Isn't a human with a stopwatch just as likely to hit the button early as they are late, for both the take off and the finish?
since in a 40 yd, you're reacting entirely to the movements and spatial position of the runner, wouldn't this be the case?
I realized I never really answered your question, the link below is a good explanation for why there needs to be a conversion from hand times to approximate an automatic time. The bottom line is as long as the human timers are reacting to the movement of the athlete, hand times will always be faster (shorter) than automatic times. I'm not familiar with the setup at say the NFL combine for timing 40s but it may well be that .14 seconds might be a more appropriate conversion than .24, it all depends on where the hand timers are relative to the athlete:
Ever since the 100m was added as an official event by the IAAF in 1912, the quest to run a sub 10 second 100 meter has been the benchmark for sprinting
yes, this is what i was looking for, i am trying to find how to accurately convert 100m times to 40 yard dash times that account for every variable, yet each of these conversions do not include the fact that a track makes you faster than turf, and the fact that spikes also make you faster than cleats.
In my opinion, the most accurate way to convert a 100m race (or 60m indoors) to 40 yards is to add up the 10m segment times if you have them, chopping the 30-40m segment to account for the shorter 40 yard distance (36.55 meters) so something like this:
It's still not a perfect conversion because obviously Bolt was still accelerating from 30 to 40 meters, but it's much better than some of the other nonsense I've seen. Now the question is what to do about the partial hand timed nature of typical 40 yard dash measurements? According to the speed endurance link I posted above we can convert using either .24 or .14, it really depends on where the timer is positioned. Taking those two conversions for Bolt's 2008 100m we get 3.945 or 4.045. Personally I think it's unlikely that the individual starting the clock at the combine is 100 meters or more away from the start, so a .14 second conversion time is probably closer to reality.
Another really interesting race was Su Bingtian's semi-final race from the Tokyo Olympics where he was timed at 6.29 at the 60m mark. Unfortunately we don't have 10m splits for that race but we do have 30m splits so we can do something similar:
[0-30m] - [reaction time] + [30-60m] * (6.55/30)
3.73-.142 + 2.56 * .2183 = 4.139 seconds
I realize that is really generous taking Bingtian's 30-60 time and using it to estimate the last 6.55 meters of a 40 yard dash but it's all we have in this case. I think we could estimate that Bolt and Bingtian would be really close at 40 yards, Bolt crossed the 30m mark in 3.615 and Bingtian in 3.588 after you take away their reaction times. I think Bingtian may have run a faster 40 yards than Bolt, but only by maybe .01 or .02 seconds.
Christian Coleman has run some fast 30m splits in some of his 100m but the fastest I can find was about 3.64 after taking away his reaction time, so it seems unlikely that any of Coleman's races were as fast as Bingtian's or Bolt's fastest 40 yards.
yes, this is what i was looking for, i am trying to find how to accurately convert 100m times to 40 yard dash times that account for every variable, yet each of these conversions do not include the fact that a track makes you faster than turf, and the fact that spikes also make you faster than cleats.
As far as accounting for turf and cleats etc. There is no real conversion for that. To take all those variables into account I think we need a different approach, like coming up with an average ratio between 40 yard times on turf in cleats and 100m times on a track in spikes. So for example with Bolt above we can say his ratio is (ignoring the fact he wasn't wearing cleats):
4.22/9.58 = 0.44
The problem with this approach is we rarely get an athletes 40 yard dash time and 100 meter sprint time at the same time in their career. For many NFL players the last time they ran a 100m was in high school, likely years before they ran their best 40 yards in the NFL combine. We can look at someone like DK Metcalf who's run a 100m more recently, here's his ratio:
4.33/10.36 = 0.417
That's actually not too far off of Bolt's conversion so we are likely already in the ballpark, at least for high performing athletes. Ultimately what we need to do is take a bunch of data points and come up with an average conversion. Ideally we would be able to find enough times that occurred roughly at the same time during an athlete's career, ie not comparing high school track times to NFL combine 40 yard dash times etc. We will also likely come up with a better conversion for a specific population of athletes for example high school football players may need a different conversion than college or pro players or between positions in football or between boys and girls etc.
The other issue is the way 40 yard dashes are timed are vastly different, there's no real standard so you will get a better number comparing FAT 100m times to one specific method of timing 40s. So for example if you are at a school and you time 40s a certain way for football you will want to come up with an average based on your situation. Even some automatic systems give variable results because athletes can trip light beams or lasers with different parts of their body (foot, leg, knee or torso), so to get any reasonable results you have to take an average of multiple attempts.
Once we have a reasonable ratio we can use that to estimate an individuals 40 yard dash time given their 100m time. So let's say that after averaging a bunch of data points you come up with a ratio of .42. If you have a kid that can run a 100m in 11.0 seconds flat, you can estimate his 40 yard time on turf would be around 11.0*.42 = 4.62 for 40 yards. Applying .42 to Bolt's WR 100m, 9.58*.42 we get 4.02 for 40 yards, that kind of jives with the calculations I did above. Honestly as a WAG .42 actually isn't a terrible conversion and probably isn't far from what a real average would give for many athletes.
Of course you could go crazy with statistics and come up with an equation based on a curve if you find a consistent variance over the range of 100m times compared to 40 yard dash times. Personally I don't think you are going to get much better numbers doing that than just coming up with a ratio for a population of athletes. Frankly most 40 yard dash times just aren't that accurate IMO to be worth the trouble.
