Fitness tests with HR/GPS systems

Fitness tests with heart rate meters and GPS systems

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The principle of fitness testing necessitates accurate measurement of velocity of the horse. Until recently this achievement has only been possible during treadmill exercise tests. New measurements based on studies of the heart rate relationship with velocity haverecently  been used successfully in field studies. Recordings are made over 5-6 gallops at least, collecting data from trotting and gallops at 600-750 m/min (16-20s/200 m) and during short sprints. These studies assist with calculation of the velocity at which the horse attains its maximal heart rate (VHRmax). The heart rate at precise submaximal gallop speeds (30-45 kph) can also be assessed. Velocity is measured with an accurate and sensitive global positioning system device carried on the horse or jockey. This technique has been used to describe changes in fitness with high speed training in two year old thoroughbreds, ⁽⁷⁾ and has been significantly correlated with racing performance in Australian ⁽⁸⁾ and Japanese studies. 

7. Vermeulen A.D. and Evans D.L (2006) Measurements of fitness in thoroughbred racehorses using field studies of heart rate and velocity with a global positioning system. Proc. 7^th Int. Conf. Equine Exercise Physiology, eds. Essén-Gustavsson, B., Barrey, E., Lekeux, P.M., Marlin, D.J.., Equine Vet. J. Suppl. 36; 113-117

8. H.L. Gramkow and D.L. Evans (2006) Correlation of race earnings with velocity at maximal heart rate during a field exercise test in Thoroughbred racehorses. Proc. 7^th Int. Conf. Equine Exercise Physiology, eds. Essén-Gustavsson, B., Barrey, E., Lekeux, P.M., Marlin, D.J.., Equine Vet. J. Suppl. 36; 118-122

VHRmax is a measurement of high speed stamina. It represents the velocity at which there is no further increase in aerobic ATP resynthesis. Increases in velocity must therefore depend on increased rate of anaerobic metabolism, and this metabolic response is quickly followed by fatigue. It has been estimated that fatigue will ensue after approximately 600-800 metres of maximal speed gallop that involves high rates of anaerobic energy output.

Recent research b y the author has confirmed that assessment of the HR response during ubmaximal gallop exercise (15-40 kph) should be measured as well as VHRmax for a complete assessment in thoroughbred racehorses. Occasionally horses with high VHRmax do not perform well, and such poor performance could be explained by poor cardiac performance at high HRs (which can exceed 225 in some horse). For example,  they could have murmurs of electrocardiographic problems could limit the cardiac output at very high HRs. Complete clinical examinations including evaluation of the EKG during exercise and cardiac ultrasound immediately after exercise can confirm such cardiac limits to performance.

In endurance horses the relationship between speed and HR can be used to guide training intensities, and evaluate future performance potential. Superior performance could be expected in horses with lower HRs during field exercise. Such lower HRs could reflect higher blood and cardiac stroke volumes, and superior economy of locomotion.

An example of simultaneous HR (top line) and velocity recording in a 3 year old thoroughbred racehorse is presented below. This horse walked at for 500 m, trotted at 18 kph for 800 m, then galloped at 38-42 kph over 3000 m. The recording was generated with a Garmin Forerunner 301 GPS system adapted for use in horses. 

Speed is recorded from changes in position every 2-3 seconds, and a heart rate is provided at each of the speed data points. Maps (stylised, or with Google Earth) show the position of the horse at each HR and speed recording, and show the course taken during the workout. Speed is given to the nearest 1 kph, and HR to the nearest 1 beat per minute. Records can be studied over time periods, or over distance. Peak speed during fast gallops is easily recorded. In thoroughbreds, this value can range from a low of 60 kph to over 70 kph in the best sprinters.

 

 

 

Regular analysis of these files can help owners/trainers address important questions.

·       Is my horse fitter than it was 2 weeks ago?

·       Have the heart rates worsened since the last recording, indicating that the horse might have an illness, or be overtraining, or not be properly recovered from its last race?

·       Is the horse training in a "zone" that is just right for the individual horse, taking into account the individuals' current fitness and maximal heart rate?

·       Am I training a horse that has a profile indicating that it has a limited rate of maximal aerobic energy output, so limiting its racetrack performance?

The individual horse’s combination of high speed stamina and sprint speed can be used to guide the type of training used, racing distances selected, and race tactics.

However, evaluation of HRs during racetrack exercise is not without potential problems in evaluation.

·       Results in all horses will be invalid in horses that “pull” during the gallop, or do not get an adequate trotting/slow gallop warm up.

·       Values will also be influenced by track conditions. Very soft and very hard conditions could decrease the measurements (meaning higher HRs during gallops).

·       Fitness values will increase in horses that lose surplus fat, even in the absence of a true change in their cardiovascular fitness. This is in the horse’s interest for best performance

·       Racing ability will be influenced by a horse’s acceleration, and 400-600 metre sprint speed, and other factors not measured by HR assessments.