I don’t want to say that it was a bad weekend, but I made at least two dumb-assed triathlon mistakes and wound up with my first—albeit minor—injury of the season. Argh. As I noted later that afternoon, I got up early for Spin Class on Saturday, but despite having plenty of time, I still managed to walk out of the house without my Gatorade bottle, resulting in a near blood-sugar meltdown in the middle of class. Then when I headed out for a five-mile run yesterday morning, I pulled a muscle in my left calf. Dumb!
Let’s take Saturday’s mistake first. It was much less complicated.
A human body always burns a mix of blood sugar (glucose) and fat for fuel. This is true for everyone, all the time. Fat is by far the more plentiful fuel supply, even for folks who’re very skinny, and when we’re at rest or working at a relatively low heart rate, fat is what we’re burning most. However, our brains run exclusively on glucose, and more to the point, glucose is the easier, more “high octane” fuel. So as we increase our effort level, our metabolism naturally shifts on a sliding scale—from burning primarily fat with a hint of glucose to burning primarily glucose with a hint of fat. This is why you may sometimes hear that walking is a better exercise for losing weight than is running. Not because you burn more calories walking—you definitely do not—but because your body will burn fat as a fuel source when you walk, and because you can keep walking for a lot longer than you can run.
As a triathlete—or any other kind of endurance athlete, for that matter—the trick is to train your body to burn fat more efficiently while simultaneously taking on nutrition mid-effort to prevent your blood glucose level from bottoming out. There’s a lot to that, of course, and doing it well is not at all easy, but bottom line, you want to be able to go at a pace that you can sustain over the length of a given race, and you want to be burn blood glucose at about the same rate that you can replace it. For efforts that are less than forty-five minutes and accomplished at something like a comfortable aerobic pace, this is generally not a big deal. However, once you start going longer and/or harder than that, you need to start thinking about fuel. This is one of the big reasons why folks use Gatorade or other sports drinks during athletic activity. Sports drinks have simple sugars, sugars that your body can absorb easily during exercise, allowing you to partially replace the glucose you burn while racing or otherwise working out.
The rest is simple math. One hour of Spin Class with repeated intervals of very hard effort plus pure water instead of sugary sports drink equals low blood sugar. I mean, I didn’t bonk—I didn’t run completely out of blood glucose and hit “the wall”—but I did suffer, and my performance in class declined unnecessarily. I also had to cancel the second half of my planned workout.
What happened Sunday is a little harder to pin down.
Having not run on Saturday because of low blood sugar, I got up early Sunday morning. I planned a simple five-mile run, and I planned to take it easy. With the early wake-up, I had time to eat a little and do plenty of stretching and yoga, and so although I’ve been tired lately, I had absolutely no reason to think that anything was going to go wrong. With that said, fatigue has been an issue for me lately, and the pulled calf muscle, sustained somewhere around the second mile of what would turn out to be a roughly three-and-a-half-mile run in total, is almost certainly my body’s way of telling me to back off or face far more serious consequences.
I noodled over this for awhile, and basically, here’s what I think: although I’ve been working no harder this year than last year in terms of total aerobic effort, the fact that I’ve not been swimming at all means that I’ve put far more work on my legs than ever before. I’ve not been riding too much, and I don’t think I’ve been running too much, but I’ve been doing both together quite a bit, and given the intensity of the Spin Classes on top of everything else, well, something’s got to give. As it happens, that something was my left calf.
|My training log from February 2011. Note all the swim yardage.|
|This season has had roughly the same total aerobic work but NO swimming.|
The difference, I think, explains my recent fatigue and this injury.
So. At this point, the short term fix is rest. That’s easy. Long term, however, is a little trickier. Yes, I probably need to add in some swimming for balance, but beyond that, I also think I need to look closely at my workout intensity. Which is to say that you can add mileage, or you can up the ante in your workouts, but if you do both at the same time, bad things generally happen. Well, I’ve done both, and I should’ve known what was coming. Mileage is fine, but I obviously need to add more steady-state, base pace aerobic mileage before I worry about getting faster. And I know that, but I got excited by the early season rush.
What can I say? These things happen. However, as an experienced triathlete and soon-to-be triathlon coach, I need to stop them from happening quite so often to me.