The maximum heart rate (or HR Max) is the maximum number of beats per minute that a horse can reach during exercise or training. This maximum heart rate is personal to each horse.
It decreases slightly with the age of the horse and is little influenced by training. Moreover, it is not correlated with the performance level of a horse. In the same race, it was shown that the maximum recorded heart rate of horses ranged from 204 to 241 BPM (Evans, 2007).
The maximum heart rate is personal to each horse.
In order to better understand the work of your horse, both work and heart rate ranges, it is necessary to assess the maximum heart rate at least twice during the season.
How to measure the maximal heart rate of each horse?
The maximum heart rate can be measured during an exercise where the intensity of the exercise will require a large energy input. Typically, a 70% to 80% maximum speed effort for at least 1600m or on a track with a positive elevation gain, or a force greater than 90% of the maximum speed for 600m.
However, in order to assess the speed at which the horse reaches its maximum heart rate, the incremental test will stop the effort when the maximum heart rate is reached and not push the horse unnecessarily. This test also makes it possible to evaluate the speed at the maximum heart rate.
Horses reaching their maximal heart rate
The maximum oxygen volume (VO2 max) that a horse can use is one of the best indicators of the level of performance. In addition, the heart rate is strongly correlated to the volume of oxygen consumed by the body.
Once the HR Max is reached, there is very little left for the horse to accelerate and reach its VO2 max. This means that it has to tap into its other sources of energy to be able to accelerate.
However, as the other energy sources are limited in quantity when racing, a horse can hold its maximum speed for about 600 to 800 meters…
Effort zones are generally defined in terms of HRmax, as follows:
- Up to 70% of the HRmax: the body uses fat as its main mean of production.
- Between 70 and 80% of HRmax: fat continues to be consumed but the difference is made up by glycogen. The body is still able to supply enough oxygen to eliminate lactic acid. We can talk about alactic anaeroby.
- 80% to 90% of the FCmax: from this threshold the body starts to accumulate lactic acid. The more lactic acid it accumulates, the less effective muscle contraction is. This threshold is associated with a speed called MAV (Maximum Aerobic Velocity) which is the maximum speed that can be reached without producing lactic acid. Above this threshold, the body enters the lactic anaerobic phase.
- At 90% to 100% of the FCmax: the body accumulates a lot of lactic acids. It becomes painful for the muscles and the body to support the exercise.
Example of HR zones analysis from the EQUIMETRE platform