Kinesiology 50(2018)2:172-180 Čoh, M. et al.: KINEMATICS OF USAIN BOLT’S MAXIMAL SPRINT VELOCITY 172 KINEMATICS OF USAIN BOLT’S MAXIMAL SPRINT VELOCITY Milan Čoh 1 , Kim Hébert-Losier 2 , Stanko Štuhec 1 , Vesna Babić 3 , and Matej Supej 1 1 University of Ljubljana Faculty of Sport, Slovenia 2 University of Waikato, Faculty of Health, Sport, and Human Performance, Adams Centre for High Performance, New Zealand 3 University of Zagreb, Faculty of Kinesiology, Croatia Original scientific paper https://doi.org/10.26582/k.50.2.10 UDC: 796.42:577 Abstract: This study investigated the maximal sprint velocity kinematics of the fastest 100 m sprinter Usain Bolt. Two high-speed video cameras recorded kinematics from 60- to 90-m marks during the men 100 m final at the IAAF World Challenge Zagreb 2011, Croatia. Despite a relatively slow reaction time (194 ms), Bolt won in 9.85 s (mean velocity: 10.15 m/s). His fastest 20-m section velocity was 12.14 m/s, reached between 70- and 90-m marks, by 2.70 m long strides and 4.36 strides/s frequency. At the maximal velocity, his contact and flight times were 86 and 145 ms, respectively, and vertical ground reaction force generated equalled 4.2 times his body weight (3932 N). The braking and propulsion phase represented 37% and 63% of ground contact, respectively, with his centre of mass (CoM) exhibiting minor reductions in horizontal velocity (2.7%) and minimal vertical displacement (4.9 cm) emerged Bolt’s maximal sprint velocity and international predominance from his coordinated motor abilities, power generation capacities, and effective technique. This study confirms that his maximal velocity was achieved by means of relatively long strides, minimal braking phase, high vertical ground reaction force, and minimal vertical displacement of CoM. This study is the first in-depth biomechanical analysis of Bolt’s maximal sprinting velocity with the segmental reconstruction. Key words: 100 m sprint, athletics, biomechanics, sport performance, sprint running Introduction Usain Bolt is one of the greatest athletes in the history of athletics. He is the winner of eight Olympic gold medals, as well as the world record holder in the 100 m (9.58 s), 200 m (19.19 s), and 4 x 100 m relay (36.84 s). During the 12 th International Association of Athletics Federations (IAAF) World Championships in Berlin in 2009, he established a new 100 m world record with a tailwind of 0.9 m/s, beating his previous world record by 0.11 s that had been set in 2008. Specifcally, his 100 m world record was one of the most remarkable achieve- ments in sprinting and was the largest improvement in the 100 m world record yet observed (Graubner & Nixdorf, 2011). Recently, at the 15 th IAAF World Championships in Beijing, 2015, Bolt managed to maintain his world titles in the 100 m, 200 m, and 4 x 100 m relay despite participating in few compe- titions prior to the Championships due to injury. Bolt’s performance has been a subject of numerous media analyses, debates, and discussions, as well as biomechanical investigations. Research literature has attempted to explain Bolt’s perfor- mance using spatio-temporal parameters (Graubner & Nixdorf, 2011; Maćkała & Mero, 2013), math- ematical and biomechanical models (Beneke & Taylor, 2010; Eriksen, Kristiansen, Langangen, & Wehus, 2009; Graubner & Nixdorf, 2011; Taylor & Beneke, 2012), as well as anthropometrical charac- teristics (Charles & Bejan, 2009; Maćkała & Mero, 2013). There has also been attempts to estimate Bolt’s 100 m sprinting potential (Barrow, 2012; Eriksen, et al., 2009), with a general consensus that he could have run below 9.5 s if only his reaction time had been better and under optimal environ- mental conditions (i.e., tailwind and high altitude), thus agreeing with the prediction by Denny (2008) that humans can run 100 m in 9.48 s. However, kine- matic data of Bolt running in competition are rare, and a more detailed investigation for Bolt’s whole- body kinematics could assist in verifying some of the numerous theories of his sprinting success. When Bolt set his current 9.58 s world record, his fastest 20-m section time was 1.61 s, refecting