Osaka Biomechanics report on Gay & Powell
Mid-phase sprinting movements of Tyson Gay and Asafa Powell in the 100-m
race during the 2007 IAAF World Championships in Athletics
Akira Ito, Koji Fukuda and Kota Kijima
Osaka University of Health and Sport Sciences, Osaka, Japan
Abstract
In the present study, the running movements of Tyson Gay (9.85 seconds) and Asafa Powell (9.96
seconds) who finished first and third, respectively, in the 2007 IAAF World Championships in
Athletics were analyzed. Their data were compared to past data (Ito et al., 1998) in order to
determine the characteristics of both sprinters.
Maximal sprint running velocity was 11.85 m/s for Gay and 11.88 m/s for Powell. For Gay
and Powell, step frequency was 4.90 and 4.96 steps/s, respectively, and step length was 2.42 and
2.40 m, respectively. According to Ito et al. (1998), sprint running velocity is not related to maximum
thigh angle “high knee”, but the faster the sprint running velocity, the greater the minimum knee
angle. The maximum thigh angle for Gay and Powell was comparable at 65° and 70°, and the
minimum knee angle for Gay and Powell was 41° and 38°, respectively, and these numbers were
similar to the data obtained by Ito et al. (1998). The horizontal distance from the toe at the point of
landing to the center of gravity for the two sprinters was 0.31 m, and this number is comparable to
that for sprinters who run 100 meters in 11 seconds (Fukuda and Ito, 2004). Therefore, it is not
necessarily good to land immediately underneath the center of gravity when landing. In support leg
movements, an interesting finding was seen with maximum knee extension velocity for Gay and
Powell. During landing, the knee joint of both sprinters always remained bent, and when
acceleration force was expressed during the later half of the support phase, the extension velocity
had a negative value: -50 degrees/s for Gay and -68 degrees/s for Powell.
Training guidance that attempts to increase sprint running velocity by reducing the
deceleration associated with landing must be reexamined because the landing distance for Gay
and Powell is comparable to that of sprinters who run 100 m in 11 seconds. What is important here
is that Gay and Powell continue to bend the knee of the support leg during the support phase, and
training guidance that instructs sprinters to actively extend the knee and ankle joints of the support
leg must be reevaluated.
- Introduction
While the 100-m sprint is a simple sport, it requires athletes to compete by running at top
speed, and the winner of the 100-m sprint receives the greatest accolades in track and field. In
order to run the 100-m sprint with good results, fast reaction time after the start signal and acceleration after the start are important, but the most important element is maximum sprint running
velocity. World-class sprinters reach their maximum sprint running velocity in about 70-80 m (Ae
and Ito, 1992), and the maximum sprint running velocity of sprinters who run 100 m in less than 10
seconds is ≥11.8 m/s (Ito et al., 1998). Fast sprint running requires a strong body and efficient
running movements.
In the present study, the running movements of Tyson Gay (9.85 seconds) and Asafa
Powell (9.96 seconds) who finished first and third, respectively, in the 2007 IAAF World
Championships in Athletics were analyzed while they were running at top speed in the final race.
Their data were compared to past data (Ito et al., 1998) in order to determine the characteristics of
both sprinters. - Methods
During the final race for the men’s 100-m sprint event during the 2007 IAAF World
Championships in Athletics, two high-speed video cameras (Phantom v4, Vision Research Inc,
USA）were placed at the highest row of the spectator stands on the start line and on the finish line in
order to capture Tyson Gay and Asafa Powell at the 60-m mark. The two cameras were
synchronized and captured images at 100 Hz. Using motion analysis software (DKH, Tokyo, Japan),
the two-dimensional coordinates of 24 body points were scanned at 100 fps, and the direct linear
transformation method (DLT) was used to calculate three-dimensional coordinates where the x-axis
was the direction of sprinting, the y-axis the vertical direction perpendicular to the ground, and the
z-axis was the horizontal line parallel to the starting line. The error between calculated
three-dimensional coordinates and the actual values of the calibration points in the x, y and z-axis
directions was 0.005 m, 0.005 m and 0.005 m, respectively. The three-dimensional coordinates
were subjected to smoothing at 7 Hz using the Butterworth method.
For comparison, data accumulated from men’s 100-m sprint events in international
competitions and official Japanese track and field meets were used. Of our previous data, the best
sprint record was the 9.86 seconds that Carl Lewis ran at the 1991 IAAF World Championships in
Athletics in Tokyo. - Results and Discussion
Step frequency and step length
Sprint running velocity was determined based on the distance covered by the center of
gravity over two steps, and sprint running velocity at the measurement point was 11.85 m/s for Gay
and 11.88 m/s for Powell. Figure 1 shows the relationships among sprint running velocity, step
frequency and step length. According to past data (Ito et al., 1998), the faster the sprint running
velocity, the greater the step frequency and the larger the step length. For Gay and Powell, step frequency was 4.90 and 4.96 steps/s, respectively, and step length was 2.42 and 2.40 m,
respectively, and these numbers mostly agreed with past data. Gay is 1.83 m tall and Powell is 1.90
m tall, and the step length to height ratio for Gay and Powell is 1.32 and 1.26, respectively. Hence,
while Gay is a step-length type sprinter, Powell is a step-frequency type sprinter. When Carl Lewis
set the world record of 9.86 seconds in 1991, step frequency was 4.67 steps/s, step length 2.53 m
and step length-to-height ratio 1.35 (Ito et al., 1994).
(pics / graphs more info to follow)