Instead, muscular forces stretch elastic tissues, such as tendons, and stored energy is subsequently recaptured at much faster rates when they recoil.
However, we know little about the effect of changing tendon properties. We do know that sprint runners have stiffer Achilles tendons than non-runners.
This should allow them to cope better with forces of over kg placed on the tendon and to recoil faster while under load during the propulsion phase of the foot-contact phase. We also know that exercise such as strength training tends to increase their stiffness while detraining reduces it. Another issue is that increased muscle mass increases limb inertia in much the same way as greater limb lengths do , so reducing the acceleration for a given joint torque production.
The best sprinters therefore have very low limb masses, which enables them to cyclically move their arms and legs at high speeds. Weyand likens the steps a top sprinter takes to the punches of a boxer — immensely powerful but also lightning fast.
To generate such forces and turn steps into precision punches, elite sprinting has become largely removed from the instinctive sports-day dash of our youth.
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 runner to generate a stick figure in his or her image.
Using 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 stride of a sprint.
On the track, the stick person can be set to a personal-best or even world-record pace and laid over slow-motion footage of the runner to compare movements. Going faster becomes, in part, an exercise 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 metre sprint it has to work on autopilot. 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 metre relay team , for our film.
Taller, more linear individuals are emerging as the better sprinters and we think it's got something to do with increased stride length," Dr Nevill said. Sprinters with longer legs have longer strides — an advantage in the middle stages of the race when they have reached their top speed, which they must maintain until the finish line.
Shorter, more powerful legs are better in the earlier, acceleration stage, but Bolt can evidently compensate for his slight disadvantage over his shorter, heavier competitors. Sprinting is an extreme form of running requiring a combination of physical and mental attributes that can be honed by intensive training. Yet most experts would agree that a world-class sprinter is born rather than made.
In Bolt's case, it helps that he is from Jamaica. Studies have shown that black athletes with West African ancestry have significantly more "fast-twitch" muscle fibres, which tire easily but contract more quickly than the "slow-twitch" fibres commonly found in long-distance runners. For example, large athletes are commonly found in the throwing events. The ability to accelerate an external object is proportional to height squared.
In general, the heaviest weightlifters lift the most weight and this is simply because they have so much mass, and consequently strength, that they can effectively overcome the inertia the tendency of a body to stay at rest of the load.
This is why we see so many small but powerful and mobile gymnasts. In other sports though, it is not that simple. Being tall facilitates a higher reach height at take off and this is a distinct advantage for the pole-vaulter.
When it comes to heat dissipation, small stature individuals tend to be better at off loading heat due to the smaller body surface area. This is actually an advantage in endurance events where the cardiac output is preserved as heat is unloaded easier.
In contrast there is better heat conservation in large individuals. This is obviously an advantage in activities where cold is a problem. We have already highlighted the key structural differences in terms of muscle fibre type between the endurance athlete and the sprinter. As you will recall, the sprinter is the one endowed with a dominance of the fast-twitch fibre. The accompanying table compares some of the key physiological differences between slow and fast twitch fibres.
Understanding these differences, believe it or not, does help us in choosing and designing training for the sprint and endurance athlete. Table 1 identifies some key functional characteristics that are indeed giving the sprinter an advantage in terms of speed. The speed of contraction is greater in the fast twitch muscle, the relaxation time is faster as well and the capacity to generate force is also higher than in the endurance fibre profile.
We can test the athlete to determine if he or she has a predominant fast or slow twitch profile. The Counter Movement Jump and the Squat Jump may be used to estimate the dominance of fibre type [3]. However, if you do not have access to such testing equipment, simply completing a wall reach vertical jump will tell you if you are lucky enough to be endowed with explosive qualities.
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