Every four years, we get to watch one of the greatest sporting events on the planet—and one of the shortest. The world stops as eight of the fastest sprinters on earth race to determine who is fastest in the 100-meter dash.
Usain Bolt dominated the last two Olympics, running 9.69 (Beijing 2008) and 9.63 (London 2012)—and this summer in Rio he again won Olympic gold in the 100-meter, running a 9.81 (slower than his fastest time of 9.48 in 2009).
What makes Usain Bolt the fastest man on Earth?
A paper by scientists Taylor & Beneke set out to model the characteristics of the three fastest sprinters on the planet—Bolt, Tyson Gay and Asafa Powell. The data they used was from the 2009 World Championships, where Bolt set his world record. The authors adopted the spring mass model to identify the characteristics that make these athletes so fast.
Estimated Spring Mass Model Characteristics Table
This table may not make any sense, but bear with me. All will be explained.
Here are the characteristics of Bolt that really stand out:
Body Mass and Height
From the data above, Bolt clearly has impressive body stats, dwarfing his competition. In a previous article, I discussed the physics of force production:
- force = mass x acceleration (F=ma)
Even before he lines up in the starting blocks, Bolt's greater body mass gives him a hefty advantage, allowing him to generate more force than his smaller competitors. The key is his ability to harness his additional mass, transferring it into greater force production without slowing his acceleration.
Centre of Mass Height - ΔYc (m)
Studies have shown that world record holders in the 100-meter sprint are becoming taller and heavier, and that height and weight are significants success factors [2, 3]. If height determines the center of mass, it is indicative of sprinting performance. The results of this study provide further evidence. Bolt has a greater maximal downward displacement of his center of mass during ground contact than either Gay or Powell.
Ground Contact Time - Tc (s)
The data from this study show that Bolt's running technique involves longer ground contact times—0.021 seconds and 0.011 seconds longer than Gay and Powell, respectively. This is contrary to the commonly held belief that shorter ground contact times produce larger vertical forces and faster runners.
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In scientific-speak, Bolt's longer ground contact time generates a larger impulse (Force x Time) and reduces his peak force loading, allowing him to generate greater speed and acceleration at lower force per unit of body weight.
Leg Stiffness - Kleg (kN.m-1)
The estimated leg stiffness of Bolt, Powell and Gay is 3.8-5.7 times higher than that of slower sprinters. The most interesting finding from the data is that Bolt had significantly lower leg stiffness than his two top competitors. The decrease in Bolt's lower leg stiffness is attributed to the larger ground contact times.
Force production - Fmax (kN) & Kvert (kN.m-1)
Of the three athletes analyzed, Bolt produced the largest force (3.6kN) during the race. When the athletes' force production in relation to their body weight is analyzed, Bolt's maximum force per unit of body weight is lower. However, this is where his larger body mass comes into play, naturally generating more force than a smaller individual. So due to his sheer size, Bolt is able to produce significantly more force than his top competitors.
Why is this important? A recent paper analyzed several international 100-meter races and athletes from 1987 through to 2012, including Bolt's 2009 World Record performance. They state, "The ability to maintain maximal speed until crossing the finish line during sprint running depends on the capability to maintain a high level of force production or power output despite the fatigue induced physiological and/or neural alterations."
This is backed up by their analysis. Maximal sprinting velocity (Vmax) and mean power (W/kg) produced over the 100-meter distance significantly influenced sprint performance—the ability to produce force at high speeds. World class performances require a maximal velocity for men of over 41.5 km per hour and 37.4 km per hour for women. Usain Bolt reached 43.9 km per hour in his World Record performance in 2009.
Here are the split times and velocities for Usain Bolt and Asafa Powell from Usain's 9.58-second record performance in 2009, taken from Applied Sprint Training, by James Smith .
Reaching a higher max velocity late in the race requires the ability to keep accelerating despite the increase in running velocity. Therefore, athletes need the ability to produce horizontal force from the ground at very high velocities. This is considered a crucial factor in 100-meter race performance. An increase in the duration of the acceleration phase allows athletes to reach Vmax later in the race, reducing the effect of fatigue on performance.
Bolt possesses all of these traits. He is able to reach a higher maximal velocity later in the race compared to other sprinters. As you can see from the charts, he reaches his maximum velocity at 70 meters (12.35m/s), while Powell reaches his at 60 meters (11.90m/s). Bolt accelerates longer than anyone else to a speed faster than anyone else, showcasing his ability to keep producing high amounts of horizontal force at very high velocities. This is why you often see him cruising to the finish line when other sprinters have started decelerating much earlier in the race.
The findings from Taylor and Beneke raise a number of questions about how we should train sprinters. Would training sprinters to sprint like Bolt create more world-class sprinters, or are his anthropometric characteristics simply so different from his competitors that it wouldn't make a difference? That's the million-dollar question.
HERE is an awesome interactive graphic showing the whole 100-meter final at the 2016 Olympics in Rio.
- Taylor, M., Beneke, R., "Spring Mass Characteristics of the Fastest Men on Earth." International Journal of Sports Medicine, 2012. 33: p. 667-670.
- Charles, J., Bejan, A., "The evolution of speed, size and shape in modern athletics." Journal of Experimental Biology, 2009. 212: p. 2419-2425.
- Watts, A., Coleman, I, Nevill, A., "The changing shape characteristics associated with success in world-class sprinters." Journal of Sports Science, 2011. 30(11): p. 1085-1095.
- Morin, J.B., Jennin, T, Chevallier, B, Belli, A., "Spring-mass model characteristics during sprint running: Correlation with performance and fatigue-induced changes." International Journal of Sports Medicine, 2006. 27: p. 158-165.
- Slawinski, J., Termoz, N, Rabita, G, Guilhem, G, Dorel, S, Morin, J.B, Samozino, P., "How 100-m event analyses improve our understanding of world-class men's and women's sprint performance." Scandinavian Journal of Medicine & Science in Sports, 2015. Epub.
- Smith, J., Applied Sprint Training. 2014.
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