Resting and Recovery Heart Rate With advancements in the latest technology, the horse heart rate monitor is now starting to replace the stethoscope in many stables, studs, farms and veterinary clinics. The latest heart rate monitors are accurate and reliable, provide a quick reading (within 10 seconds) and are simple to use. They eliminate ‘human error’ that can occur with ‘counting the heart beats for 15 seconds’. In particular, the latest hand held Polar VetCheck heart rate monitor provides a quick and easy method to measure your horse’s resting and recovery heart rate. But why would you want to measure resting and recovery heart rate? What vital information can they give you about the condition and health of your horse? Resting Heart Rate Resting heart rate is the heart rate when your horse is resting quietly in a stall, stable, paddock or pasture. Typically, a horse’s resting heart rate is usually in the range of 25 to 40 beats per minute. Measuring resting heart rate in relaxed, resting conditions is important because sudden excitement, fear, or anticipation of exercise can elevate the heart rate rapidly to over 100 beats per minute. Resting heart rate is one of those ‘vital signs’ that can provide an excellent benchmark when it comes to assessing the general health status of the horse and how it is recovering between training sessions, competitions and races. It is important the trainer treats each horse as an individual and establishes a usual or normal value for it. If the resting heart rate is 6-10 beats per minute higher than normal, a ‘vital sign’ has changed which provides some evidence of stress. The stress may be the result of a hard training session the previous day, an injury that is not yet apparent or an impending infectious disease (cold) or noninfectious problem such as colic. Whilst an increase in resting heart rate does not necessarily mean the horse should not be exercised on that day, it would be wise for the horse to be further examined before making a final decision – check all the legs, take the rectal temperature and note the horse’s attitude and willingness to train. How to measure resting heart rate In order to make sense out of your horse’s resting heart rate, you need a reference level with which to compare it. This benchmark is best achieved by measuring the horses resting heart rate over 5 consecutive days and taking the average of these 5 measurements. For example, if a horse’s resting heart rates were 27, 26, 29, 30 and 27 beats per minute for 5 consecutive days, then a good reference level would be 27 + 26 + 29 + 30 + 27 = 139/5 = 28 beats per minute. In this case, any resting heart rate greater than 34 bpm (e.g., 6 bpm higher than normal) would alert the trainer to some evidence of stress. However, before constructing this reference level, it is important to ensure that your horse: ü Is in a healthy state ü Is free of pain and injury ü Will have fairly easy training sessions during the 5 days you are taking the measurements ü Is used to having the heart rate monitor put against its coat It is important to develop a pattern or routine where the measurements are taken under similar conditions (i.e., before feeding, exercising or saddling). Remember, you want to compare ‘apples with apples’ so standardization is extremely important. Once you have established this reference level for your horse, you can start to measure resting heart rate on a daily basis. Make sure you record the resting heart rate along side the previous day’s training notes and any of your subjective observations. Another ‘resting heart rate’ used by some owners and trainers is ‘saddled and ready to work’ heart rate. In general this heart rate seems to fall between 36 to 48 bpm but also needs to be determined for each individual horse. As with the normal resting heart rate, an elevated ‘saddled heart rate’ may indicate impending disease, pain or psychological stress. A careful evaluation should be made before making a decision as to whether to continue the training session. Recovery Heart Rate When a horse stops exercising, its heart rate starts to drop quickly. This ‘recovery heart rate’ is generally very rapid in the first 60-90 seconds after which it decreases more gradually towards normal resting values. Figure 1 shows the recovery heart rate of a horse after completing a 2000 m interval at a rate of 14.7 s per furlong. At the end of the interval the horse’s heart rate was 203 bpm; by 90 seconds it had dropped to 111 bpm. The measurement of recovery heart rate can provide the trainer and / or owner with a fitness index throughout the training program and help detect possible soreness or lameness and help assess how the horse has handled or is handling the actual training session. Fitness Index In humans, resting heart rate decreases considerably as a result of endurance training, with highly trained athletes often having resting heart rates of 35 bpm or less. Whilst it has been suggested that horses show a similar trend, equine research generally supports the fact that the resting heart rate of a horse does not decrease after a phase of training. Therefore, when it comes to monitoring changes in fitness, it is best to use heart rate measurements during and after training sessions (recovery heart rate). An example of how recovery heart rate changes with training is given in Figure 2. This graph depicts the differences in recovery heart rates of a horse after participating in a training program. In general, a horse recovers faster when it is fitter. Recovery heart rate is accepted universally as a means to assess the ability of endurance horses to continue during competitions. It is suggested that in the fittest horses, recovery heart rate drops below 70 bpm within 5-10 minutes of stopping exercise. Horses that do not recover to a heart rate below 70 bpm within an hour are likely to have received too much stress and require medical treatment. Recovery heart rate in the veterinary checks is usually 64 bpm. Injury or Illness An abnormally delayed recovery heart rate in the horse compared to what is considered normal, should alert the trainer and / or owner to the possibility of illness, lameness or overtraining. It is important to understand that recovery heart rate is sensitive to environmental factors (heat, humidity), excitement, fear, anticipation of exercise and unfamiliar surroundings. For example, hot, humid weather is associated with a higher exercise heart rate and a slower recovery heart rate. Horses training at the racetrack often become excited when completing faster work and having other horses working around them. This often results in recovery heart rates remaining ‘elevated’as depicted in Figure 2. How to measure recovery heart rate A simple way to assess recovery heart rate is to record the heart rate after a set time period on stopping exercise. Whilst this time period will vary from stable to stable, a 5 or 10 minute post exercise reading probably gives the most useful information. Remember, you are comparing this heart rate to what you consider ‘normal’ for each individual horse. As with resting heart rate, use a standardized procedure when monitoring recovery heart rates and take into consideration any ‘outside’factors which maybe affecting it. Combination of resting and recovery heart rate A popular method used by many endurance riders and veterinaria ns in evaluating a horse’s fitness is the Cardiac Recovery Index (CRI) test. The test involves measuring the heart rate at rest, exercising the horse, and then rechecking the heart rate at a predetermined time after the start of exercise. This test is often used within 10 minutes of rest after exercise. So how is this test conducted? CRI Protocol Ø Measure out a course of approximately 80 m in total length (40 m out, 40 m back) Ø Measure and record the horse’s ‘resting heart rate’ Ø Briskly trott the horse, in hand, the 80 m distance. Start timing at the beginning of the trott and measure the heart rate again after 1 minute. It takes most horses 25 to 30 s to cover the 80 m distance, allowing about a 30 s recovery time before measuring the ‘recovery heart rate’. Gait inspection is also conducted during the trott. Ø Because the ‘recovery heart rate’ is taken at a set time after the start of the trott (1 minute), the test has a built in compensation for speed: horses that trott quickly have a longer recovery period before the heart rate is taken and visa versa. Ø The criterion used to determine whether the horse is fit to continue is that the ‘recovery heart rate’ is no higher than the ‘resting heart rate’. Figure 3 depicts the heart response of a horse undertaking the CRI test. Interpretation of the CRI It is suggested that within 10 or fewer minutes of rest after exercise, a fit and healthy horse should be able to pass the CRI test. The following criteria are often used in decision making as to whether the horse should continue in the competition: Ø Recovery heart rate equal to or lower than resting heart rate: horse is fit to continue. Ø Recovery heart rate 4 bpm higher than resting heart rate: horse not fully recovered – no major concern but repeat test after an additional 5 minutes of rest. Ø Recovery heart rate 8 bpm higher than resting heart rate: horse not fully recovered – some concern that the horse has not fully recovered. Take measures to reduce stress (e.g., cooling, rehydrate) or cease the competition or workout. Ø A horse that does not pass the CRI test within 30 minutes of rest should not continue to exercise or compete and should be carefully monitored. Summary A technological aid like the heart rate monitor should always be regarded as an adjunct to, and not a substitute for the horseman’s ‘gut feel’. However, the heart rate monitor can now provide accurate and quick readings on one of the horse’s most ‘vital signs’ – resting and recovery heart rate. A change in this ‘vital sign’ from its normal value may indicate a health or injury problem with your horse and can help you determine whether to stop training and / or seek professional veterinary care. Knowledge of your horse’s expected resting and recovery heart rates can help you detect a serious problem early in its development, providing you with better stable management and giving your veterinarian a greater chance of successfully treating the problem. Just as importantly, information about the response of the ‘vital sign’ can help you and your veterinarian monitor the horse’s response to treatment. Key Points Ø With the new Polar VetCheck heart rate monitor, owners and trainers now have a quick and accurate method to measure their horse’s resting and recovery heart rate. They now have a way to communicate with th eir horse. Ø The horse heart rate monitor is an essential owner’s / trainer’s tool for the safe, effective and professional management of their horses. Ø Changes in a horse’s ‘vital sign’ of resting and recovery heart rate may indicate impending problems such as overtraining, sickness, injury or psychological stress. Ø Initially, you need to establish what is an expected normal resting and / or recovery heart rate. This needs to be established under standardized conditions. Future readings need to be measured under similar conditions. Ø Keep a record of these values for day-to-day reference and decision making.