The energy cost of sprint running and the role of metabolic power in setting top performances

TLDR: The above approach can yield useful information on the bioenergetics and biomechanics of accelerated/decelerated running on flat terrain and, on a 10 % down-sloping track Bolt could cover 100 m in 8.2 s.

Abstract: To estimate the energetics and biomechanics of accelerated/decelerated running on flat terrain based on its biomechanical similarity to constant speed running up/down an ‘equivalent slope’ dictated by the forward acceleration (a f). Time course of a f allows one to estimate: (1) energy cost of sprint running (C sr), from the known energy cost of uphill/downhill running, and (2) instantaneous (specific) mechanical accelerating power (P sp = a f × speed). In medium-level sprinters (MLS), C sr and metabolic power requirement (P met = C sr × speed) at the onset of a 100-m dash attain ≈50 J kg−1 m−1, as compared to ≈4 for running at constant speed, and ≈90 W kg−1. For Bolt’s current 100-m world record (9.58 s) the corresponding values attain ≈105 J kg−1 m−1 and ≈200 W kg−1. This approach, as applied by Osgnach et al. (Med Sci Sports Exerc 42:170–178, 2010) to data obtained by video-analysis during soccer games, has been implemented in portable GPS devices (GPEXE©), thus yielding P met throughout the match. Actual O2 consumed, estimated from P met assuming a monoexponential VO2 response (Patent Pending, TV2014A000074), was close to that determined by portable metabolic carts. Peak P sp (W kg−1) was 17.5 and 19.6 for MLS and elite soccer players, and 30 for Bolt. The ratio of horizontal to overall ground reaction force (per kg body mass) was ≈20 % larger, and its angle of application in respect to the horizontal ≈10° smaller, for Bolt, as compared to MLS. Finally, we estimated that, on a 10 % down-sloping track Bolt could cover 100 m in 8.2 s. The above approach can yield useful information on the bioenergetics and biomechanics of accelerated/decelerated running.