Hot or Not

The Fat Cat was going to ride alone Tuesday. That would’ve been the smart thing to do. But, he heeded the summons of Big Daddy and Aerobinator. Now, Legs, he got the same call. Being far wiser than The Cat, he had the good sense to decline. Thus, it was left to the Cat to save his faster companions from the dire depths of heat stress to which they surely would have exposed themselves in his absence. Of course, this meant plunging himself into a furnace of critical core temperature and complete failure. Hey, anything for a friend, eh.

Riding up Beulah and into the highlands of Preston County, WV in the mid-day heat lead to the now typical response from the Cat’s deconditioned frame. He gasped for air, the cranks seemed to seize up, sweat induced weather systems formed about him, Jesus and a parade of other deities shimmered and danced out from his dehydrated brain— blah, blah, blah. You’ve read it all before. Suffice it to say that the Cat had it hard and his companions had to wait a lot.

Big Daddy Birdman insists that it is not deconditioning or weight gain that has caused the Cat’s fall. He is sure that the heat is the culprit. In as much as The Cat could talk, and it was not much, conversation turned to how heat affects physical performance.

One point had to do with the blood. A truck drivin’, perpetual part time student, genetic cycling monstrosity friend of ours once told big daddy that heat induced performance loss had to do with the blood. The theory is that when it is hot, a greater proportion of blood is shunted from the core to the extremities for temperature regulation and thus is not available for the transport of oxygen and nutrients to the muscles. However, in 1979, a scientist called Nadel published a study showing that blood flow was, in fact, not limiting during exercise in hot conditions. This was followed by studies in the 1990's from Denmark which showed the same thing - there may be a challenge to blood supply during exercise in the heat, but the body is more than capable of meeting it in healthy individuals. And so, that theory was disproven.

Just before The Fat Cat started to loose the power of speech again as another grade kicked up on Nicholson, it was suggested that there may be heat related changes in oxygen binding capacity. It is true that increases in temperature affect the oxyhemoglobin curve. Heat causes hemoglobin molecules to let loose their oxygen molecules easier and would actually improve tissue oxygenation. But, the effect is not that great and, in reality, the actual body temperature is kept in a fairly narrow range and does not usually elevate more than one or two degrees in the absence of heat exhaustion/stroke. Also, the oxyhemaglobin curve is strongly affected by ph. Increased acidity equals better release of oxygen. It has been shown that there is an increase in muscle glycolosis with increased temperatures. This in turn results in increased levels of lactic acid which would decrease ph and, you guessed it, result in better release of oxygen to the muscles. So, that shoots the whole heat/ oxygen theory right in the ass.

Between wheezes, The Cat muttered something about the brain actually limiting work output and sending out pain messages and the like so as to maintain the tight thermoregulatory range. Turns out, this is probably the chief factor in heat related performance deficits. Exercise in heat causes central fatigue. That is, increasing body temperature affects brain function and the drive to exercise. With strong motivation, you might be able to get the body temperature up to 41 degrees celsius, but beyond that, it seems that exercise is very nearly impossible. Remember also that heat stroke happens at a temperature of 42 degrees. In normal individuals, the brain stops you from getting yourself into trouble. This information was derived From EMG and EEG (muscle and brain tests). Here is some stuff I lifted for you geeks if you want a little more info.

1. At very high (40 degrees) body temperatures, immediately after the athletes had become exhausted, they found that the activation of muscle by the brain was actually LOWER than when the body temperature was only 38 degrees. The graph below shows the EMG activity in the quadriceps muscles after exercise in the hot and cool conditions. It's quite clear that the EMG, which is a measure of activation of muscle, is lower when the body is hot. So that gives an indication of why the cyclists were no longer able to push out the required force - their brain simply prevented them from activating the required amount of muscle.

There was supposed to be a cool graph here but the site won't take it. Sorry.
2. There was evidence of reduced arousal/motivation levels once the body temperature rose. In fact, what was found is that there was a very good correlation between a rise in body temperature and a reduction in arousal. Motivation or arousal, incidentally, was measured using EEG and the ratio of certain brain waves which are known to indicate this parameter. The key point here is that as the body temperature gets higher, the motivation declines, and this in turn is responsible for a rise in the perception of effort. They therefore found a good correlation between RPE and a rise in body temperature, though of course, correlations are often a slightly misleading. The key is: Increased body temperature = decreased motivation/arousal = increased effort perception.

After The Cat beat out Aerobinator for second at the county line sprint, the power of logical thought left him. Talk of optimum human performance ceased. Pure survival kicked in. He hung far back from his fellow Grimpeurs and was barely able to hold onto the handlebars.

Despite his ignominious defeat in the sprint, Aerobinator proved himself (contrary to popular belief) to be one hell of a nice guy. On the run down rt. 7, he dropped back and offered The Fat Cat a fat wheel to suck on. The Benevolent One gently tugged the Fat One up to Birdman and kept him there. Thanks.
As soon as The Grimpeurs parted on their separate paths home, The Cat collapsed in the first roadside clearing he could find. He lay there for fifteen minutes swallowing Swedish fish like a drunken frat boy and seriously contemplating drinking water out of a dirty stream. Ah yes, good times…good times.