OK - I've been spending way too much time watching the Olympics. The fact that all of the events are being streamed has had an impact on the amount of work I've been able to accomplish, so I'm writing off some of this as vacation time.
I tend to be interested in sports I've had some involvement with - either by participation (and never at a terribly athletic level), through the involvement of a friend or relative, or by getting involved in the science behind a sport.1
I had asked for suggestions of science of sport questions people might have and a few people responded. Ted asked about the remarkable long jump record set by Bob Beamon. According to the always infallible Wikipedia, he came to the event as a favorite with a personal best of 8.33 meters - very close to the world record at the time. Somehow he managed 8.90 meters - 29 feet 2.5 inches - over 21 inches longer than the world record at the time. This was such a huge increase over everyone else in the world - and himself - that it stood out and remained the record until 1991 when Mike Powell jumped a 8.95 meters. Beamon still has the second longest jump in history, although a few have approached it.
Ted asked about what might be going on - after all - records were falling for jumping and sprinting events, while distance events saw terrible performance.
Mexico City is 2,240 meters above sea level and oxygen absorption by the human body is only about 90% what the athlete can manage at sea level. Athletes who had spent time training at altitude were able to absorb somewhat more than athletes who weren't acclimatized with the distance events being dominated by runners from high altitudes, although the times were not fast compared with sea level performances. Sprinting events, on the other hand, saw a lot of new records.
It turns out oxygen absorption isn't very important in sprinting events. During the burst of speed of a flat out sprint, the muscles are converting chemical to mechanical energy by anaerobic metabolism.2 In other words it makes sense that anaerobic events shouldn't be degraded, while aerobic events will.
The atmosphere has a lower density at greater altitude above sea level. At 20° C air density is 1.23 kilograms per cubic meter at sea level, but Mexico City is down to 0.98. Although the density is only 80% of sea level, you will only see a 0.1% drop in your sprint time, while many of the winning sprinters saw improvements in the 1 to 2% range.3 Further analysis suggests the real culprit was the wind.
The winds at Mexico City were largely behind the athletes for the 100 and 200 meter events and were high - bordering on, and possibly exceeding, the 2.0 meter per second limit requirement for official Olympic records. Precise weather data was not recorded and it is impossible to make absolute statements, but tail winds of this speed turn out to be enough to account for the improvements several athletes saw and there was a suspicion that they may have much stronger at times.4
For all endurance events athletes who had trained at altitude had a big advantage over those who did not. Since'68 some athletes train at altitude as the body learns to absorb more oxygen at the lower air pressure. The effect is short-lived and needs to be properly timed for best effect. Probably more common these days is sleeping in oxygen tents that simulate high altitudes.
The wind does have an impact on many events though - and perhaps technique should vary to take it into account. Imagine a longer race with a windspeed of w and runners pushing along at a constant speed v. For sake of argument think of them as running a square lap with legs that have a north, west, south and east alignment and have the wind coming from the north. When a runner is going north she will have an effective windspeed of v+w and when she is going south v-w. The force she feels will be proportional to (v+w)2 on the north leg (v-w)2 on the south and just v2 on the east and west portions. As long as the magnitude of v is greater than that of w, the total force for the race will be greater than it would be if the conditions were calm - she has to work harder to keep up the same pace.
Fortunately this is fine and dandy if all of the runners are experiencing the same conditions. And there are some tricks you can play. If you run directly behind another runner your effective airspeed, and thus air resistance, is less than that of an exposed runner. Runners and cyclists often bunch in packs to take advantage of this and the leader is at a big disadvantage.
But what if there is a trailing wind? I rarely see athletes take advantage of this and I've mentioned it to a couple of Olympic coaches. The runner (or cyclist) with the most wind at their back has an advantage, but those in the pack no longer benefit from the trailing wind. A better strategy would seem to be to break out of the pack. I was told the athletes don't know the wind velocity at any moment and windspeeds in these races is usually too low from them to take chances.
But what about Bob's miracle record-smashing jump? I found a few papers on the subject. The greater speed from the tail wind he probably had was probably enough to account for about half the extra distance. The rest probably came from his athleticism and perhaps a variation on his techniques. The fact that another person was able to better it in a calm shows that the record was humanly possible - he was able to muster the magic of doing it 23 years earlier than improvements in training and technique would suggest.
This is the beauty of sport - when someone manages to tap what seems impossible and astound the world.
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1 I'm very slow, but can have a bit of endurance. When I actively cycled centuries (100 mile rides) were no big deal. My niece Magi also is a red muscle (slow twitch) person, but she is a genuine athlete. She does marathons and is a nationally ranked ultra-marathon runner, racing in the mountains. Ultra-marathons usually start at 50 miles - yikes!
Pip and Dave - and probably others among you - have run marathons and Jheri is a "purely for the fun of it" runner who knocked off a 2:58 marathon the first time she tried one.
Colleen is exceptionally athletic having been a Division 1 All American in volleyball when she was in college and then moving on to pro indoor volleyball in Europe and finally pro beach volleyball. She taught me a lot about the sport and it is one of the main Olympic attractions for me.
2 It is a bit beyond a short post, but there are two types of anaerobic (without oxygen) metabolism. Both provide mechanical energy that greatly exceeds what aerobic metabolism can provide. Different muscle types are specialized for one or the other. White muscle is good for anaerobic metabolism, while red muscle (it looks red due to the oxygenated blood in it) is better suited for the long haul. Most people have 50:50 mixtures - but people good at endurance running can have as much as 80% red muscle, and 100 yard dash specialists can have about 75% white muscle. Usain Bolt could never run a marathon - at least not with a credible amateur time. This leads to a lot of interesting questions about body type and genetics in sport at the amateur, pro and world class levels.
A note on sub 10 second 100 meter races. The runners produce power at 2,500 to 3,000 watts. This is above and beyond the normal 70 or so watts used to keep the body functioning, but not physically moving. There is no way this heat can be immediately removed (for comparison the electric element on a stovetop is about 1,500 watts) and the internal body temperature soars. If the race was as long as 20 seconds at that level most of the runners would probably die from heat effects. Fortunately muscles can only function at this level for about 10 seconds. The 200 meter races are very different from 100 meters, even though both are sprints.
3 Offered without derivation - there is quite a bit of physics behind this number.
4 Again more physics, but a 2 meter/s following wind gives approximately a 0.12 second improvement for a 100 meter dash about twice that for 200 meters.
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