Transcript How Fast Can Usain Bolt Run?

How Fast Can
Usain Bolt Run?
John D Barrow
World 100m record progression: men
Swimming Improvements are Vastly Greater
Men’s 400m run: 43.8 (1968) to 43.18 (2011)
Men’s 100m swim: 52.2 (1968) to 46.91 (2011)
Bolt’s 100m Record-breaking Progression
2008 Beijing Olympics 9.68 s
2010 Berlin World Championships 9.58 s
Final Time = Reaction Time + Run Time
Reaction Time less than +0.10 s = 100 millisecs
Means a false start and
Disqualification
Reaction time -0.104 s (before the gun!)
The ‘Gun’ is Not Good Enough
+ Starter’s position
5m
Sound speed = 340 m/s
Inside lane hears the gun
(15 -5)/340 = 0.029s
15m
earlier than outside lane
This really matters!
The straight 200m timekeeping problem
sound travel time was 1.7s.
Timekeepers reacted to the visual flash – not the sound
1960 Olympic Champion
(was very suspicious)
Armin Hary reaction 0.04s
!!
The ‘Anticipator’
Berlin World Championships
Bolt
Gay
Powell
Bailey
Thompson
Chambers
Burns
Patton
0.146 + 9.434 = 9.58
0.144 + 9.566 = 9.71
0.134 + 9.706 = 9.84
0.129 + 9.801 = 9.93
0.119 + 9.811 = 9.93
0.123 + 9.877 = 10.00
0.165 + 9.835 = 10.00
0.149 +10.191 = 10.34
Beijing Olympic final: Bolt’s
reaction time was 0.165s for his 9.69s total,
The other seven finalists reacted in
0.133, 0.134, 0.142, 0.145, 0.147,
0.165, and 0.169 sec.
Only one was slower than Bolt.
Quickest possible reaction is supposed to be 100 ms
DB Lipps et al
425 athletes. Male mean 168 ms with 160-178ms 95% CL
Female mean 191 ms with 180-205 ms 95% CL
Estimated absolute min for male 124 ms, for female 130 ms
Male sprinters made 25 false starts in Beijing -- only 4 by females
Should there be different false start criteria
for men and women??
False starting is not the Answer
Improvement Tip Number 1
Improve reaction time to 0.12 s and
9.58 s record improves to 9.55 s
Improve reaction time to 0.10 s and
9.58 s record improves to 9.53 s
Wind Assistance
Streamlining and Effective Body Area
Air Drag
 Speed V
Area, A(Bolt)
Mass of tube of air swept in time t is   A’  V  t = ma
 = air density
A’ = c  A(runner) is the ‘effective’ body area
c = drag factor
Drag force from still air = -maV /t = - c A V2
Drag force with wind speed W = - c A (V
Following wind is + and Headwind is –
-
W)2
Running around in the Wind
Drag force with wind speed W is  (V - W)2
Power needed = Force x velocity  (V - W)2 x V
Following wind is + and Headwind is –
Disadvantage of headwind and crosswind beats
the advantage of a tailwind of the same magnitude
KV(V+W)2
KV(V2+W2)
Lap
of square
track
Wind speed W in this direction
Runner runs at speed V in still air
KV
(V2+W2)
Power per lap = 4KV(V2 + W2 ) 4KV3
KV(V-W)3
It’s always slower running laps in the wind
Windy 400m- 10,000m races will be slower
A Wind-assisted Marathon
“It felt like there was no wind”  V = W
Drag force with wind speed W is - c A (V - W)2
Current record is 2:03:38, set by Patrick Makau on 25 Sept. 2011
Haile Gebrselassie’s old world record was 2hr 3m 57s
April 18th 2011 Geoffrey Mutai 2 hrs 3m 2s Boston marathon (Moses Mosop 4 s behind)
Downhill point-to-point courses can’t drop more than 42 m. Boston drops 139 m !
Winner’s average speed 5.7 m/s -- close to estimates of following wind on the course
 3% power saving
Equivalent to a still-air time of 2 hrs 6m 45s with the wind always at his back.
Bunched for first half so maybe only had benefit for second half (run in 61m 04s !!!)
This gives a corrected time of 2hr 4m 52s.
Allowing for wind assistance
in the 100m sprint
M = 70 kg
 = 1.19 kg/m3
A = 1.8  0.3 m2
c1
About 3% of effort is beating wind drag
T(W=0) = [1.03 – 0.03(1 – WT(W)/100)2]  T(W)
“It’s an ill wind …..”
Improvement Tip Number 2
Roughly 2 m/s of following wind reduces windless time by  0.1s
Bolt’s 9.58 s was set with W = 0.9 m/s
Improves to
9.49 s with faster reaction time
and a W = +2 m/s tailwind
The Women’s World Record
‘Flo-Jo’
10.49 s
??????
Florence Griffiths Joyner
was almost certainly wind-assisted!
A Case of Wind Gauge Failure ?
Wind gauge read 0.0 m/s in 1988 US Olympic trials semi-final
Neighbouring jumps were experiencing 4m/s tailwinds
and the next semi-final had 5 m/s tailwind
10.49s broke the record by 0.27s !!
Similar dramatic improvements by the others in the same race
‘Real’ record is 10.61s in the final with +0.9 m/s tailwind
High-Altitude Sprinting
Improvement Tip Number 3
Each 1000m of altitude produces a reduction in air density
worth about 0.03s over sea level for 100m sprinters
Mexico City was worth about 0.07s
Many actual records were improved by 1.7% in Mexico City
Improvements were much greater than air density effect alone
The Velodrome
Heated air at track level
Means
Faster cycling
Hot air rises !
Drag force from still air  air c A V2
Air Density Falls with Temperature
  (deg K)/T
Air Drag at Track Level in the London Velodrome
Drag Force  air × frontal area × V2
A new type of ‘wind-assisted’ performance
Worth 1.5 sec over 4K pursuit
Effortless Improvements for Bolt
1. Improve Reaction Time
2. Maximise legal wind assistance to 2 m/s
3. Race at high altitude (2250m)
‘Effortless’ Improvements for Bolt
His 9.58 s becomes
Reaction time improvement
 9.55 s
Maximise legal tailwind
 9.49 s
Race at max ‘legal’
high altitude (1000m)

9.46 s
Is Bolt The Fastest?
Blake: 19.26s - reaction time 0.27s = Run time of 18.99s
Bolt: 19.19s – reaction time 0.13 = Run Time of 19.06s
Usain Bolt’s average 100m is 9.530s
Yohan Blake’s average 100m is 9.495