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[RC] Acceleration - Ridecamp Guest

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Authors PE diPrampero, S Fusi, L Sepulcri, JB Morin, A Belli, G Antonutto
Title   Sprint running: a new energetic approach
Full source     Journal of Experimental Biology, 2005, Vol 208, Iss 14, pp 

The speed of the initial 30 m of an all-out run from a stationary start on a 
flat track was determined for 12 medium level male sprinters by means of a 
radar device. The peak speed of 9.46  0.19 m s(-1) (mean  S.D.) was attained 
after about 5 s, the highest forward acceleration (a(f)), attained immediately 
after the start, amounting to 6.42  0.61 m s(-2). During acceleration, the 
runner's body (assumed to coincide with the segment joining the centre of mass 
and the point of contact foot terrain) must lean forward, as compared to 
constant speed running, by an angle alpha=arctang/a(f) (g=acceleration of 
gravity). The complement (90-alpha) is the angle, with respect to the 
horizontal, by which the terrain should be tilted upwards to bring the runner's 
body to a position identical to that of constant speed running. Therefore, 
accelerated running is similar to running at constant speed up an 'equivalent 
slope' ES=tan(90-alpha). Maximum ES was 0.643  0.059. Knowledge of ES allowed 
us to estimate the energy cost of sprint running (C-sr, J kg(-1) m(-1)) from 
literature data on the energy cost measured during uphill running at constant 
speed. Peak C-sr was 43.8  10.4 J kg(-1) m(-1); its average over the 
acceleration phase (30 m) was 10.7  0.59 J kg(-1) m(-1), as compared with 3.8 
for running at constant speed on flat terrain. The corresponding metabolic 
powers (in W kg(-1)) amounted to 91.9  20.5 (peak) and 61.0  4.7 (mean).

NOTE: This is a very interesting paper in that it gives a clue as to why uphill 
galloping repetitions seem to bring so much ?efficiency? to the equine gait on 
the flat.

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