Abstract
ABSTRACTThis study investigated kinematics of human accelerated sprinting through 50 m and examined whether there is transition and changes in acceleration strategies during the entire acceleration phase. Twelve male sprinters performed a 60-m sprint, during which step-to-step kinematics were captured using 60 infrared cameras. To detect the transition during the acceleration phase, the mean height of the whole-body centre of gravity (CG) during the support phase was adopted as a measure. Detection methods found two transitions during the entire acceleration phase of maximal sprinting, and the acceleration phase could thus be divided into initial, middle, and final sections. Discriminable kinematic changes were found when the sprinters crossed the detected first transition—the foot contacting the ground in front of the CG, the knee-joint starting to flex during the support phase, terminating an increase in step frequency—and second transition—the termination of changes in body postures and the start of a slight decrease in the intensity of hip-joint movements, thus validating the employed methods. In each acceleration section, different contributions of lower-extremity segments to increase in the CG forward velocity—thigh and shank for the initial section, thigh, shank, and foot for the middle section, shank and foot for the final section—were verified, establishing different acceleration strategies during the entire acceleration phase. In conclusion, there are presumably two transitions during human maximal accelerated sprinting that divide the entire acceleration phase into three sections, and different acceleration strategies represented by the contributions of the segments for running speed are employed.
Highlights
Sprint running is a high-speed locomotion mode
The 100-m race time is strongly correlated with maximal sprinting speed during the race (Bruggemann and Glad, 1990; Mackala, 2007; Volkov and Lapin, 1979), and the time during which the sprinter can accelerate with maximal effort is limited to 5–7 seconds (Hirvonen et al, 1987; Margaria et al, 1966)
Breakpoint detection and transitions and sections of accelerated sprinting the presented methods partially failed to detect the breakpoints, we found discriminable changes in the kinematics of sprinters, representing the transition relating to the crossing of our determined breakpoints, which enhances the validity of our methods
Summary
Sprint running (sprinting) is a high-speed locomotion mode. The winner of the 100-m race at the highest competitive level is considered the fastest man or woman in the world at that time. The 100-m race time is strongly correlated with maximal sprinting speed during the race (Bruggemann and Glad, 1990; Mackala, 2007; Volkov and Lapin, 1979), and the time during which the sprinter can accelerate with maximal effort is limited to 5–7 seconds (Hirvonen et al, 1987; Margaria et al, 1966). Different manners of motions are recommended to sprint effectively; e.g. during the acceleration phase, speed development depends mainly on the powerful extensions of all major lower-extremity joints (Debaere et al, 2013b; Johnson and Buckley, 2001), and when the athlete reaches higher speeds, it is necessary to rotate the legs forwards and backwards relative to the hip joint and this limits a further increase in sprinting speed (van Ingen Schenau et al, 1994)
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