This excellent question comes up frequently. It is not easy to answer as there are many factors to consider. I will approach it from two perspectives: first my morning at the Woodbine track and how the surface affects my training decisions, and second from a more general look at synthetic surfaces in the international context.

At Woodbine we are very fortunate to have two choices: the main track which is synthetic PolyTrack, and the "old fashioned" dirt track, both one mile long. There are advantages and disadvantages to both depending on weather conditions and the particular needs of individual horses. I use both tracks and am pleased to have the option.

Training decisions involve evaluation of many variables. My training day begins with a meeting with my assistant, Bob Appleton. We discuss each horse's progress; its weight, any leg or body issues, and—very importantly—how is the horse handling the surface we are currently training him/her on? Both Bob and I check each horse's legs twice every morning, first at 5:30 a.m. before I make the training decisions for the morning, and again at 10:30a.m. just before the horses are fed their lunch.

The next part of my decision-making is examination of the track. I walk out onto the track every day to see how the air temperature, quantity of rain, depth of harrow and amount of daily traffic affect the consistency, and the "going", of the track. I follow the Woodbine main track maintenance updates via twitter: @WO_TrackOps. I know when the track is cultivated, when it is power-harrowed and to what depth. I also listen to the track. Some days, when standing at the rail, you can't hear the horses gallop on the track. On other days it sounds like a dirt track‒this directly relates to the firmness of the track. A firmer or harder track makes more of an impact; a soft cushion on top causes little or no sound on impact. I pay attention to how the track looks and feels—to me in the saddle—after each type of conditioning.

The saddle is the best place from which to evaluate how a particular horse responds to the surface. When I ride a horse unsuited for the synthetic surface I can feel the "jarring". I feel the hind feet hit the ground with much more force and impact than the front. You don't have to be an expert in kinetics to feel the difference, actually it is uncomfortable for the rider and hurts my back when the horse does not travel well. I can feel when the surface hurts the horse, and I can feel when it is not galloping with ease. The same horse will gallop in a much easier way over the dirt track. It is simply a matter of the horse "handling" or not "handling" the surface. When we say "this is a turf horse" we mean that the horse uses its body more efficiently and with better performance on turf than on any other surface. The "feel" to the rider, and the race results, depend on the ease with which the horse travels on the surface and absorbs the shock of the surface. 

If, in my opinion, a particular horse is not suited to the synthetic surface I try to get it onto the freshly harrowed dirt track. The dirt track is completely perforated after being in use for 45 minutes and it does not regain good footing until refreshed with the harrow, so timing and planning is vital to get the horse onto the right surface.

The dirt track has other challenges, however, inherent with the properties of "dirt". I never use it after a lot of rain as the consistency changes completely. I would rather walk a horse in the shed row than gallop on wet dirt. On these occasions I really appreciate the work that has gone into designing a synthetic surface that manages water even slightly better than dirt does. It is one thing to stand at the rail and watch a horse gallop by splashing mud, but it is quite another to be riding that horse and feel the slips and lost footing. It is dangerous and terrifying to both horse and rider and I’d rather not put my horses or my staff or myself in that position.

Let me turn now to a more general consideration of the "synthetic vs. dirt" conversation. First, with respect to the horse, we have observed that the horse with light muscle mass relative to its skeletal frame tends to experience jarring in the high rear end: sacroiliac, pelvis, tibia, etc., whereas a well-muscled horse, once fit, seems to manage the synthetic track with more ease.

Although horses, like human athletes, can have a particular physical weakness that will cause problems irrespective of the surface on which they train, many trainers and veterinarians at Woodbine have observed an increase in injuries to the upper limbs, particularly upper hind limbs (e.g. stress fractures of the tibias, pelvis, etc.), since the installation of the synthetic surface at Woodbine. These are personal observations of a small sample group, and currently have no statistical backing. Whether this observation is strictly due to the synthetic surface, is unknown. A well-respected veterinarian with long experience at Woodbine likens the pressure taken by the tibia to that experienced by a horse with sore shins. The shin, or front of the cannon bone, becomes hot and tender, and the horse, in pain, reacts when you run your fingers gently down the affected cannon bone. The condition often affects both front legs and although the horse is uncomfortable at a gallop the rider may be unable to pinpoint the problem until it is noticed by the naked eye that the periosteum has become inflamed and very sensitive. 

Injury to the tibia, in most cases, cannot be monitored by the naked eye or by feeling the bone. Unless the rider notices an issue there is no information for the trainer to act upon. If the training program remains too hard and too fast for bone remodeling to take place, tibia stress fracture may result.

In the face of much negative publicity about synthetic track surfaces it is important to remember that they were developed for the purpose of providing a safer surface for horses and riders. We all want safer tracks—our livelihoods and the well-being of the horses entrusted to our care are on the line. The first synthetic surface was developed by Vincent O'Brien, the legendary Irish thoroughbred flat and jump trainer. O'Brien's intention was to create a surface that was consistent irrespective of the weather, hence in Ireland a synthetic or "man-made" surface is called an “All Weather”. Vincent did not have to change his training program because of the rain. He was ahead of his time.

There are two further factors to consider when evaluating the synthetic track: climate and composition.

The term "all-weather" is misleading. Ireland has a temperate climate; California is hot, and Ontario can be very cold. Synthetic track surfaces which contain oil are susceptible to extremes of temperature. Also, the composition of the track will vary from racecourse to racecourse as the components are blended from local sources. Each synthetic surface is essentially a heterogeneous mixture, defined as a mixture of two or more compounds. You may have noticed that after exposure to significant heat from the sun, the colour of the surface changes, indicating that a chemical change has taken place, and that the composition of the track is no longer what it was intended to be. 

In spite of the concerns outlined above, I still believe that the synthetic track provides a welcome alternative to training on dirt alone, which itself undergoes drastic change in extreme weather conditions. In a dry climate a well maintained dirt surface would be ideal if it could be watered a certain amount and maintenance was regular and consistent. Too much water renders a dirt track completely unsuitable for training. We are fortunate to have the choice at Woodbine.

I believe a return to the dirt track for racing would be a significant regression of the industry. There are pros and cons to both surfaces but I believe the synthetic surfaces can be further adapted by the synthetic production companies. It would be helpful if track designers were to hold conversations with individual trainers and veterinarians to discuss the effects of various surfaces on the horse’s physiology. We must work towards developing a better surface rather than regress to the dirt, that is, the "evil we know".

Following is a list of racecourses offering a synthetic track, as published in Thoroughbred Daily News:

Arlington Park Polytrack

Del Mar Polytrack

Golden Gate Tapeta Footings

Hollywood Cushion Track

Keeneland Polytrack

OBS Training Centre Safetrack

Presque Isle Downs Tapeta Footings

Turfway Park Polytrack

Woodbine Polytrack