Speed is largely a function of genetics, confirms Dr David Marlin, the head of the International Conference on Equine Exercise Physiology, and an independent consultant based in Newmarket. Marlin says: "Horses that are very fast over five furlongs are likely to be born that way. You have to say that probably 80 to 90 per cent has to be what you started with."
It is all down to muscle, Marlin explains. What the naked eye sees, it can trust; the powerful shoulders and bulky hindquarters of the typical sprinter are mostly muscle, indicating speed. But this is not just any muscle.
In fact, all thoroughbreds have the same number of muscle fibres. It is the type of fibre that determines how fast a horse will be. Muscle fibres come in two types: Type I, or slow-twitch fibres, and Type II, or fast-twitch fibres. Slow-twitch fibres are the ones that can perform for hours on end without fatigue as they convert oxygen, slowly, into energy.
Horses in general have a much higher percentage of fast-twitch than slow-twitch fibres in their make-up, and thoroughbreds have a greater percentage of fast-twitch fibres than many other breeds. Within the thoroughbred, however, there is not much variation in the proportion of Type I and Type II fibres: individual variation is only about five per cent, with the proportion of Type II, or fast-twitch, fibres ranging from 85 to 90 per cent, says Marlin.
What it all comes down to is the kind of fast-twitch fibres a runner has. Again, there are two types: Type IIa and Type IIb. The percentage of IIb fibres could be as low as 10-15 per cent or as high as 90-95 per cent in any given thoroughbred. Both are fast-twitch fibres, but Type IIa is an intermediate sort of fibre, capable of both power and endurance, the main muscle used by horses such as Authorized and Yeats to produce the speed and stamina required for a Derby or a Gold Cup.
Type IIb fibres are the impatient cousin of IIa. Strong on flash but short on stamina, they create explosive speed and strength, literally without taking a breath. The cells in type IIb fibres can turn stored sugar, or glycogen, into energy without using oxygen. When they do so they create the by-product lactic acid. This is the quickest way to create energy, but it has a serious drawback.
"When horses accelerate out of the starting gate, the slowest system to adapt is the one using oxygen," says Marlin. "You've got to get the oxygen a distance of about two metres from nostril into muscle.To get to maximum oxygen uptake takes 40-50sec. So by the time the horse crosses the line in a 5f race, he's just about got the full oxygen to the muscle.
"But lactic acid can go from nothing to maximum in 1-2sec. If you couldn't produce lactic acid, you wouldn't be able to go fast. But you can't go far - it's a feedback method to keep you from damaging yourself."
Hence the stamina limitations of most very fast sprinters, which is the same reason even the best miler cannot sustain his top turn of foot for more than 3f or so. Sprinters can improve their efficiency through training, though. "You can improve it by high-intensity exercise," explains Marlin. "You can either produce more lactic acid, or the muscle can learn to tolerate lactic acid better."
HUMAN runners use a system called 'tapering', reducing their daily exercise beginning six or seven days before the race. "Sprinters tend to have much higher levels of glycogen in their muscle," says Marlin. "If you do a pipe-opener two days before the race, you could deplete the glycogen and maybe not replenish it."
Muscle glycogen could drop as much as 30 to 40 per cent in some fibres, he adds, but the fibres should recover in 24 to 48 hours. Research suggests that tapering works in horses, with a study in New Zealand showing that standardbreds who were tapered into races ran faster than those who did not.
This may explain why sprinters perform well with very little work between races. Indeed, Walker, Miss Andretti's vet, believes that some sprinters may be overtrained.
"Miss Andretti had one serious gallop and one moderately serious gallop in three weeks. The emphasis is on keeping them fresh," says Walker. Prior to her well-beaten run in the Golden Jubilee Stakes on Saturday, he said that the back-to-back Royal Ascot schedule was not the norm. "Four days between races for sprinters is not usual in Australia at all. You do like to spread them out a little more."
As it panned out, the races were too close together for Miss Andretti and Magnus, with the rain-soaked ground not helping matters. But Takeover Target bounced right back with a thrilling head second to the valiant Soldier's Tale. There is no getting around it - the Australians have something special when it comes to getting the most from their muscle.
The way Walker sees it, it all comes down to the human approach. "The most important individual contributing factor, the attitude underlying the whole thing, is probably what sets the tone," he says.
While last year's Golden Jubilee and July Cup hero Les Arcs came to sprinting late, after a less fruitful career over longer distances including a disastrous attempt over hurdles, such a scenario would be unlikely in Australia, says Walker.
"The speed - we don't take it out of these horses. We probably look to tap into their ability at an earlier age. Speed horses in Australia have class - they're all considered to have class. In Australia, we expect the majority of horses to perform over one mile or less, and it's only when they don't perform over shorter trips that they become stayers.
"Genetics plays a huge part, training the next biggest, then environmental factors," he adds. "Precocity is not considered the poor cousin it is in England. The thinking is probably a bit of the mirror image here."
