Jim2's Running Page

Adjusting MP for Climatic Conditions

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I have read several race reports on the RW and RT forums from last Sunday’s NJM and there are two consistent themes among them….excellent FE and disappointment with race performance. I would like to address the latter.


One runner after another reported not making his or her goal in the race. Some blame a 10-15 mph headwind that participants had to battle for essentially half the race. Others blame the brilliant and unrelenting sun. Some complained about both. Several reports cited dehydration as a “sneaky” byproduct of wind and sun as a culprit. At least one participant even cited the very low humidity (reportedly 18%) as a contributing factor to dehydration.


However, I would like to suggest an overarching reason why so many forumites struggled in the late stages of the race and missed their goal that I haven’t seen mentioned in any of the reports….a mistake made by them before the race. Namely, failure to adjust race goals and associated pacing plans to account for the conditions. The net result was going out at a pace that was too fast paying for it later….in some cases, dearly.


Climatic conditions are beyond a runner’s control. The best one can do is deal with them. But, that doesn’t mean to just suck it up and try to force oneself to perform at the same level as if conditions were ideal. Severe climatic conditions can seldom be overcome through the “grin and bear it” approach. The way to deal with them is to accommodate them by adjusting race goals and plans. I have yet to read a NJM report in which the runner said that s/he made any pre-race changes to his/her race goal and pacing plan to account for a brilliant sun and moderately strong wind. I think that was the single biggest cause of most of the disappointment.


Just how much difference did the sun, wind and humidity make last Sunday? A convenient way to calibrate it is with a race calculator that accounts for such variables, such as the one at http://omrr.tripod.com/race_predictor.htm#form.


Headwind and sun conditions that vary from the ideal affect a race performance negatively just as a hot day does. According to the calculator referenced above and all other conditions being equal, a 10 mph headwind over 50% of the course costs a 3:30 runner 2:16, a 4:00:00 runner 3:00, and a 4:30 runner 3:23, as compared to a windless day. Even worse, a bright sun throughout the race costs the 3:30 runner 6:18, the 4:00:00 runner 7:12, and the 4:30:00 runner 8:06 as compared to a cloudy day. Combine them, which it sounds like is just about what NJM’ers experienced Sunday, and race goals and plans should be adjusted by 8:56 by the 3:30 runner, 10:12 by the 4:00:00 runner, and 11:29 by the 4:30:00 runner…..that’s a 20-30 sec/mile pace difference from an “ideal race” plan, which is more than enough to bring on problems by 15-20 miles into the race and wind up costing much more in finishing time than adjusting the race goal and plan would have cost. It is equivalent to having a realistic goal time, but going out too fast by 20-30 sec/mile….and we all know what that does to a race performance.


Incidentally, concerning the very low humidity at the NJM, the notes to the calculator point out that humidity does not affect race performance as long as the temp is below 80 degrees. That makes sense because humidity affects rate of evaporation of sweat from the skin; but it isn’t a factor in determining how much body fluids are lost in the form of sweat. In other words, high relative humidity can inhibit the cooling effect of evaporation under hot conditions. OTOH, low humidity simply ensures good evaporation but doesn’t increase the rate of loss regardless of temperature. Similarly, temp has neither a beneficial nor an adverse effect below 50 degrees. Of course, 80 degrees for a “humidity threshold” and 50 degrees for a “temperature threshold” are probably “average” numbers and can vary somewhat between individuals; but the principle should remain the same for everyone.


My guess is that most NJM’ers would have run a better, faster race with less disappointment with an adjustment to race goals and plans to account for headwind and no clouds/shade, although running the “ideal race” goal was simply not in the cards that day.


BTW, congratulations to all NJM'ers!! I was very impressed by the descriptions of the trials and tribulations you guys and gals went through because of the conditions. Take it as a learning lesson and prepare to run even better next time. And I envy you for your excellent FE!! :)