I regularly exercise just as I regularly work. In fact I do a manual labour so I suppose great part of my muscles are under stress routinely.
When I'm off work though I'm not the kind of sedentary people who like to indulge whatever activities spending long hours while comfortably sprawled on the couch: a spread-eagled couchpotato.
I always feel a strange unrest. I feel like I need to go outside to exercise a bit which, in my case, means go strolling for an hour or so or, as I'm going to do during summer holidays, go swimming at the beach.
I admit part of my urgency to exercise in order to stay fit is that, otherwise, just by carrying out my daily working task I would put too much stress over my body leaving my muscles a bit sore in the afterwards.
I have the advantage though that I'm never really unfit. Whatever activities I start doing which would involve cardio-vascular stress whether it might not always be a piece of cake, I hardly ever suffer too much stress.
That's why it came to my surprise reading that, within a few weeks, you can lose your cardio-vascular fitness if you stop training.
It makes sense under a physiological respect though. In the article they say that aerobic exercise linked fitness has to do with an increase in the amount of both blood and plasma circulating to raise the ability of your metabolism's cells to burn oxigen and let out energy and power.
If such stress abruptly ends why should your body continue providing blood if you no longer need it ?
Luckily indeed blood cells could be converted rapidly into some other types of cells and tissues according to newly arisen bodily necessity.
Take for instance the case that for your job requirements you need to sit long hours at the pc. Probably you put under stress hip bones and muscles, vertabrae and spine's muscles, neck and shoulders.
Then it makes sense that all blood and plasma cells convert rapidly to build newly formed cells and tissues to replace the worn out ones in the mentioned spots because they are now under continuous stress. You're kind of exercising part of your body just by sitting still at your desk , just by means of your protracted posture.
I also think that if you were an athlete in your adolescence, your body retains some memory in its metabolism that will never vanish at all. I couldn't say what the mechanism might be. However I think you never start from scratch after that intense exercise period after you give up training at all.
At least I think your heart muscle remains trained and can quickly resume accelerating its pumping under stress without taking as much as it would take with a person who never competed in sports at high levels.
As for the second article we read that assumed that by exercising lightly long hours during the day, rather than exercising heavily 30 minutes/day, you coud offset the downsides of a sedentary working routine, I'm not so sure.
I mean it could be advantageous for people who can't face running or exercising hardly such as older people. Maybe it could be good for your blood circulation either.
But I don't think you can call soft gardening an aerobic activity such as walking. Unless you are caring after an extended park.
Even sloths keeps moving even though in slow motion. But I'm afraid their blood remains at the starting blocks all along.