horse heart rates


heart rates and horse fitness testing.

Horse fitness testing is conducted, using heart rate analysis to identify horses with inferior, average and superior stamina.


rationale.

Stamina (“staying” ability) is a major part of success in middle and longer distance races. When combined with information on a horse’s 400-600 m speed, the training and racing strategies can be matched to a horse’s individual physiological strength/s. For example, there is little value trying horses over longer distances if they have inferior stamina. Results are also used to evaluate horses with poor racing performance. Early identification of inferior stamina can assist racing and other management strategies.


methods

1 - in the field.

HRs and speeds are recorded over several days at trot, canter and gallops. Results from several days of records are analysed.Advice on ideal HR and GPS systems provided

2 - on a treadmill.

Heart rates are recorded repeatedly during 5 minutes of trotting, one minute walk, and then 2 minutes of slow gallop. Ideally a 15-20 second fast gallop is added to measure maximal HR. A “heart Index” score is provided. Average heart index is 100, with a range of approximately 75-125.
Equine R.

use of results.

Horses with low heart index have poor stamina and cannot be expected to race well over distances beyond 1200 m. Racetrack and treadmill training can be modified to improve stamina. A scientific training protocol can be individually designed for each horse to efficiently and safely improve stamina. Horses with very low heart index may have health problems that require veterinary diagnosis and treatment.


heart rate during exercise. 

There is a linear relationship between heart rate and speed of submaximal exercise. This pattern is common to all horses during exercise. However, the actual heart rates that any horse records at the trot or slow canter can vary greatly, depending on age, fitness and health of the horse. The heart rate during slow work can also be elevated in horses with lameness or other problems.

For all horses there is a work speed which does not result in an increase in heart rate. A plateau occurs, and no further increases in heart rate occur, regardless of increases in speed. The highest heart rate that can be recorded in such a test is called the maximum heart rate (HRmax). Maximum heart rates in horses are generally in the range 195–240 bpm. Each horse has its own individual HRmax.

During swimming, heart rates may be as high as 180–200 bpm when horses are forced to swim at higher intensites. However, heart rates as low as 120–130 bpm have also been recorded. Effects of swim training have been demonstrated.

Heart rates at onset of trot and canter exercise can be erratic, taking 4-5 minutes to achieve a steady rate. This may reflect excitement, or can be related to a physiological phenomenon in horses whereby the heart rate increases quickly at the start of exercise, and then decreases after this initial ‘overshoot’ to a lower rate over the next few minutes. Rapid changes in blood volume may also contribute to HR instability at onset of exercise.

At the start of fast exercise, the increase in heart rate is very rapid. Within 30 s, the heart rate can be greater than 200 bpm. The rate of increase in heart rate at the commencement of exercise depends on the use of a “warm-up” period.

After exercise, heart rates decrease rapidly in the first minute, and then continue to decline at a slower rate. Results of several studies demonstrate that recovery heart rates are lower after a standard exercise test as a result of training. The results can be easily influenced by excitement and the activity of the horse during recovery, and unless the exercise is carefully controlled on a treadmill, differences in intensity of exercise performed will make the results very difficult to interpret. Lack of standardisation of the horse’s activity both during exercise and during the recovery period makes useful interpretation of recovery heart rates very difficult.

Post-race heart rates can be used as a guide to inadequate recovery, as heart rates which remain elevated post-exercise are a warning sign. Veterinarians who are requested to check horses that may have performed poorly in races should routinely check the heart rate and rhythm. Heart rates which remain >130 bpm for 5–10 min after exercise suggest a poor recovery. Such a result could indicate that the horse is not fit enough, or that the horse may have clinical problems, such as atrial fibrillation, respiratory infection or lameness.

There is a predictable effect of training on heart rate during slow exercise, but little change in either maximal heart rate or resting heart rate. During submaximal exercise heart rate may decrease by 20–30 bpm, but responses to training vary greatly in different horses.

Several other factors can influence heart rate during submaximal exercise. If the horse developed lameness, muscle soreness, respiratory infection or another illness, the heart rates at the same speed could increase. Likewise, if the horse stopped training, the loss of fitness during detraining would be reflected in a higher heart rate during slow speed exercise.