART, muscle buffering capacity and max running speed - are all very trainable, and you need to emphasise them in your training if you want to reach your peak level of performance. To improve those characteristics, you will need a training programme which emphasises high-intensity running and which includes a strengthening plan to cycle you through proprioceptive training, general, running-specific and explosive strength training.

The underlying aim of this strengthening programme is to optimise your coordination, so that little muscular force production is needed to stabilise awkward movements and max-possible muscular force is instead channelled into propulsion. Proprioceptive training kick-starts this process, and the general strengthening work which follows continues the progression, while helping to make the whole body resistant to fatigue during running. Running-specific strength training and subsequent hill training finish the process of boosting propulsive force production by your leg muscles, and the explosive training which follows allows all that force to be created more quickly, heightening your power. As you do this, of course, you will also be progressively increasing the intensity of your 'pure running' training, carrying out more work at above-lactate-threshold speed and at vVO2max and beyond.

Conventional training for distance events is dead! It's no longer enough to run miles and focus only on your aerobic development. In fact, it never was enough - we just lacked the scientific information to prove it. Then once we began to see that anaerobic characteristics might be helpful to distance runners, we did not at first understand why this apparent paradox was nothing of the sort.

The really good news is that power (anaerobic) factors can be improved by even the most plodding of runners, and this is not a risky process even for the inexperienced. If you train to improve your power in a progressive and reasonable way, the process will prevent injuries rather than cause them. And eventually your anaerobic and aerobic characteristics should fuse to produce your best-possible race times - from 50 metres all the way up to the marathon.

Owen Anderson

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