News from Delco Road Running Club

Use your head when exercising in the heat. That is the overt message of a series of recent studies showing that cooling the neck before exercise in hot, humid conditions can improve athletic performance. But the research also raises this provocative issue: Even if you can exercise harder in the heat, is it really a good idea to do so?

The experiments in question began several years ago, when researchers at Roehampton University in London found that healthy young men could cover significantly more distance during a timed run on treadmills in a hot laboratory if they supplemented their workout gear with an ice-cold strap-on neck collar. The collar, lined with flexible artificial-ice packs, noticeably lowered the skin temperature on the men's necks. But the collars did not lower their body temperatures over all. So how and why, wondered the researchers, did starting an exercise session with a cool neck - not a body part normally associated with running ability - affect the men's performance?

To find out, they recruited a new batch of volunteers and had them run in a humid laboratory heated to a stifling 87 degrees. This time, they ran until they were exhausted, much longer than in the initial trial. (I leave the olfactory conditions in that enclosed space to your imagination.) The results, published this year in The Journal of Athletic Training, showed that the volunteers ran farther when they wore the collars, and when their legs finally gave out, their core temperatures were significantly higher.

It is widely accepted in sports science that while an elevated core body temperature can be dangerous, leading to heatstroke and worse if it gets too high, it is simultaneously protective during exercise in the heat. It seems to be the signal that tells the brain to shut down the muscles before disaster occurs. In study after study, when the core body temperature of someone who is exercising nears a critical point, usually above 104 degrees, that person's ability to continue abruptly ends. You feel absolutely exhausted and stop, before heatstroke sets in. (Sometimes this fail-safe function doesn't work, obviously, since people do develop heat illness, but the incidence is highest in sports like football, where players are often expected, if not required, to continue exercising no matter how they feel.)

In this experiment, even though the runners' bodies grew warmer when they wore the collars, their minds weren't registering that fact, and they reported feeling no hotter than without the collars. Cooling the neck, the authors concluded, had allowed the runners to continue exercising as their core temperatures rose, improving their time to exhaustion "by dampening the perceived levels of thermal strain."

Just how the collars had achieved that neat trick couldn't be determined by this particular experiment, said Christopher James Tyler, a lecturer in sport and exercise physiology at Roehampton University and lead author of the study. But, he continued, it is likely that the collars cooled the blood in the neck's carotid artery, which then flowed to the brain to produce a "subsequent lowering of cerebral temperature" and convince the brain that the body was cooler than it really was.

But is subverting your brain wise? Should those of us who will be running, cycling or otherwise exercising outside in the coming months buy a cooling collar - available on the Internet and at many sporting goods stores - or create a D.I.Y. version by freezing a bandanna or towel and draping it around our shoulders before we head outside?

The answer, as is so often the case in sports medicine, depends on your exercise goals. "I don't think everyday recreational athletes should be worrying too much about performance" in the heat, said Douglas Casa, a professor of kinesiology at the University of Connecticut and an expert on heat illness. We should instead "concentrate on staying healthy," he continued, beginning with acclimating slowly to soaring temperatures over the course of a week or so. (You can find a wealth of information about acclimating and otherwise avoiding heat illness at the Web site of the University of Connecticut's estimable new Korey Stringer Institute, which was founded by the widow of Mr. Stringer, a football player, after his death from heatstroke.)

If, however, you are fit, competitive and ferociously intent on outdoing your training partners, then, said Dr. Tyler, the data suggest that "the use of a cooling collar can improve performance and capacity." But he continued, "The user needs to be aware that this could lead to overexertion" if your brain disastrously misreads your body. Check your heart rate throughout the exercise session, he advised. Runners' heart rates were not affected by cold necks during his experiments; they rose as would be expected. So, he said, if you find that while wearing a collar, "you're exercising at 15 beats per minute more than normal, you might want to slow down."

Accept, too, that a collar is likely to have at least one additional drawback. To be effective, Dr. Tyler said, it must be quite frigid to start with, and that cold slap to the neck has been known to cause an ice-cream headache.