I have a client - let's call him "Jimmy J". And let's call him that primarily because I enjoy the alliteration of "Jimmy J".
Anyhow, "Jimmy J" (see how much fun it is to say that?) is actually a real person - and knows that I'm writing this using him as the example. I explained that because his question is one that I get so often (actually, quite frequently from "Jimmy J" himself) that I felt it would make a good article..
"How do I know if I'm fit?"
Actually, that's not exactly how he phrases it. More often he berates himself for failing to meet some random measure, and then asks me why he's not getting "more" fit. And when I get his email about it (for about the 1000th time) my reaction usually looks something like this:
Because you see, Jimmy J is one of the fittest guys I know. 52 years old, keeps up with (or beats) guys 20 years his junior during conditioning sessions and hockey games, does 90min trail runs with his dog on the weekends, has deadlifted over 300lbs... it's a level a 25yr old would envy.
But instead, he'll say "I don't understand why I'm not getting better. None of this should be so hard".
First of all - as I've pointed out to him (numerous times), if he didn't feel like he was working hard during a hockey game, he'd just work harder. The same goes for his trail runs, the conditioning classes, etc. In fact, to be honest, I have to constantly reign him back - remind him that if he keeps pinning the pedal to the floorboard, he'll burn out. But further to that, he seems to struggle to understand (along with many other people) that the reason it's not getting easier is because his definition of "fit" is a somewhat arbitrary and subjective moving target. Not how fast he completes a 10km run relative to the last time, or how quickly he's able to recover between shifts - it's how he "feels" during the effort.
And therein is the problem. Without a specific and tangible measure for what "being fit" means to you, you are NEVER going to know if you're getting any better.
The moral of the tale is this: if you are the type of person that wants to be able measure improvement, you have to first define what that means to you. It may be medically-based (blood work done through your family doctor, a stress test, etc), it may be strength based (how much weight you're able to move), it may be aerobically based (how fast you complete a 20km time trial on your bike) or it may be a combination of these (and more). Once you've determined what matters to you, then assess your starting point and commit to a program, doing "check-in" assessments along the way. If the numbers are improving, the program's working. If they're staying the same or declining, then it's not and it's time to re-evaluate the program (one caveat: once a person has been training for over 6 consecutive months, we're talking about a period of 12-16 weeks to remeasure, not a couple of weeks).
Otherwise - it's like going on a road trip without choosing a destination... then being upset that you don't know how far you've come or how close you are to being finished.