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Here's how: If you use running in your sport - whether it be football, basketball, tennis or even running itself - one of your key training goals should be to reduce the energy cost of your running. If you do so, any given speed will represent a lower fraction of your maximal cost of movement, and thus will be easier for you to establish and sustain. To understand the fundamentals of cost-cutting while running, we should first take a look at the research of the late, great, Professor Dick Taylor of Harvard University. Taylor and his colleagues worked with a variety of different animals, training them to run on treadmill belts while wearing oxygen-collecting masks. By calculating how much oxygen the animals were using in the course of this activity, Taylor and co could determine their energy cost. As a general rule, as long as an animal is not moving too quickly, each cubic centimetre of oxygen it consumes is associated with the production of about 20 joules of energy; Calculating animals' oxygen usage during exercise is actually a simple matter. Just two pieces of information are really required: the amount of air expired into the mask or hood, and the oxygen content of the expired air. Thus, the animal would be expending 120 x 20 = 2400 joules of energy per minute. Although Taylor worked with a variety of animals, some of his best work was carried out on the treadmill with small ponies. These creatures are especially interesting because they can employ three quite different gaits, walking when they are moving slowly, trotting at medium speeds, and break into a gallop when they want to move very quickly. Each of these styles of movement has a unique footfall pattern, and Taylor and his student, Dan Hoyt, were able to determine the energy costs (in joules per minute) associated with each . One of the most surprising things about the Taylor-Hoyt findings was that the metabolic cost of movement at a specific speed was entirely dependent on the chosen gait. For example, at a pace of around 35m per second (7:40 per mile), trotting cost almost 25% less than galloping. We'll come on to how these findings can improve your running in a moment. Before we do that, though, it's important to note that when Taylor and Hoyt plotted energy cost as a function of speed (with speed on the x-axis), each gait (walking, trotting, or running) produced a U-shaped' graph (a horseshoe pattern with a low point and two curving arms rising on either side of it). In other words, each gait had a speed associated with a minimum energy cost per metre; moving faster than that speed raised the cost of movement, but so did moving slower. For each gait style, there was one speed which was most economical. This may help to explain why some athletes have trouble slowing down during their running workouts. They may have a particular running speed which is most efficient in that it is associated with a low energy and oxygen cost along with a modest heart rate. Attempting to run slower than this high-efficiency pace may paradoxically raise the energy cost and feel tougher! The natural tendency in such cases would be for the athlete to speed up in order to feel more comfortable during the workout; but such accelerations could, in turn, raise the risk of overtraining (remembering that the impact forces experienced by the legs increase as a function of running speed). Spontaneous selection of gaits The phenomenon of slow paces feeling difficult might be particularly applicable to athletes with a relatively high percentage of fast-twitch fibres in their leg muscles; if they routinely train at fast speeds, making primary use of their fast-twitchers, slowing down might cause the fast-twitch fibres to take a break, leaving the athlete to rely on the less-used and therefore less-efficient slow-twitch cells. Returning to the ponies, their most efficient walking speed was about 125m per second, while their most economical speeds for trotting and galloping were just above 3m per second and just above 6m per second respectively. When Taylor and Hoyt filmed the ponies as they moved freely and spontaneously around the paddock, they found that the creatures spontaneously selected almost precisely those speeds for each of the three gaits. Were the ponies most efficient at certain walking, trotting, and galloping speeds because those were the speeds they repeatedly practised, or were they somehow gravitating toward the locked-in' paces which were naturally most economical for them, given their innate physiology and anatomy? We simply don't know, but it is clear that humans tend to become most efficient at the speeds they most frequently practise. That is one reason why marathon runners often have great difficulty sustaining their goal pace for the full duration of a race: during their long training runs, they usually employ a speed which is slower than hoped-for race pace and thus build up considerable efficiency at this training pace. The efficiency at goal race speed, however, may remain untouched by these slower-than-race-pace amblings, and thus race day will frequently contain some unwelcome surprises. While goal speed might be maintained for 15 miles or so, the runner, when tired, will naturally gravitate toward the slower, more efficient speed with which he is so familiar. Regardless of whether or not practice made perfect for the ponies, it was certainly good policy for them to move at their lowest-cost velocities, as R McNeill Alexander, of Leeds University, has pointed out . Such movements save energy and allow more resources to be funnelled into useful activities like recovery, growth, immune-system function, and so on. For athletes, it makes paramount sense to spend as much time as possible during training at competition-specific speeds in order to optimise efficiency in competitive situations. However, there is another extremely interesting aspect to this story: since walking, trotting and galloping produce U-shaped curves, with the minimum cost of trotting occurring at a higher speed than walking and galloping a higher speed than trotting, the right arm of the U' for walking tends to cross over the left arm of the U' for trotting and ditto for trotting and galloping. Animals who want to go somewhere should avoid these crossover-point speeds, since they represent inefficient movement for each specific gait and may be associated with indecision about how to move. In Alexander's brilliant analysis (p66), he points out that if a pony decided to go from point A to point B at about 17m per second, that would be a costly mistake because this is a crossover point between the cost of walking and running, with either gait strategy producing a rather expansive expenditure of 400 joules per metre. The pony could choose to walk or trot, but either pattern would increase metabolic cost. A far better strategy for the little horse would be to trot the distance at 32m per second, slowing down to walk at about 12m per second when tired. With this strategy, he would cover the distance in a faster time: even if he divided the gait patterns equally, the average speed of 22m per second would still be greater than the crossover speed of 17 He would also be performing at lower cost since trotting at 32m per second and walking at 12m per second each cost just 300 joules per metre! Is it possible that US sports writer Jeff Galloway is right? For years, Galloway has been recommending the strategy of alternating between running and walking during marathons, arguing that this can reduce fatigue, enhance endurance, and even improve finishing time. Could it be that Galloway's proteges are using their most-efficient running speeds and most-economical walking paces and thereby reducing the cost of running the race, much like our ponies? If they slowed down their running pace and attempted to cover the whole distance by running, would they augment energy costs and glycogen depletion and finish in slower times? As it turns out, the cost crossover point in humans for walking and running occurs at about 2m per second (13:24 per mile). In other words, if you range above 2m per second, running is far more efficient t...
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