How to analyse the locomotor profile of a racehorse?

In order to analyse and determine the locomotor profile of a racehorse, it is necessary to focus on the stride length and pace of the horse’s strides.

The first indicator, the stride length, corresponds to the length of the strides at trot and canter. The stride length increases with the speed of the horse.

A horse’s stride frequency is the second essential indicator for understanding the locomotor profile. This corresponds to the number of strides the horse makes in one second and varies according to speed.

These two data vary most of the time to the detriment of each other.  It is noticeable that when a horse extends his strides, it is immediately more complicated for it to maintain a high stride frequency. Similarly, when a horse speeds up his stride, it immediately becomes more difficult for him to maintain long strides. Furthermore, the pace is in most cases correlated with the horse’s endurance: a high pace is difficult to sustain over a long period of time and will therefore hinder high endurance.

The various types of locomotive profile

Although all horses are different and each has his own style of gait, two typical profiles of racehorses can be distinguished:

         Sprinters: Sprinters are horses that develop their best over short distances. In order to reach high speeds quickly, so-called “sprinters” will develop a very sustained stride frequency (more than 2.45 strides per second). However, this very high stride frequency is not sustainable for the horse over a long distance.

         Milers & stayers: These are horses that run over longer distances. In general, milers run for distances of 1600m and more while stayers run for 2400m and more. These longer-distance races require a very high level of endurance which is characterized by great stride length and a fairly low stride frequency.

TROT: 

In harness trotting or mounted trotting races, the “trotters” adopt a symmetrical gait. Each limb performs the same movement, both in terms of distance covered and the time taken to cover that distance. The average of trotters monitored by EQUIMETRE shows a stride frequency of 2.3 strides per second with a stride length of 5.94m.

The range of the trotters is limited. Indeed, during an instant, when the horse no longer touches the ground, the hind leg which is moving forward risks touching the front leg which is moving backwards. To compensate for this physiological constraint, the hind legs move forward from the outside to limit this interaction.

GALOP:

Unlike the trot, the gallop is an asymmetrical gait. Depending on whether the horse is galloping on the right or left side, the order in which its limbs are placed varies. On average, the data collected by EQUIMETRE show an average stride frequency of 2.43 strides per second and a stride length of 6.85m per stride.

In the same way, the breathing rhythm of racehorses varies according to the pace they adopt and the speed they deploy.

TROT:

At trot, the breathing cycle is independent of the movement of the strides. Trotters adapt their breathing to their needs during the race. Thus, during the so-called soft phases of the race, those which are less intense, the horse can save himself by reducing his breathing rhythm. As the race and the effort intensifies, the horse will greatly increase its oxygen supply by considerably increasing his breathing rhythm.

GALOP:

Conversely, at a gallop the breathing is adjusted to the horse’s stride rhythm.  The horse breathes in while suspended and breathes out when his limbs are laid down.

This coordination between the two is mechanically carried out and does not vary according to the speed or the tiredness of the horse. Therefore, when a horse needs to increase his heart rate, the horse is forced to increase its pace.

Recommended distance

Depending on the locomotor profile of each horse, the entry distance and the race strategy differ. For a horse with a large stride length, it may be appropriate to start the sprint from a distance in order to allow the horse to reach his maximum speed by giving it time to increase the size of his strides to their maximum.

However, if the horse’s pace is very high, it is preferable to wait until the last moment, as the maximum speed will be reached quickly and a sprint starting from a distance may exhaust the horse, which will then no longer be able to maintain his pace in the last few metres. Therefore, a high stride length is not “better” than a high pace, it is rather a question of making the best use of each horse’s strong points.

The impact of slopes :  

On ascending slopes, the effort required of the horse is much greater. Indeed, the stride length decreases sharply due to the additional force required to cover the same distance as on the flat. If the horse expends the same amount of energy, its stride frequency will be less on uphill than on the flat. The pace also decreases.

Conversely, on downhill slopes, the horse’s balance must be maintained and during the race he puts a lot of weight on the front of its body.

The impact of the terrain :

The grass tracks on which racehorses run most of the time are very dependent on the weather. Temperature as well as rainfall affect the quality of the terrain.

Synthetic tracks are relatively independent of the weather, although slight variations do exist. On the other hand, their quality is far from equal to that of natural tracks.

 The type of ground on which the horse moves influences not only his speed but also his locomotion. At a constant speed, the harder the ground, the longer the strides will be and, on the contrary, the deeper the ground, the shorter the stride.

Speed and locomotion

To reach a certain speed, the horse takes strides of a certain length and duration. A horse’s pace increases linearly with speed until he reaches maximum speed. The pace varies in the same way if it is necessary to go from 25 to 30km/hour as it does if it is necessary to go from 55 to 60km/hour.

Unlike the stride frequency, the stride length does not change linearly. Its evolution is more important at low speed than at high speed. Thus, at full speed the variation of the rate will produce greater acceleration.

During the races, the horses constantly adapt their locomotion to adapt to the many changes in pace due to the terrain, the racing train or the jockey’s will. The horse adapts by first modulating his pace, then its strides to reach the pace-stride length pair for which he is most comfortable at that speed.