How many years you've been exercising is directly proportional to your ability to improve your fitness, here's why...
Your training age is how many years you've been doing a particular activity. It can get in the way if you don't keep it in mind.
To be clear, if you've been running for four years your training age is four. That'll be true regardless of your actual age.
If you've been working out at the gym for three years and running for 2 months, then your gym training age is three. But your running training age is 2 months.
That's important because of expectation. You've going to the gym for three years. So starting a running program will be easy, right?
No. Your three gym years don't qualify you to start an intensive running programme. Or intensive cycling/triathlon training plan - or whatever.
You need to build up your capability in each form of exercise - and make no assumptions.
The other thing to watch out for is when your actual age means you are going to struggle to improve your fitness.
It's a fact that as you get older, it gets harder to improve your fitness.
That doesn't mean you should stop trying. It means things are going to get tougher. You might have been able to run for miles when you were younger. There's zero guarantee that you'll be able to once you are in your forties and fifties (or more).
So, if you've let your fitness slide and and now want to fix it, you have three things working against you:
Okay, I'm joking with that last one (perhaps).
The point is: it's a case of putting the work in, but keeping a realistic expectation on what you can achieve.
Time for a story...
A couple of years ago I was a keen runner. I ran almost every day and I ran for miles and miles.
I decided I wanted to do an ultra marathon. A 24-hour race where you kept going for as long as your body would let you for the 24 hours.
I trained by running mile after mile, pushing my body to the limit and beyond.
The event started on Saturday morning. By the Saturday afternoon I knew I was an idiot. By the time I was 30-40 miles in, I definitely knew I was an idiot.
By Sunday morning, the soles of my feet were hanging off (heavy, persistent rain = wet feet) and I couldn't feel my legs.
I ended up covering over 60 miles.
The problem was: I believed I could do it. I trained under assumption that I could do it. I took part in the event thinking I could do it.
My training age was 2.5.
Bugger. Too young for that kind of long distance running.
And I was in my early fifties in actual years. I hadn't allowed for how broken I was going to be at 2am on the Sunday morning, after almost 14 hours of constant running.
The best advice is this: be mindful of your training age and actual age when trying to build your fitness. That way, you'll avoid injury and chunks of your feet falling off.