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Modern Riding Style Improves Horse Racing Times

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Science  17 Jul 2009:
Vol. 325, Issue 5938, pp. 289
DOI: 10.1126/science.1174605

Abstract

When animals carry loads, there is a proportionate increase in metabolic cost, and in humans this increase in cost is reduced when the load is elastically coupled to the load bearer. Major horse race times and records improved by 5 to 7% around 1900 when jockeys adopted a crouched posture. We show that jockeys move to isolate themselves from the movement of their mount. This would be difficult or impossible with a seated or upright, straight-legged posture. This isolation means that the horse supports the jockey’s body weight but does not have to move the jockey through each cyclical stride path. This posture requires substantial work by jockeys, who have near-maximum heart rates during racing.

Horse racing has existed in its current form for over 200 years. The apparently uncomfortable modern race riding posture was developed in the United States in the late 19th century, introduced to the United Kingdom in 1897, and universally adopted by 1910. This change in riding style (Fig. 1, A and B) corresponds to a dramatic improvement of 5 to 7% in race times in the United States between 1890 and 1900 and in the United Kingdom between 1897 and 1910 (fig. S1), strongly suggesting that the adopted posture benefits racing performance. This improvement is greater than that observed over the following century.

Fig. 1

(A) Jockeys demonstrating the traditional riding style in the United Kingdom (finish photo of 1900 Derby Stakes). [Reprinted from (11)] (B) The “martini glass” posture in modern thoroughbred racing (2008 Epsom Derby Stakes). [Credit: Tom Stanhope, Equine Action Images, www.equine-action-images.com] (C) Fore-aft (or craniocaudal, CC) and vertical (or dorsoventral, DV) movement of jockey (top left, green) and horse (bottom left, dark blue) with respect to constant velocity motion; movement of jockey relative to horse (middle right, light blue). Black lines indicate mean stride, and arrows, direction of movement. Phase in relation to contact of nonlead front leg (0%) is denoted by dots at 10% of stride values on the mean trajectory; air phase around 40 to 60%. Horses show larger amplitudes than jockeys, notably in the fore-aft direction. Horse and relative jockey movement are about 180° out of phase.

A jockey represents about 13% (~60 kg) of a horse’s body mass (~450 kg), and both conventionally seated riders and sandbags elicit an increase in mechanical and metabolic cost proportionate to the mass of the load (1, 2). When weight is added to racehorses’ saddlecloths to handicap them, a proportionate reduction in racing speed is observed (3). A backpack frame that elastically rather than tightly couples the load to the wearer reduces the cost of load carrying, possibly attributed to a reduction in the vertical movement of the backpack and hence the potential energy changes that the wearer’s legs must produce (4).

Changes in kinetic energy and gravitational potential energy of a horse during each stride of gallop are substantial (5) and may be associated with the metabolic cost of galloping (6), despite energy-storing, springlike legs (7). We hypothesize that a jockey (Fig. 1B) uncouples himself from the horse by moving relative to his mount. Fast-running quadrupeds appear insensitive to increases in weight (effective gravity) (8), but increased inertia (with weight) is detrimental to athletic performance (13).

We measured acceleration and calculated displacement of horse (and jockey) by using Global Positioning System and two inertial sensors (9). Horse displacement was found to be 150 ± 8 mm vertically, and 100 ± 7 mm in the fore-aft direction; jockey displacement was 60 ± 9 mm vertically, and 20 ± 4 mm in the fore-aft direction (Fig. 1C). The jockey’s body moves little with respect to a world inertial frame, and therefore the horse supports the jockey’s weight but does not have to accelerate and decelerate him or her through each stride cycle (Fig. 1C, top left). The jockey’s legs oscillate in length while transmitting a vertical force fluctuating about the jockey’s body weight, resulting in substantial mechanical work by the jockey (10). Interestingly, the jockey slightly overcompensates for the horse’s motion (Fig. 1C). Thus, displacement and velocity (hence kinetic energy) fluctuations of the jockey plus horse system might be slightly smaller than that of the horse alone, and the jockey could possibly “drive” the horse.

The crouched posture may confer an additional small reduction in aerodynamic drag [≤130 W mechanical power (9); <2% horse mechanical work at gallop (8)], but the modern posture is high on the horse (Fig. 1B) so there is little change in frontal area and drag reduction is unlikely to be the primary goal or benefit (compare with a track cyclist’s posture).

Supporting Online Material

www.sciencemag.org/cgi/content/full/325/5938/289/DC1

Materials and Methods

Figs. S1 and S2

References

References and Notes

  1. Materials and methods are available as supporting material on Science Online.
  2. We thank P. J. Hobbs for the horses; T. Cox, the Cox Library, and T. Stanhope, Equine Action Images, for photographs; the Horserace Betting Levy Board for funding (T.P., A.S., and M.F.); and the Bremer Ausbildungs Partnerschaft (international LEONARDO program) for funding (S.S.). The UK Biotechnology and Biological Sciences Research Council funded the technology development. A.W. holds a Royal Society Wolfson Research Merit award. A.W. and T.P. have filed a patent application on monitoring of horses and jockeys during racing with methods similar to those described here.
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