Saturday, July 23, 2011

Slow twitch rider trapped in a fast twitch body

Mt Ascutney Hillclimb
Maybe I should have stayed home today.  My climb went as expected in one of the worst east coast heat waves ever. Regular readers know heat and I do not have a friendly relationship. Today's climb further solidified the correlation between abysmal performances and high dew points. For such a short race, here's a long, whiny, technical analysis.

I tapered for this climb. Not sure why. I knew it would be hot. I knew a PR was highly improbable. But I feel like I'm in PR climbing form right now. Three trips so far this year with tons of climbing have done wonders for my fitness.  My weight was probably the lowest ever this morning for a hillclimb race, sub-160 lbs. I've been hoovering around 160-161 for several weeks. I think it is the running. True rest days have become rare. I'm always burning calories.  And my triathlete friend says running abhors fat. It seems to tone your whole body up. I've even been doing interval workouts on hot days. My heat tolerance is probably the best ever, which doesn't say much.

My hopes were raised leaving the house this morning. It poured buckets. If the clouds hung around for a while, maybe it wouldn't heat up so fast. But with rain comes humidity. Upon reaching the mountain, the air was saturated. I bet the dew point was not much below 70F. That spelt doom for me right there.

I did a very minimalist warmup. I didn't want to elevate my body temperature. It was so muggy my glasses were fogging up at the start and I had to ditch them. I lined up with some fast guys, like Duncan Douglas and Erik Vandendries (545 Velo). I expected Duncan to beat me with a good margin. I wasn't so sure about Erik, as in 2009 we were pretty closely matched.

We were the second wave to go off. Nobody went crazy in the first 60 seconds. I stayed with Duncan and several others were just behind me. Then Duncan picks it up a bit. I let him go. At the 1mi mark, Duncan was up 30sec or so and Erik was just behind me. I think I saw 7:21 on my computer. I wanted to do better than 7:30 on first mile. Second mile is harder and should be around 30-40sec slower. I was feeling good at that point, but man, was I getting soaked. My new team kit has full length zipper, which I fully opened before the start. I could tell a full ice vest was not going to keep my core body temp in check on this one.

Erik passed me before mile two. My second mile took me about 8:37. This was very, very bad. I was already slowing down and there was nothing I could do about it. Funny thing was, I didn't really feel that bad. I was just getting slower. That is how heat stress works. It is kind of like riding into high altitude. You can't get enough oxygen to the muscles, so they just put out less power. You don't suffer any more. Actually, you suffer less than going anaerobic at sea level. With heat stress, you start slowing down long before the danger signals start popping up, like chills, nausea or confusion.

My mile three was a disaster. I think it took 9-10 minutes. It is the easiest mile by far and should go much faster than either of the first two miles. My pop-up turkey timer said I was well done. I started to doubt I'd even finish under 30 minutes. Three weeks ago when I visited Ascutney for an exploratory run, I biked up in 30 minutes right after a race-pace run, on legs tenderized by two prior days of epic mountain biking. So here I was, rested and all, just imploding. What was different? 10 degrees in dew point maybe?

I crossed the line in 29:43. If you exclude my time from last year when I raced just a few days out of a leg cast, you have to go back to 2003 to find a slower race result. Hard to get too upset about it too, as this was no surprise. Not everybody is impacted by the heat. Marti Shea crushed her own woman's record on the mountain.

People that aren't disproportionately affected by heat don't understand how frustrating this can be. Makes me want to move to Alberta or Alaska. I poked around a bit to see if there was anything new on the web about cycling economy and muscle composition. Many studies have shown that Type II muscle fiber is less efficient. It consumes more oxygen and calories per Watt produced. Studies have also shown an inverse relationship between VO2max and cycling economy. I speculate I'm a Type II guy, and I've tested with a very high VO2max. This points to being very inefficient.  I'm almost curious enough to have a muscle biopsy to prove I'm Type II, and what percentage of Type IIa and Type IIb. It could impact how I should train.

So what could this mean on Ascutney? I have to deliver about 600kJ to the rear wheel to bring myself and bike to the summit. This is independent of how fast I climb the hill for the most part.  In a PR time of about 28 minutes, this is 357W average. But my cycling economy is pretty poor, I'd say 20% at best based on UNH measurements and other bits of speculation. This means for every Watt I produce, four Watts are wasted. 4 * 357W = 1428W! That is more than a space heater or toaster oven!

As the dew point gets close to our body temperature, our body's ability to cool itself becomes greatly diminished. Another way to look at it is the maximum sustainable power becomes reduced above a certain dew point. The more wasteful an athlete is with his or her energy store, the greater the impact of heat. Climbing Ascutney at 357W in today's conditions was certainly beyond a sustainable limit for me. It had nothing to do with my threshold level or going anaerobic. It had everything to do with core body temperature.

It's a complex relationship. Your body has a lot of mass. Wasted Watts begin to elevate the temp of that thermal mass. The bigger you are, the more Joules you can dump into that mass for a given temperature rise. It is like a thermal battery that gets charged up. But the body also attempts to cool itself. You have finite surface area to evaporate sweat. If the rate at which Joules get dumped into your body exceeds the rate of cooling through evaporation, your body temp will rise out of control. This is ok for very short efforts, as your body temp may rise only 1-2 degrees and nothing will shut down. You won't need much cooling, as your body just absorbs the heat.  But if the effort is prolonged, say 30 minutes, you will eventually reach a dangerously high body temperature and things will shut down.

Quantitatively, I wasted about 2400kJ on the climb. My body mass is 72.5kg. A Joule raises a gram of water 1deg Celsius. If you assume our body is all water, 2400kJ applied to 72.5kg liquidy body will give 33.1C temperature rise if no heat is lost through sweat. This would raise my body temp to 158F by the end of the climb! You go into a comma above 105F.  So a lot is demanded by our cooling system. Slow to start sweating, not sweating enough, poor surface area to mass ratio or poor circulation at the skin can all contribute to poor heat tolerance. I have a pretty good idea I waste more energy than slow twitch riders, but I have only weak circumstantial evidence that my cooling system is weak.

When I compare my three worst hillclimbs due to heat and my PR's on those same mountains, I get a correlation of r=0.90 between delta from PR and temperature. This is extremely high, although if I looked at all the data the correlation would be weaker.  I've never had a good result on a hot day, but I have had some poor results on nice days.  In my log, words I used to describe weather for my PR's over the years are "pristine," ideal" and "cool." Temp was in the 60's at the base in all cases. My worst results used words like "oppressive" to describe the weather. Today's Ascutney climb was not my worst hot weather climb. That was Whiteface back in 2005.

Interestingly, after today's climb I felt fine, like I hadn't even exerted myself. No muscle soreness whatsoever.  I've never experienced that on Ascutney. Ascutney normally hurts me far worse than Mt Washington. I suspect this is because it is ridden much closer to VOmax, while Mt Washington is more of a threshold affair. I did take Sport Legs before today's climb. No telling if that had anything to do with it. Maybe because the heat curtailed my effort for the last half of the climb, I didn't do the normal damage.  Upon getting home, I checked my weight to make sure I was on top of hydration. I picked up 1.5 lbs from my morning measurement. Body fat was 5.6%, also indicative of full hydration.

It was still worth heading over to Ascutney. I did break last year's run/bike KOM record, just barely. Two others beat it by a lot more though. I expected Ducan to win it, but Ross Krause came out crushed Marshall's time by about 7 minutes.  I got to see a lot of people I haven't seen in a while and meet several fans in person that I've chatted with online. Probably the most remarkable point of the day was a single-legged cyclist making it to the summit. This was not a partial amputee with a prosthesis. He had no prosthesis of any kind. Truly amazing. And I whine about how hard it was to make it to the top with two good legs...


Anonymous said...

That was Jon Wilson he has the AKP Foudation(always keep pedaling foundation). He hosts a bike ride/race here in Manchester in September that goes over Rupert Mtn.

rick is! said...

holy crap. you eventually lost me while you geeked out there. glad I went into architecture and not engineering.

Len Soet said...

From a fellow slow twitch runner and cyclist trapped in a fast twitch body, thank you so much for looking into this. Unlike you, I have a very efficient cooling system and sweat lots, more than anybody I know. I can lose 6 pounds in a 1 hour run. But I have always wondered why I get so hot and my fellow runners and cyclists are barely sweating at all. Thank you for the most excellent explanation.