It's Time To Split, Bolt

Sun Herald

Sunday September 14, 2008

By LEN JOHNSON

USAIN BOLT arrived home to a hero's welcome in Jamaica on Monday, his bright red BMW convertible mobbed on its way from the airport to a reception which, in turn, started more than two hours late.

By popular account, Bolt was almost as tardy getting through the final 20 metres of the Olympic 100 metres final. He won, in a world record 9.69 seconds, but the celebrations or showboating (choose according to personal prejudice) started well before that.

Somewhere between the 85m and 90m points, Bolt dropped his arms and spread them wide. Then, inside the last 10m, he successively thumped his right fist into the left side of his chest, twisted to the right and leaned back as he crossed the line.

Estimates of how much time Bolt "lost" through these gestures have varied almost as much as opinion on their appropriateness. His coach, Glen Mills, has been quoted as saying he could have run 9.52, though a closer reading of the reports suggests the question he was answering was how fast he might have run given perfect conditions and the maximum allowable tailwind.

In any case, 9.52 is a pretty scary notion. One scientific study backs up such a time, but only as the lower limit after making two assumptions, both with an error rate of plus or minus 0.04 seconds.

The far more likely scenario is Bolt's slowdown was not marked at all, costing him perhaps as little as 0.02, perhaps as much as 0.07.

Paul Hallam, Australian national event co-ordinator for sprints and relays, is puzzled by the 9.52 estimate, which has gained currency on athletics websites thanks to the original story quoting Mills.

"In a perfect world, he may have run 9.52," Hallam says. "Even if all the planets aligned, however, it is doubtful. I think 9.63 is probably more to the mark."

Even getting there takes some heavy assumptions, and the base date is shifty. At a world championships, the IAAF and the local organising committee normally provide biomechanical analysis of events. This first gained some public notoriety at the Athens world championships in 1997, when laser guns were used to measure speeds. The guns, we were promised, would show unequivocally who was the world's fastest man. Well, Maurice Greene dethroned Olympic champion Donovan Bailey in the 100m final all right, but their top speeds were identical to the nearest hundredth of a metre per second.

There are two known lots of unofficial 10m by 10m split times for the Beijing 100m final. The first, on the sprint website speedendurance.com, suggests a more radical slowdown than the second, reportedly from the high-performance team at USA Track and Field, the governing body for the sport in the US.

On the speedendurance.com figures, Bolt hit top speed at the halfway point and ran three consecutive 10m segments in 0.82 seconds (12.2m per second). He then slowed to 0.83 (80-90mps) and, more dramatically, to 0.90 (90-100mps).

The USATF splits, cited by Track & Field News magazine editor E. Garry Hill on the magazine's forum, concur with the top speed, but suggest Bolt hit it at the 40m mark and then slowed "only" to 0.84, 0.86 and 0.87 in his last three 10m segments.

The first figures bear out the impression of the Beijing naked eye; the second are in line with the consistent pattern of many, many 100m races over the years.

"All sprinters slow down," says Hallam of the last 20 to 30m. Bolt's relaxing, he adds, may actually have limited any slowdown. "Typically, in the last 10m, sprinters tend to be over-striding as they reach for the line, the stride frequency drops off and they lose some form.

"While he [Bolt] slowed down, he had such good momentum it wouldn't have cost him much."

Hallam took video of Patrick Johnson at this year's national championships in Brisbane where he ran 10.31 in the heats, despite an obvious "shutdown" almost as marked as that of Bolt. When Hallam examined the tapes, they told another tale. The slowdown cost Johnson only 0.02 to 0.03.

Taking the two breakdowns of the Beijing 100m, and assuming a drop-off of 0.01 to 0.02 for Bolt's last two 10-metre segments even had he run hard all the way to the line, Bolt would have run 9.63 or 9.64 using the more generous figures, 9.65 or 9.66 using the slower version of his splits. The analysis gets more interesting when you factor in wind assistance. Bolt's run had a nil wind reading.

A 1.0mps tailwind equates to a boost of about 0.06, a 2.0 (the maximum for record purposes) to 0.1. The wind is read at one point on the track (on the infield at the 50-metre mark), but give Bolt a +2.0 "wall of wind" throughout the entire 100 metres and suddenly a sub-9.60 time becomes at least a theoretical possibility.

© 2008 Sun Herald

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