I didn't think I was weak. I'm loads stronger in my swimming/biking/running than I was last year, my weight's at a good level, and I'm feeling pretty fit.
Then I did my "Core" workout this morning.
Coach Debi has me on a core routine twice a week. Simple stuff, easy to do at home with just an exercise ball, which is cool because I hate doing weights at the gym. So for my first time, I started easy -- just 10 reps of each exercise and only one set.
Now, hours later, I'm sitting at my desk with aches in places I didn't know I had. I feel the weakness now, and I could feel it when I was doing the exercises. Weak ab muscles in particular, with a real lack of flexibility. I've got a long way to go.
The good news is that I can see the utility of the exercises and I'm going to stick with them. If I want to improve (i.e., beat people) it's what I've got to do.