Sprinters And Stayers
Whether a racehorse is better over short or long distances depends largely on its breeding, and the type
of muscle fibres that it has inherited from its sire and dam. Sprint-bred horses have a high ratio of
fast-twitch fibres, whereas in horses bred to stay slow-twitch fibres predominate. Fast-twitch fibres have
greater contractile strength, contract more rapidly and are larger in size than slow-twitch fibres. The
drawback is that lactic acid, which causes soreness and fatigue, builds up more quickly in fast-twitch fibres.
Because of the difference in appearance between fast-twitch and slow-twitch muscle fibres, a horse’s
overall body shape can help us to distinguish the sprinter from the stayer. Used in conjunction with its
breeding this will give a strong clue as to a horse’s preferred racing distance.
The typical sprinter is compact, with a relatively short back and powerful, rounded hindquarters. It has
well-muscled shoulders, and is strong through the loins (the lumbar area of the back, between the last rib
and the front of the pelvis) and gaskins (the area between the stifle and the hock). Compared with the stayer,
the sprinter often has shorter, more upright pasterns (the bones between the fetlock joint and the foot); short
cannon bones and a relatively long forearm; it has a shorter, more bulky neck; a deeper girth and, possibly,
shorter legs. The sprinter may have ‘downhill’ balance; that is, the croup may be higher than the withers. This
body type is designed for sheer speed rather than agility.
This colt, with his powerful sprinter’s quarters, was sired by the top-class stallion Oasis Dream. A strong
influence for speed, Oasis Dream won three Group 1 sprints, including the July Cup and the Nunthorpe Stakes.
Another typical sprinter, with his strong quarters, short back and muscular shoulder. He’s by Kodiac, a
prolific sire of good two year olds, whose progeny tend to be smallish, tough and hardy.
Compared with the sprinter, the stayer will have a longer, leaner musculature through his body and back. He
may have longer legs, and thus may be slightly taller. This body shape allows for a more fluid stride. The
stride is not as quick as that of the sprinter, and the longer-backed horse will lack the sprinter’s explosive
acceleration. But the stayer can carry that longer stride over a greater distance without tiring. The ideal
stayer will have long withers and well-sprung, rounded ribs. Whereas the sprinter often has a steeper angle to
his rump, the stayer’s is more level.
The grey filly in the photo above has the typical conformation of a stayer. She’s by Mastercraftsman, who won
the Irish 2000 Guineas, and is the sire of French Derby winner The Grey Gatsby. His stock tend to be late
maturing and are best at distances beyond a mile.