On one level youd think we would have pieced it together a long time ago, tells Peter Weyand, one of the worlds resulting students of running and prof of applied physiology and biomechanics at the South Methodist University in Dallas, Texas. Newton figured out the laws of motion centuries ago but when we when we apply them to the human body it gets really complex, really quickly.
Simply analysing the extreme motion and exertions of a sprinter is challenging. Weyand and his squad have a large treadmill in their lab capable of rolling at 90 mph. In the penalise max exam, athletes straddle the moving belt and hop on for a few seconds at a time. They start slacken, with rests in between. We increase the speed until the athlete cant maintain it, the prof tells. We require eight steps without moving backwards for a good trial.
The tests are a safer version of jumping off the back of an old Routemaster bus and remaining upright for eight paces athletes wear harness in case they trip but how fast is the bus running? The unofficial record on our treadmill is 11.72 metres per second, Weyand tells. Thats 26.7 mph, or not far off a city speed limit, or Bolts peak speed during his 2009 world record running of 27.8 mph. When we have elite athletes do the test, the whole office comes over to watch.
High-speed treadmills, slow-motion imaging and pressure sensors have allowed scientists to study aspects of upper-clas sprinting that were largely unknown as recently as 15 years ago. If you asked a coach in the late 1990 s what they were doing it was all very much based on form, Weyand says. But when we started this work back at that time, the first thing we figured out is that what stimulates these guys fast is how forcefully they can reached the ground in relation to their body weight.
When Usain Bolt looks like hes floating over the way, hes truly not. That extreme gurgle in the face that slow motion footage reveals in some athletes demonstrates the forces that transfer from foot to floor. We know that Bolt will peak out with each step at about five times his weight, while non-sprinting athletes will peak at about 3.5 hours, Weyand explains. The science is clear: the top athletes are specialised to deliver the most force to the ground and thats what attains them fast. But even now I think were still in the formative stage it hasnt yet translated into broad practises in training.
The key, though, is to gain force without body weight, while not sacrificing the brute strength required to accelerate out of the blocks. Weyand likens the steps a top sprinter takes to the punches of a boxer vastly powerful but also lightning fast. The truly remarkable thing is that sprint athletes not only reach a peak of four or five times body weight with each step but that they do so in an incredibly short period of time, he says. A world-class sprinters foot expends less than a tenth of a second on the floor, three times faster than the average blink of an eye.
To generate such forces and turn steps into accuracy punches, elite sprinting has become largely removed from the instinctive sports-day dash of our youth. Its actually a reasonably unnatural action, tells
Craig Pickering, a British former sprinter who won bronze in the 100 -metre relay team at the 2007 World Championships. As soon as the foot makes the floor you pick it up again in front of the body as quick as you can for the next step. Nothing happens behind the body.
Dr Ralph Mann, a veteran American sprinter turned biomechanist, has done much of the work to refine the optimal technique. He measures a athlete to generate a stick figure in his or her image. Use vast pools of data from the hundreds of top sprinters he has worked with, a computer program gives the stick sprinter ideal mechanics for every step of a sprint. On the way, the stick person can be set to a personal-best or even world-record pace and laid over slow-motion footage of the athlete to compare movements. Going faster becomes, in part, training exercises in mirroring your own stick figure, and repeating every minute adjustment of foot position or knee lift so that it becomes wired in the brain.
The brain is the unseen muscle behind all great athletes, and in the 100 -metre sprint it has to work on autopilot. We learn motion in the motor cortex but when its locked in it moves to the back of the brain, says
Aki Salo, an associate professor in sport biomechanics at the University of Bath. Salo works with a number of British athletes and has studied the performance of Ashleigh Nelson, a sprinter who travelled to Rio as part of the 100-metre relay team, for our movie. If Ashleigh starts to think about other athletes or where she is in the race, the neural system starts to give way and technique breaks down.
After a good race you probably remember nothing, Pickering adds. I merely have memories of bad races.
If sprinting is a battle to focus, its also a fight against wearines, which sets in nearly instantaneously. Weyand says another area of survey still being explored is the mechanics and chemistry of tiring. Sprinters who win by appearing to blizzard ahead in the final metres are not speeding up, but slowing down the least speedily. Bolt makes top speed about 70 m into the race. Tests done on stationary bikes, in which big resistance is added suddenly to a rider turning the pedals at a high cadence, show that the power exerted fells on the second stroke and continues to decline.
Its the same on the way, Weyand tells. When Bolt hits top speed second hes already fatigued. What we can do is quantify the rate of that fatigue and calculate the loss in performance. One of Bolts biggest advantages is that his long legs mean that he runs 41 steps in a race compared with 45 for his contenders; his muscles have four fewer chances to get tired. Each time, the muscles use a chemical energy called ATP, which has to be replenished constantly to maintain performance. We think theres something about that cycle that causes tirednes but dont know exactly what it is yet, he adds. One place scientists are looking for the answer is the heart, which contracts in the same route but never get tired.
The most common topic specialists in this field are asked is, you guessed it, how fast can a human operate 100 metres? I think we can go substantially faster, Weyand says. But how fast is a question that science isnt very good at answering. One Australian physiologist calculated in 2014 that a sprinter with Bolts force could preserve it while also cutting contact hour with the ground to only 70 milliseconds( down from 80 or so ). This would result in a top speed of 12. 75 meters per second, or 28.53 mph and a new world record of 9.27 seconds.
But theres always the possibility that some outlier will come along and break apart the record book, Weyand tells. He mentions
Eero Mntyranta, the champ Finnish cross-country skier who had a genetic defect that entailed his red blood cell could carry more oxygen. He was, in effect, a natural doper. There are multiple ways to break new barriers, whether its better knowledge and training or technique, or the unexpected, he adds. What we do know is that in the modern era the incentives to go faster are huge.