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Cool Out!

Cool Out!

Cool Out!

071

While suffering under a bright sun, on the white sand, by the turquoise-green waters of the Caribbean Sea a couple of months ago, I managed to plow my way through the #1 best-seller, Seabiscuit. Actually, it was no chore at all, this true story being one of the best-written, most fascinating books I have read in a long time, due in large part to the depth and breadth of the factual details on horses, jockeys, and thoroughbred racing.

One of the more interesting details facts discussed in the book concerns the practice of “cooling down” thoroughbred horses immediately after a race. As author Laura Hillendbrand describes it:

For horses, “downshifting” from strenuous exercise is risky. If they are brought to idleness too soon after running all-out … their major muscle groups can seize up in an agonizing spasm called “tying up.” In addition, they can develop colic, a potentially fatal digestive crisis. Because of this, horses must be brought down from exercise gradually, slowly decelerating over about a half mile after a race and then undergoing a long walk.

Reading this reminded me of another old saw in the lexicon of running wisdoms: the “cool-down.” In some ways, it is the bookend of that other fondly-held chestnut, the pre-run stretching routine. Of course, just a few issues ago (Article #67), we saw that there is very little evidence to support the belief that stretching prevents injury or improves performance. Could it be that the same is true of the alleged benefits of the “cool-down?”

A review of the available scientific literature unfortunately fails to turn up much direct evidence to either support or contradict a clear relationship between the cool-down and decreased incidence of injury. In the one study I found that explored this question (Am J Sports Med. 1993 Sep-Oct;21(5):711-9

), 421 male runners were divided into two groups, with one performing a standardized warm-up, cool-down, and stretching routine, while the second group did none of these . (Since the intervention group did not limit the exercises solely to the cool-down, the results cannot be attached to that activity alone, so there would be no way of knowing for sure if this is what played the primary role in answering the question of its effect on injury prevention. In any case, the results of the study are not encouraging.) At the end of the 16 week study period, there were 23 injuries in the control group, while there were 26 in the intervention group, so clearly this routine was not effective in reducing the incidence of injury.

Other studies have examined factors, such as lactic acid removal rates and muscle glycogen resynthesis, which could reasonably be extrapolated to address the question of improving performance. The supposed benefit of accelerating the removal of lactic acid from muscles after intense exercise is the most common reason given for the advisability of cooling down after an event or workout. The build up of lactic acid is blamed for that feeling of soreness or heaviness in the legs that every runner knows all too well. Sore muscles are associated with poor performance, so the reasoning goes that anything that helps to remove the source of that soreness will improve subsequent performance.

While there is some controversy over whether lactic acid is, in fact, the primary cause of next-day muscle soreness – inflammation and swelling caused by micro-tearing of muscle fibers is the other leading suspect – several studies have been done over the past 25 years to investigate the effects of a cool-down on the removal of blood lactate. The results indicate that light, active exercise after intense, exhaustive exercise is more effective than complete rest in reducing lactic acid levels in muscles (J Appl Physiol. 1994 Oct;77(4):1890-5; J Appl Physiol. 1975 Dec;39(6):932-6). While this may be seen as a positive support for the practice of cooling down, more direct evidence that this improves performance is still lacking.

Another area of interest to researchers investigating performance improvement is the resynthesis, or recovery, of muscle glycogen after a workout or race. Glycogen is the basic fuel used by muscles during exercise, particularly aerobic forms of exercise such as distance running. It stands to reason that the more quickly and completely this fuel source is replenished to the muscles after exercise, the better subsequent performance will be.

Studies on the effect of cool-down exercise with respect to glycogen replenishment show somewhat conflicting results. At least one study (Med Sci Sports Exerc. 1994 Aug;26(8):992-6) indicates that passive recovery (rest) is the better choice, while another (Am J Physiol. 1987 Sep;253(3 Pt 1):E305-11) shows no difference between rest and cool-down. The weakness of both studies, however, is that the glycogen replenishment was measured 60-90 minutes after exercise, so the results are only meaningful to those athletes who would be looking to perform at a high level again within that time frame. Most runners are more concerned with how they will feel the next day, but this has not been measured in any of the studies I have found.

The bottom line is … who knows?. The value of the “cool-down” in terms of injury prevention is largely unknown, and for performance enhancement the best evidence is at least not really negative. I don’t think there is enough good evidence either way to state unequivocally that you should or shouldn’t cool-down after running. In a case such as this, I say go with what feels best for you.

At the very least, I’m pretty sure you won’t become colicky if you sit or lie down after a race.