My body, it lies. I've known this for years, yet sometimes I still fall for it.
I went for a run on Wednesday, and even though I had previously run continuously for over a mile and a half without stopping, this time my legs were burning like crazy and I slowed to a walk after a quarter-mile. After maybe 30 seconds of walking, I started running again and continued on for well over a mile before walking again.
Wonky physiological explanation follows: your muscle cells use several different stages of chemical reaction to store energy for muscular effort. I could throw around chemical names or acronyms like ATP and ADP and phosphocreatine, but the simple version is this:
You have a tiny amount of primary fuel available in your muscle cells for immediate action at maximum output, like a hard punch or jerk.
You have a slightly larger amount of stored fuel in your cells that requires a little breaking down first. This is available for hard sustained action, like a set of heavy bench presses. Without oxygen, though, you run out quickly, like within 30 seconds or so.
You have an even larger (but still small) amount of stored fuel in your cells that can be broken down with the help of oxygen. This fuel is called glycogen and is broken down when needed via a process called fast glycolosis. But there's only enough glycogen stored in your muscles for about 2 minutes of sustained activity, at which point the muscles start having to draw on blood glucose for energy and send chemical signals to your liver to convert stored glycogen to glucose for more energy.
And during this crucial switch-over, which for me usually happens right around the quarter-mile mark, your muscles scream that they are dying. They tell you that there's nothing left, and that you need to stop so they can rest a second and get their breath back, so to speak. One of the first things you learn when running for more than a couple of minutes is to recognize that signal for what it is--a desperate lie--and push through it until your muscles get the blood glucose working.
I've known about this effect for over twenty years, and yet I still fell for it on Wednesday. Why?
Because I wasn't thinking straight is the best answer I can give. I was distracted by the fact I had overslept, so I had only eaten about an hour before running, which made me wary of pushing myself too hard. My legs felt tight and tired from the workout I'd done the night before, and I had only a limited window of time before I needed to get to work. So my mind was everywhere except on my actual running, which means that when my muscles gave their fake danger signal, I listened and walked. And immediately regretted it.
I think my fancy new digital scale lies, too. Not about my weight, even though I'm not losing much. I expect that, because when you start working out the way I have been, you build more muscle as you burn off fat. Because muscle is denser than fat, you may get heavier briefly while actually getting trimmer. I've known this for years as well.
Which is why, to keep up my motivation, I splurged a little on a more expensive digital scale that uses bio-electric impedance to determine the relative percentages of fat and muscle tissue in your body. It is not an especially accurate method, but I figured that as long as the numbers were moving in the right direction, complete accuracy wasn't as important. It would just be an extra motivational factor to know that, even if my weight wasn't going down, positive changes were still happening.
The problem is, those percentages have barely budged in four weeks. I'm getting results in my workouts (reps going up, run times getting marginally faster), and I feel as if I'm getting smaller and firmer, but the percentages on the scale are just fluctuating up and down within a very narrow range. So what was supposed to encourage me is actually discouraging me a bit.
One problem I'm having, though, is that the scale has trouble giving a reading unless I wipe the sensors first with a wet cloth to improve the connection. So I'm wondering if the (very thin) layer of water between the soles of my feet and the scale is throwing off the results at all. It shouldn't--I just barely dampen the cloth--but I'm grasping at straws wondering why the numbers aren't moving.