The progressive recovery of the horse's pulse during a hold period or after a ride is one of the best indicators of whether a horse has handled the work load well. The simplest way to monitor progressive recovery is to note the horse's pulse very close to the time of arrival, at the time of presentation to the pulse takers, and then every 10 minutes or so thereafter. If within 10 to 20 minutes the pulse is in the near-resting range (mid-40s or lower) and continues to drop, the horse is handling the work well.

How to measure CRI

The Cardiac Recovery Index is a useful tool in assessing progressive recovery. The CRI is performed as follows. The horse's pulse is taken and the time is noted (for example, pulse = 64; time = 1:03:15). The horse is then trotted in hand approximately 125 feet (about 45 steps) away from a point and then turned around and trotted back.

After 60 seconds (time = 1:04:15) have passed from the initial pulse taking, the pulse is rechecked. It should be no higher than the first reading (for example, pulse 64). An accurate pulse count is imperative or the test will not be valid.

If the pulse has increased the second time it is checked, there is cause for concern. While a four beat per minute increase (60 to 64) is not overly alarming, as the increase grows so should concern. A 60 to 68 reading, for example, would be fair warning that the horse may be in enough distress that continuing the ride would be risky.

Generally speaking, if the veterinarian gets a poor CRI reading, he will ask the rider to come back again for a recheck. At that time the CRI would be repeated, and unless it had normalized, the horse would probably be pulled from the ride. The veterinarian should evaluate the horse as a whole before making his decision, but poor metabolic readings or lameness inevitably seem to accompany a poor CRI.

Like all parameters, the CRI by itself is not a set of inviolable magic numbers. The CRI does, however, give an initial set of valuable information. If the numbers are very good within 10 minutes of arrival, the horse is very likely able to continue at the same level of work. Conversely, if the numbers are clearly out of established acceptable parameters, the horse is clearly not likely to do well if it continues at the same level of exertion.

It is in these gray areas of hitting or hanging at the upper limits of acceptable numbers that one needs to go to next step. That step is to monitor recovery as shown by one or two follow-up CRIs.

Monitoring recovery

During a checkpoint, well-conditioned horses that are handling the level of metabolic stress in a good manner will reach acceptable CRI levels within 10 to 15 minutes of arrival at a checkpoint. Elite horses often reach these acceptable CRI levels within two to four minutes.

In essentially all cases, horses at checkpoints should show progressively better numbers during the course of the hold. That is to say, that a horse that has made, for example, a 64/64 recovery within perhaps 10 minutes of its arrival time should progress to, say, a 56/56 within another five to a maximum of 10 more minutes. Within another 10 minutes (by about 30 minutes from the time of arrival at the checkpoint) a full recovery to near-resting heart rates (40s) should be achievable and expected.

Another very good sign is occurring when the second heart rate is lower than the first heart rate. It indicates that the trot-out has improved circulation, heat dissipation and lactic acid build-up. So, for example, a progressive recovery check of 56/52 also provides evidence of good recovery or progressive recovery if this is a follow-up CRI.

Failure to progress

On the other hand, let us consider what a failure of progressive improvement as shown by a follow-up CRI is telling us. Let us use an example of a horse that is receiving an inspection 15 minutes after arriving at the checkpoint. Assume that its CRI was 64/68 at this time. This horse has been in long enough that if he is conditioned and metabolically fit a better CRI would have been expected. If in another 15 minutes the CRI is 60 /60 the rider should be concerned that the horse is still not yet "fit to continue" at a competitive rate.

The indication is not always that the horse may not be able to continue, but that the rider should recognize that the horse needs more rest time before continuing.

If the ride parameters are such that the horse must meet the parameters within 30 minutes of the vet inspection the rider is faced (in the above example) with a decision. Assume the horse has met the CRI parameters and all other parameters for "fit to continue." A savvy rider might well leave for the next leg of the competition, but ride more slowly and monitor carefully and even do an on-trail CRI. An even more savvy rider might check out with the timer, but not leave the stop until he/she is satisfied that the horse is eating, drinking and urinating and showing a good CRI.

A rider must also know his or her individual horse. An occasional horse might show a higher pulse and even a higher CRI when re-saddled and preparing to leave a checkpoint. Having taken a couple of CRIs spaced 10 minutes apart during the hold would allow a rider to place this changed CRI into perspective.

Conclusion

Good progressive monitoring is one of the best safety factors in the hands of the riders as well as the ride control veterinarians. To arrive at the finish with a horse that is sound and not metabolically compromised is truly to win. You will have done the best that you could with that particular horse on that particular day and on that particular trail.

Note: Dr. Kerry Ridgway is in the AERC Hall of Fame as a veterinarian and rider. He championed the "fit to continue" criteria that has become the AERC and global standard for endurance riding. He also championed the use of the CRI which longtime riders may remember as the "Ridgway trot." -Stagg Newman