On fatigue, thermoregulation and sweat

12 12 2008

Out of curiosity but against better knowing, I have been participating in a medical experiment on thermoregulation and central fatigue at BLITS, VUB‘s research institute for human physiology and sports medicine. The purpose of the experiment was to test the effect of caffeine on performance and thermoregulation (i.e. maintenance of core body temperature). My goal was to explore my ante meridian physical limits – I hardly ever wake up work out before noon.


Following a familiarization trial (a bicycle VO2max test), we, that is a ‘population’ of 8 healthy, male endurance athletes, participated in 4 climatic chamber experimental trials: 2 in 18° C and 2 in 30° C. We were given placebo or caffeine tablets before every experimental trial, which consisted of a 60 minute ‘warm-up’ at 55% of VO2 max (bo-ring!) and a 30 minute time trial at 75% of VO2 max (booyaka!). As can been seen in the graphs below, the warm temperature test was brutal while the ambient temperature test just plain uncomfortable.

Repeated blood sampling, core and surface skin temperature measurements, continuous heart rate, thermal stress and perceived exertion measurements completed the protocol, or so I thought. A battery of psychological tests (item recall, problem solving, pattern recognition) concluded the test protocol. This was not communicated beforehand and made the entire protocol laborious and time-consuming. Nevertheless, I am glad to have taken part in this experiment because:

(a) I would otherwise not push myself so hard during off-season training;
(b) I learned that warm weather all but decimates my power output;
(c) I twice reached Patrick Ewing levels of profuse sweating;
(d) I realized I have a soft spot for sports medicine; and
(e) I found the protocol (f)rigidity curiously comforting (ecological validity, who cares?)

18° C timetrial - consistently uncomfortable

30° C timetrial: consistently painful



2 responses

15 12 2008
bob rodriguez

interesting stuff. Thanks for sharing. I plan to do VO2 Max & associated testing in the next few weeks. I’ll share what I learn as things move forward. Starting to look like another ‘example of questionable decision-making” is coming … I am considering the path to biathlon/triathlon adventures. More gear: good; pool time: bad.

15 12 2008
Tom Van Hout

Try a tri, Bob. It is a fan-tas-tic sport. Humbling and flattering at the same time. You’ll expend more calories than you can consume. And remember, most sports require a ball. For triathlon, you need two. What race distance are you looking at? Drafting or non-drafting?

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