Kam and I are both injured, so we’ve lost both the enthusiasm for some of our hikes and the will to drive long distances. This, combined with my insomnia, means some late starts on hot San Diego hikes. So, this hike seemed like the perfect time to experiment with food and water intake.
Two weekends ago, we did the same hike from Lake Poway, which is 2-3 miles shorter (call it 7.5 miles) relatively early in the morning. I did that hike without food or water and felt great; actually, better than usual.
The hike from Blue Sky is almost exactly 10.5 miles round-trip to the peak. We started at 10:30 am or thereabouts when it was already above 80 in the parking lot. I took no food or water just to see how it went. And it went amusingly.
To make sure we started off well hydrated and chock-full of glycogen, we drank wine the night before and had caramel corn for dinner at the movies, along with very little water. Thus, our bodies were already nice in shock before we even started.
The hike started off well enough. It was hot and dry, and we sweat a lot. I felt fine until the picnic tables that are roughly 2.1 miles from the peak. I started feeling hot and breathing harder than I should be. That was a little more than an hour in under the bright sun, so I figured it was the initial signs of mild dehydration and my usual early bonking (I just don’t do well without carbs when I hike / run).
Things slowly degraded from there. I had to rest a few times on the way up, which was unusual, but Kam was very patient. We made the peak in exactly two hours, but I felt worked and my legs were oddly tired, as in shaky and weak, as if I’d done a much harder workout. I figure that was the low blood sugar more than actual fatigue, but my balance was also slightly off so we rested a few in the peak in a nice light breeze.
We fast-hiked down to the lake junction easily enough, and while it was hot, it was still pleasant enough even if all the little uphills were taking their toll on me. The traverse around the lake and down to Blue Sky is where I could feel the body starting to run down a bit more; I was breathing heavily even on the downhill, but it was still just more of an effort. There was no nausea or lightheadedness.
It’s about a mile from the (closed) bathrooms in Blue Sky to the trailhead, and that’s about where I really started to feel the lack of food. I didn’t really feel dehydrated (I was still sweating and felt hot, but not too hot, and my heart rate came down quickly when we rested), but I just had no energy in the legs. At 0.5 miles left, I started having to rest even on relatively flat ground.
At 0.2 miles to go, I was worked and slightly nauseated. There is a tiny little uphill at the end and I was dreading it. Sure enough, I had to rest twice just getting up that tiny hill and was nauseated all the way back to the car.
So, somewhere in there I should have learned something. I figure 90 min or so without food or water is fine, maybe 75 min in hot / dry weather. Maybe 120 min if properly hydrated, fed and rested beforehand. But after that, things fall apart quickly. Some of that could be training, but I suspect that my rate of sweat loss and carb-hungry muscles are not really made for low-cal / low-water endurance in the heat. I was truly worked when we got home.
My net water loss, taking into account what I drank in the car on the way home, was more than 10 lbs / 3 liters. I suspect what’s more important was salt and mineral loss, which is harder to estimate. And of course Kam was fine b/c she actually ate and drank like normal person — even though her net loss in water was almost the same (just 1 lb less), which is interesting.
Next, I need to figure out the minimum salt / water / carb intake required to stave off the bonk / dehydration for 4/5/6+ hour efforts. Let the experiments begin!