Updated: Oct 2, 2019
There is an old saying that if you read something enough you will end up believing it. Well in the example of horses 'action' it is almost certainly the case.
Many years ago I kept hearing about the 'knee action' of a horse and being statistically minded I wondered if it was a variable I could exploit and add those already used in my modelling. I went about building a database of horse conformation/skeletal structure/physical action and a few other related variables. After several years the sample size was large enough and any variance had settled down. The results were not what I had expected and it became an obsession to find out why.
I started tracking horses from foal to yearling, to breeze ups, to the track. Conformation wise there are plenty of pointers to what a horse will want at the track and they are extremely valuable in lightly raced horses. But it's the actual 'action' that seems to confuse people the most people, including very good and experienced journalists.
In basic terms the consensus is a 'high knee action' means a horse wants soft ground and a 'low grass cutting action' means the horse would prefer fast ground. The theory being that a horse whose front feet (hooves) land down harder can bounce out of the ground quicker, whilst the faster lower action means they can skip along the harder ground. This theory is widely recognised in the industry as being correct but that is because there is no factual evidence to support this and indeed it is not exactly true!
I will use the example of a fantastic (now retired) stallion Dansili, because he is possibly the best example. He has a ground dependency and a massive sample size, dating back to his first runners in 1999. He has incredibly good statistics on fast ground and pretty moderate ones on slow ground (his A/E reads as follows - Firm 1.2, Gd-Fm 1.06, Good 1.01, Good-Sft 0.82, Soft 0.86 and Heavy 0.56).
This is a classic statistical example of a fast ground sire and we are led to believe that his offspring have a fast stretching, low cutting action. The only thing is, this is not true. His offspring have predominantly (over 60%) a high knee action. Dansili is not the only one where the stats simply do not tally up with the myth, in fact the evidence clearly shows the knee action theory is only the fourth most important variable when assessing ground for a horse.
So let's look at other factors that could be the cause for a horse to prefer one ground over the other. From data available the main three that do effect the horse's favoured going are
1 - Hoof size. It is fairly obvious that larger feet cover larger area and therefore harder to skip on fast and easier not to sink in soft and vice versa but as obvious as it sounds I have never heard a commentator refer to this in the parade ring (or sales ring by any agent for that matter) which is astonishing considering how influential it is on a horses ability to go through the ground. Simply look at the hooves of an Acclamation/Exceed And Excel compared to Sixties Icon/Authorized. You will be amazed at what you see, even to the untrained eye it becomes very obvious very quickly.
2 - Front pasterns - Again it makes perfect sense and the data backs it up. A pastern (the part of the leg between the fetlock, the bottom of the cannon bone and the top of the hoof) can vary greatly in angle and length from horse to horse and is often passed down from the sire or dam sire (although remember these are big sample sizes and does NOT apply to every horse). In short (although this is more complex than the hooves) the bigger the angle the closer the fetlock goes to the ground when weight bearing and the more likely the horse will be able to tackle softer ground but slower on faster ground. Horses with a more upright pastern prefer faster ground. The sample size on this data is so big it is extremely compelling. Dragon Pulse/Sixties Icon/Fast Company are good examples, (but smaller in sample size than others you may no longer see at the race track) where you may see the 'slacker' pasterns on flat bred horses and Dalakhani/Sir Prancealot tend to be good for studying those more upright.
3 - Rear action This part is critical but is much harder to see on an untrained eye. The reason is that it is actually the back legs that provide the power to the horse, not the front, but we are a generation who have become obsessed with the front knee action and it is once again something you rarely hear mentioned in racing circles. This is bizarre considering it is the natural way of assessing a horse's power. Unlike the media most trainers are very competent at detecting a horse's rear muscular and skeletal strengths when they stand. Gaskins, hocks and the hip etc are all very important but for a punter it is the action of that leg that is important when watching it race. I won't go into too much detail as this article would end up a larger version of 'War And Peace' but to give you examples I would analyse the rear action of a few Scat Daddy/War Front offspring and straight away after Pivotal/Motivator and hopefully you can see one has a 'long slamming action', the other more a 'pendulum action'.
This action is not to be confused with the difference between a sprinter or stayer, another reason it is harder to detect.
Remember this does not mean every sire/dam sires will look/run this way but in large sample sizes most will. Also the three critical bullet points above ALL need to be examined carefully and thoroughly on each horse, you cannot simply assume a Dragon Pulse won't go on firm ground OR a Dalakhani on soft, you need to know all of the above to be sure, to a fair degree of certainty at least !