Thanks to Charles J for writing with some very interesting ideas about my report of the onset of lower power output in the Death Valley Double at the ~130 mile mark. My thoughts follow each idea.
In general, I think Charles is on the right track— the body is a precision mechanism, and it could be a combination of factors that steadily degrade its ability to sustain an effort. Perhaps not any singly factor, quite possibly several factors that together degrade the body’s overall ability to sustain power output. After all, 3 hours was a long ride for me when I was in my 30’s.
I should also say that while I was a little lacking in energy the next day for riding, the following day I enjoyed a strong 2-hour bike ride— not fully recovered, but mostly so. So I don’t think I stressed my body beyond any difficult limit.
I am curious to see if I experience the same fatigue pattern in the March 24 Solvang Spring Double.
OK - I'll take a crack at how many possible things could have robbed you of power after the 130 mile mark.
Adrenal hormones - cortisol. There is a daily fluctuation of cortisol levels. They peak in the morning and then go down in the late afternoon. There are a lot of other circadian issues which make a constant power output over a large part of the day difficult. Your body can get used to having a peak performance at the same time of day each day - even if it is not at the same time cortisol levels are highest. But extreme endurance events are so long that I am certain you will have to go through a bad part of your circadian rhythm.
DIGLLOYD: I am sure this could be a factor, but once I am “humming” I just tend to keep going steadily. I ride at different times of day during training, usually 2-3 hours, so that time spans a good chunk of the day. Worth being on the lookout for this effect. I do notice that in early afternoon it can be a bit harder to get out and get started, but this quickly passes once on the bike.
Adrenal hormones - adrenalin. It is possible that all the mechanical issues robbed you of stores of this vital hormone. Each time your water bottle cage rattled, you got a tiny fight or flight response and late in the day when you really could have used some more of that, you were all tapped out. Another issue with managing this is the influence of caffeine (which stimulates production of adrenalin). If you are a morning caffeine person, then it will wear off after a while. Your own body isn't always good about picking up the slack. If you aren't a morning caffeine person, then caffeine can really offer a boost when you start to lag. But if you have spent all your adrenalin already then the caffeine is less effective.
DIGLLOYD: Possible, but I stayed pretty calm the whole time, except perhaps for the great fun of riding fast for the first 6-7 hours. I am not a coffee person, so I had no big breakfast burst of caffeine, only a little from some Perpetuem.
Beginning at hour 3, I was scarfing Perpetuem Solids Espresso flavor, which have caffeine. But I could not eat nearly as many approaching the 140 mile mark, and I had lost my appetite.
Hypoglycemia - The symptoms suggest this as the brain needs either glucose or ketones for fuel. There is some interesting stuff coming out about the fact that you don't actually have to consume calories to get a metabolic boost. Just placing flavors on the tongue can begin the process of mobilizing energy. I know, I sound like an ad for one of those 5ml energy boosters but it makes sense. When you eat, the body knows more energy will be available soon - thus it allows current energy stores to be more easily utilized. But the downside for athletes is that eating will send blood to the digestive tract. The nose and the tongue are really where digestion begins and they send a lot of signals to the brain, which has a lot of control over this process. My favorite saying in French is "L'appetit vient en mangeant" (the appetite begins when you eat). Some people apply that principle to expensive camera equipment as well as food.
Hypothermia - You would know if this was happening. But if you were getting cold, then you would start to hold on to more blood in your core and less would circulate to the big muscles for propulsion. Overheating also robs power - in that case blood will circulate to the skin for cooling and it won't be available for oxygen delivery to the muscles.
DIGLLOYD: Great quote!
I was taking in enough calories up to the 135-mile mark, so that I’m sure that blood sugar had to be reasonable— nowhere near a bonk. But that does not mean I had the same muscle glycogen supply in my system as the first 8 hours, and I could have miscalculated. Indeed, perhaps I had exhausted all muscle and liver supplies of glycogen, and thus food was the only significant source. The relatively hard effort of the first 5 hours might have drawn down my glycogen stores too far.
Definitely not hypothermia, as it was ~68° F by mile 140, very pleasant, not too hot and not too cold. And I had stripped off clothing by mile 100 from warmer temps.
Hyponatremia - this is a known complication of very long endurance events. The "suffering" stimulates the production of ADH which will cause your body to hang on to water better than it hangs on to sodium - especially if you hydrate with relatively low concentration fluids (which all of them are). The brain is the target of all effects - so your symptoms are consistent with this also. The only way to really manage this is to slowly get behind on water replacement so that you can keep the salt and water in balance. You tried this - but may have been hyponatremic when you started. Obviously this strategy has a bad end point also.
DIGLLOYD: This is an interesting area. I started out very well hydrated (maybe too well hydrated). I also consumed a full 2 liters of fluid in the first 2 hours or so (3 gallons over the full day), and had to urinate 5 or 6 times in the first 4 hours— too much. I had little need to urinate starting at mile 150 or so.
However, had I been sub-par in “balance” I can’t possibly see how the high power output could have lasted so many hours.
I did take Hammer Endurolytes starting at hour 3 and consumed about 20 of them for the remainder of the day (along with a total for the day of 3 gallons of water). I ran out around mile 170 of all supplements.
Boredom - boredom is induced by a lack of stimuli to the senses. Hard to know if this is the case. I suspect there is little variation in smells or sounds in Death Valley. If the road is like the one in the picture where the road is a straight line with a never changing view of the mountains, then that could do it. Maybe it should be called "Bored to Death Valley"?
DIGLLOYD: I do not get bored riding. I absolutely rule this out. I know myself, and this is not possible. Besides, I was having great satisfaction in passing rider after rider until mile 130 or so— maybe too much fun, maybe I was riding too hard. But it felt easy.
Nutrient lack - This seems unlikely but extreme efforts are the ones that could unmask a magnesium deficiency, carnitine deficiency or some other obscure vitamin, or mineral or unclassified nutrient. A lot of athletes in these extreme events use supplements. Personally I am not a big fan of them.
So I would conclude that there are a lot of things that can happen - the common theme is that they have little to do with your actual athletic ability or even your training. The people who can successfully manage all these issues are not necessarily the most fit athletes. In addition, training to be able manage these issues might not be particularly healthy. I would classify these events as survival tests rather than athletic contests.
DIGLLOYD: A Double Century is extreme, I agree.
For supplements, I took Hammer Aminos (2 per hour), Hammer Anti-Fatigue Caps (1 per hour) and Hammer Endurolytes (2-3 per hour)— reasonable amounts I think.
I would tend to agree that some kind of nutrient or fueling issue could accumulate. The issue is figuring out what it is and how to address it. For the Solvang Spring Double, I will have another data point, to see if a similar ~135 mile change occurs.
Disclaimer: An ominous cause of this is undetected heart disease. We all have heard about highly fit individuals that drop dead or have a cardiac event. A lot of time in retrospect they do note a warning sign. Often there is some physical task, that they can no longer do and in retrospect there just is not a good explanation. Since they could still do more than almost everyone they knew, they usually ignored this.
DIGLLOYD: I observed other riders. Everyone was slowing down the last 50 miles from what I could see. Even guys drafting each other were pulling only 5-10 watts more than me riding solo. I do not think my experience was unique, and my heart rate charts looks perfectly consistent with power output with no signs of a higher or lower output relative to power produced.
All my ECG tests show a very strong, very regular heartbeat. I have one each year as part of my annual physical. I have also had some discussions with a cardiac surgeon (reader of this site!) as to what happens with a highly trained heart in terms of beat regularity.