I was curious so I looked up the author on LinkedIn and he appears to be in his 40s. Where did you get late 20s?
>but if I felt those symptoms I'd be concerned, to
The problem is "felt those symptoms" is subjective. One person might complain because they're a little more tired after a workout than they were in their 20s, but another person might not even notice the exact same thing.
One person might be hyper aware of every little muscle spasm and twinge of pain, another person might just ignore it.
There's actually a fair bit of evidence that depression can make people experience normal muscle contractions used to move food through your GI tract as pain. Doesn't mean it's not real pain to the person involved, but it does make non specific belly pain very unhelpful for doctors trying to diagnose underlying medical issues.
Is the average person in such bad health that they believe you're heading downhill in your late twenties??? In most sports this is peak athleticism.
I'm in my mid forties, and obviously I'm slowing down, but if I felt those symptoms I'd be concerned, too.