Thursday, August 6, 2009

Video Analysis of Sprinting: From the Start

In the 100m and 200m track sprinting events, the start can win or lose a race. In the 100m the winning difference is often measured in 100ths of a second, therefore any advantage that can be gained at the start could be crucial.

At the IAAF World Championships next week, Tyson Gay will take on Usain Bolt for the title of worlds fastest man. So far in 2009 both athletes have put up some impressive times and the first meeting between them this year should be fast, close and exciting. Usain Bolt is the Olympic champion and world record holder. We have previously discussed how fast he could possibly run. Tyson Gay is the reigning World Champion and recently ran the 100m in 9.75 seconds at the US Championships.

With both athletes being at the top of their game, victory may be decided by their start. Neither of them is known for their explosive or fast starts. Bolt has an incredibly long stride length and eats up ground with each step while Gay has unmatched leg speed. The start though is crucial and we have therefore decided to look at some video and examine the start.

Below is some front on video of Tyson Gay at the US Championships. We want to focus on his start.

A good start requires that the athlete sets up correctly. Here are some key factors for the set position before the start gun sounds.
  1. The hands are set up on the line and the shoulders and upper body should lean forward over the hands. Track coaches suggest an angle of about 15 degrees (The angle between the shoulders and hands and the vertical). Although we cannot see the angle at which Gay is leaning (this would need a side on view of his start), we can see that he is leaning forward and ready to explode from the blocks.
  2. The angle of the knees in the start position must allow the athlete to push away from the blocks with as much power as possible while at the same time being able to get their feet through to begin running. The optimal bend of the front knee should be around 90 degrees to provide the biggest lever to produce push off. The back leg needs to be bent less than this at about 60 degree so that it is able to still push off hard but will straighten before the front leg and have time to come through for the first step.
  3. Both legs need to push off almost simultaneously at the start of the race. The athlete cannot be sitting back on either his front or back leg at the start.
Tyson Gay sets up well and in this video he explodes from the blocks, pushing off with both legs quickly. Both legs straighten completely, with the rear leg leaving the blocks and starting to drive through before his front leg (left leg) is completely straight.

Gay also uses his arms to explode out of the blocks, as well as maintain good balance. Watch as his right arm drives backward and his left forward. This motion provides extra forward momentum, but it also ensures that as he starts he does not fall over to one side. The arms act as a counter balance to the motion of the legs. In this start his right leg will take the first step on the track and therefore his left arm needs to be forward to balance this motion.

Moving forward to that first right foot step on the track, we can see that Gay's head and chest are still down low. His arms are driving hard and fast. If you pause the video you will see them as a blur. We can also see that his first step is not too long. In fact his head, chest and hips all remain in front of his foot for this first step. This allows him to continue to stay low with his body. If he took a longer first step, it would force his chest up, which would in turn slow down his speed. His chest and head stay down for as many as 16 steps allowing him to lean forward during this start and continue to accelerate.

His start technique looks great here and although we do not know what his reaction time to the gun was, we can see that he was able to accelerate well from the start and this is why he put up such a fast time.

As I looked through more videos on Tyson Gay's start, I came across one from tttjump that suggested that Gay's knee rolls forward at the start. If you study the slow motion of the start in the video above you will see what this means. Gay's front leg (his left) moves forward and down, in fact bends a little more, just after the start and as his hands leave the ground.

The suggestion is that this extra bend of the front knee at the gun, causes a delay in his ability to get off the blocks. On closer examination we can see that his back foot is driving already (straightening) as his front knee "rolls" forward. This may be causing him to push off with less power from his back leg as he may need to slow it down, to give the right leg time to get into a position to start its push off.

From a biomechanical standpoint, this would suggest that Gay's front leg is not bent to the most optimal position to explode out of the blocks. He may be bending it a little more after the start to get more push off power. The split second it takes to bend the knee that little bit more and the small amount of back foot push off power that he may lose, could determine the outcome of the race against a phenom like Usain Bolt.

Once again from the standpoint of biomechanics, this problem could possibly be solved by simply adjusting Tyson Gays starting blocks or position slightly, allowing his front knee to set up in a more optimal position for his starting style.

Of course for this World Championships, it is too late to make any changes and Tyson Gay should provide Usain Bolt some really stiff competition when they hopefully meet in the final in Berlin.

If you will be watching or filming some video of any of the action at the IAAF world championships and would like to share some video for analysis, please let us know.

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