The biological basis of racehorse power courtesy James Willougby

The biological basis of racehorse power
Some while ago, I promised you a look at the science of how racehorses achieve fast times. At each distance, a horse requires a particular combination of speed and stamina, derived from the type of muscles it has and the blend of energy sources it can call on.To reach an advanced understand of the topic, so the true meaning of a horse's sectional times becomes more apparent, it is necessary to revert to biology which we all probably learned at school but have long since forgotten.A racehorse powers its movement by converting chemical energy stored in its muscles to mechanical energy for propulsion. The speed and efficiency with which it can do this is a significant factor of its racing merit.This chemical energy comes from adenosine triphosphate (ATP). When a chemical reaction occurs within the bonds of this molecule, energy is released which is used to contract muscle proteins and therby power movement.When a horse is at rest, its muscles have a residual stock of ATP which instantly fires the whole process, but the fuels it needs for prolonged movement are predominately fats and sugars.After a very short while, a horse's body needs to generate more ATP to meet the demands of the race. How it does this should provide you with a better insight of the way horses meet the demands of running overvarious distances, and how their capabilities can be inferred from studying their sectional times.To begin, I am going to take the example of two champion horses who won at the latest Breeders' Cup meeting, Classic winner Raven's Pass and Sprint hero Midnight Lute.These are the sectional times recorded by the leader at each point of call in their respective races on the Pro-Ride surface at Santa Anita:Sprint (6f) 21.28/43.85/55.14 = 1:07.08Classic (1m2f) 23.77/47.60/1:11.64/1:35.48 = 1:59.27Both races produced extraordinary finishing times which only world-class horses could achieve under the conditions which prevailed on the day. It is therefore hard to believe that either could have run much faster.So, according to the fundamental law of pace - even pace begets optimal time - it stands to reason that both races were run at even pace, right?Wrong. The Classic splits do indeed follow a pace of roughly 12 seconds per furlongs. At ten furlongs - which a scientific understanding leads me to believe is the purest test of the Classic thoroughbred - this "beat of 12" is characteristic of 99% of all the great time performances ever achieved. Though a horse's run-style may vary around this tempo - the slow early-fast late predilection of the true miler Raven's Pass is a good example - a horse simply cannot run its optimum time at 10 furlongs without a race of this shape around it.But, what of the brilliant sprinter Midnight Lute? The fractions of the Sprint were nothing like even, yet he, the runner-up Fatal Bullet and third-placed Street Boss all produced career-best Beyer speed figures, despite having markedly different styles of running.So, why do all top sprint races seem to follow a fast early-slow late pattern? Couldn't these horses run much faster times if they simply went off a bit more evenly?The answer is no. And, when you understand the reason, it may provide you with a whole new depth of interest in the sport.Let's return to biology 101. A horse's muscles, hungry for ATP, use three main processes to generate it, each making a different contribution to the horse's capacity to accelerate, sprint and stay.When the horse jumps out of the stalls, the residual ATP in its muscles combines with the breakdown of a molecule called phosphocreatine (PC) to provide enough fuel for the first 15 seconds of the race. This is extremely explosive, powerul energy which provides the horse with power like no other source.So a sprinter is usually going to run his first quarter-mile quicker than any other because he will never have the same magnitude of power to call on.
(Actually, Midnight Lute is a rare exception to this; his fastest quarter-mile in the Sprint was the middle one, but every other horse showed a pattern of marked deceleration, including runner-up Fatal Bullet.)Unfortunately, the extraordinary burst of acceleration of the sprinter leaving the stalls is not going to last. Within 15 to 20 seconds - approaching the end of the first quarter-mile - the readily available ATP/PC combination has run out and a second mechanism is about to take over.This process is called anaerobic glycolysis;'anaerobic' basically meaning without the presence of oxygen. A series of chemical reactions converts a fat molecule called glycogen into ATP in order to sustain the first explosive movement. Now, the world-class Midnight Lute is settling into the beat of his giant stride and the beautifully ridden Raven's Pass has hit his cruising speed. But what happens to them as the furlongs go by?To answer that question we need to consider the one big advantage and twoserious disadvantages of anaerobic glycolysis.As the name suggests, this second process of generating ATP does not require oxygen. This is tremendous news as the combination of heart and lungs used to move oxygenated blood to the extremeties takes time. It would be no good if that initial burst were wasted; the horse needs a second, ready source of power right now.But the first big disadvantage of anaerobic glycolysis is that it does not use much of the chemcial energy available from the fatty glycogen molecule. Only about 8%, in fact.
And the second drawback is worse still. The chemical reactions used to liberate the energy are extrememly dirty, creating waste products which start to eat away at the efficiency of the whole process.The most serious of these waste products is a substance called pyruvic acid. If this were to build up, the metabolic pathway from glycogen to ATP would grind to a halt. So the horse's body finds a temporary solution by converting pyruvic acid to less dangerous lactic acid, but even this has a severely limiting effect on the enzymes which the muscle relies upon. As you will know from personal experience of exercise, lactic acid build-up leads to muscle fatigue characterised by a burning, aching sensation in the athlete.
This is the infamous "pain barrier" to which Aidan O'Brien is fond of referring when discussing how he manages the psycholgical needs of the many champion racehorses he develops. (The "Red Zone" concept he introduced in a recent fascinating interview on RUK needs to be fleshed out more, and will be so when time allows.) Once this lactic acid build-up begins, it never ends. It is so powerful, so destructive to the metabolic pathway from glycogen to ATP that some biologists say a horse would be brought to a complete stop if this process alone were relied upon. Thesolution is to find a third mechanism for ATP conversion which is less messy and can allow the lactic acid accumulation to slow. This is known as aerobic glycolysis, but it does not kick in until a racehorse has been galloping for more than 60 seconds.Aerobic glycolysis ( 'with oxygen') may be slow but, boy, is a lot more efficient than its cousin. It generates the largest amount of ATP from each glycolgen molecule and is a much, much cleaner process for the metabolic pathway.In fact, the pyruvic acid produced this way is completely broken down into safer products, water and carbon dioxide being the only residue. And there is better news, still.As aerobic glycolysis continues, the bloodstream brings glocuse - primed for conversion to ATP - from glycogen stored in the liver and other fatty tissues of the body. (This is why sustained exercise is most efficient in helping to lose weight. When we can get offour glycogen-rich posteriors, of course.)Now, the smoothly ridden Raven's Pass is really beginning to pour it on, using lovely clean energy to limit the build-up of lactic acid and leave his muscles comparatively free to unleash afinishing kick.Oh, but what about Midnight Lute? He has finished the race already. In the 1:07 of the Breeders' Cup Sprint, he never had the chance to even call on the oxygen taken in by his lungs.But, of course, it doesn't matter. Garrett Gomez is standing up in the irons; he is punching the air. Midnight Lute has won a second Breeders' Cup Sprint with a brazen display of anaerobic glycolysis. He can ease down and his muscles can relax.
Who cares about lactic acid now, when adrenalin is surging through his body and his senses are overloaded by the cheering crowd, the blinking lights all around, even perhaps the thrill of exploring his athletic prowess? For a sprinter, even a late-running one like Midnight Lute, the best way to achieve a fast time is to sustain the initial burst provided by the PC kick detailed above; there is just no time for oxygenated blood to reach the muscles. The only way to keep up the gallop is to use ATP derived from dirty anerobic glycolysis. By the end of the six furlongs, the whole metablic pathway is a mess. But there is no time for anything else, and it doesn't matter anyway when the winning line is reached. And this is why sprints do not follow even pace. Exactly why a horse is a sprinter - they are made as well as born - wil be examined in the next article. For now, let's return to Raven's Pass.After a minute of the Breeders' Cup Classic - roughly five furlongs - here comes the lovely oxygenated blood and the glucose to power the muscles of Raven's Pass. Aerobic metabolism takes over in the second half of the Classic and lactic acid build-upslows. But aerobic metabolism alone cannot meet all the demands of his muscles, and some of the dirty anaerobic process continues. But jockey Frankie Dettori can keep this to a minimum by maintaining a constant speed (or near to) on Raven's Pass, using his energy most cleanly and most efficiently.And this is why middle-distance races follow even pace more closely than sprints. In the two minutes or so it takes to run a top race over 10 furlongs, the most efficient combination of a horse's different sources of energy is achieved while it runs at constant speed. This way it minimises the build-up of lactic acid while the process triggered by the arrival of oxgenated blood and glucose takes time to kick in.At distances in between six furlongs and 10 furlongs, the percentage use of aerobic and anaerobic respiration varies in proportion to the time taken to complete the race. One of the reasons why seven furlongs is a specialist distance for a horse is that it requires about one minute, 25 seconds of effort, which is on the threshold of aerobic metabolism. This necessitates an unusual demand; the true 7f specialist may be able to switch over to aerobic glycolysis faster and more efficiently than either the sprinter stepping up on distance or the miler stepping down.At distances of a mile and a half or more, a particularly interesting thing starts to happen, which can easily be seen in the sectionals of great races. I'm going to save that for next time, particularly as it led me to a finding which I believe is unique in the study of the thoroughbred.Thanks very much if you got this far. I hope you enjoyed the article and the others which will follow in this series. Apologies for the length of this piece: there is an awful lot to get through.
JW

Hennessy - Leop Feb - trends courtesy Tony Keenan

Official ratings have been a fabulous guide here. 9 of the last 11 winners here were rated at least 160 with one of the exceptions, Beef Or Salmon in 2003, yet to have been given a handicap mark; he had however won the Lexus on his most recent start achieving a Racing Post Rating of 163+.- The last 10 winners have been aged between 7 and 12 which is hardly much of a help. 9yos have won been the most productive age-group though with 5 wins in 11 eleven years.- Respect the market. 10 of the past 11 winners have been sent off favourite or second-favourite. Neptune Collonges and Exotic Dancer are almost sure to head the betting in 2009.- Don’t look beyond the obvious contenders on recent form; 8 winners in past decade made the three last time while the 2 exceptions fell.- The Lexus has been the key trial. 6 of the last 7 winners ran in the December 28th race over the same course-and-distance finishing:321F13. The impressive 20l winner Exotic Dancer and the faller Neptune Collonges will be the best representatives of the form. - All of the last 11 winners were previous Grade 1 winners and all bar Beef Or Salmon in 2003 had won at least two Grade 1s. In a similar vein, every winner since 1998 had won a Grade 1 chase. - Proven stamina is a must; only 2002 winner Alexander Banquet had yet to win over at least three miles in the past 11 years.- Every winner since 1998 had already won at Leopardstown while 7 could be justifiably described as course specialists having won at least thrice at the track. Neptune Collonges, who fell on his sole course run, fails this criterion.- Willie Mullins (6 wins and 3 places) and Michael Hourigan (3 wins and 2 places) have absolutely carved this race up in the last decade with only two other Irish trainers managing even a placed runner in that timeframe. However, the tide has almost certainly swung towards the English trainers for now; they had a one-two last season and raiders have won all three of our Grade 1 chases over 2m4f and further in 2008/9 with Kauto Star in the Nicholson, Noland in the John Durkan and Exotic Dancer in the Lexus.
Posted by Tony Keenan

Hennessy - Leop Feb - trends courtesy Tony Keenan

Official ratings have been a fabulous guide here. 9 of the last 11 winners here were rated at least 160 with one of the exceptions, Beef Or Salmon in 2003, yet to have been given a handicap mark; he had however won the Lexus on his most recent start achieving a Racing Post Rating of 163+.- The last 10 winners have been aged between 7 and 12 which is hardly much of a help. 9yos have won been the most productive age-group though with 5 wins in 11 eleven years.- Respect the market. 10 of the past 11 winners have been sent off favourite or second-favourite. Neptune Collonges and Exotic Dancer are almost sure to head the betting in 2009.- Don’t look beyond the obvious contenders on recent form; 8 winners in past decade made the three last time while the 2 exceptions fell.- The Lexus has been the key trial. 6 of the last 7 winners ran in the December 28th race over the same course-and-distance finishing:321F13. The impressive 20l winner Exotic Dancer and the faller Neptune Collonges will be the best representatives of the form. - All of the last 11 winners were previous Grade 1 winners and all bar Beef Or Salmon in 2003 had won at least two Grade 1s. In a similar vein, every winner since 1998 had won a Grade 1 chase. - Proven stamina is a must; only 2002 winner Alexander Banquet had yet to win over at least three miles in the past 11 years.- Every winner since 1998 had already won at Leopardstown while 7 could be justifiably described as course specialists having won at least thrice at the track. Neptune Collonges, who fell on his sole course run, fails this criterion.- Willie Mullins (6 wins and 3 places) and Michael Hourigan (3 wins and 2 places) have absolutely carved this race up in the last decade with only two other Irish trainers managing even a placed runner in that timeframe. However, the tide has almost certainly swung towards the English trainers for now; they had a one-two last season and raiders have won all three of our Grade 1 chases over 2m4f and further in 2008/9 with Kauto Star in the Nicholson, Noland in the John Durkan and Exotic Dancer in the Lexus. Posted by Tony Keenan

Deloitte Novice Hdle Leop Feb- trends courtesy Tony Keenan

Six-year-olds have dominated this race with 7 of the last 10 winners as well as 9 of the 13 placed horses. - This is one of the best races in the calendar for backing the favourite; the market leader has won 8 of the last 10 renewals.- Just 1 of the past 10 winners (Forpadydeplasterer in 2008) failed to win their most recent start.- Solerina was an atypical winner of this in 2003 as she was having her ninth run of the season; on the whole relative freshness has been important and no other recent winner had run in the previous 4 weeks. - The Future Champions Novice Hurdle has been the best trial supplying 5 of the last 9 winners. The winners finished:21111 and this year’s renewal was won by Hurricane Fly.- Graded form figures prominently among the recent winners’ profiles; all but 1 of the last 10 winners had already run in a graded novice while 7 had won one. - Proven stamina is crucial with 9 of the last 10 winners having won over at least 19 furlongs. - Respect course form as 6 of the past 9 winners had already won at Leopardstown.- There are few more consistently fruitful sources of future winners and stars than this race and it has thrown up the likes of Sackville, Native Upmanship, Hardy Eustace, Solerina and Brave Inca recently. A bet on each of the first three home on their next three outings would return 32 winners from 87 bets (37% strike-rate) for a level-stakes profit of over €14.
Posted by Tony Keenan