If you're planning on using this isolation time to get back into exercise, you'll need to refresh your memory.
I recently had an enforced absence from physical activity. I had eye surgery and was advised not to run, lift weights, climb or anything else to over exert myself for a minimum of 4 weeks. Now I am more than capable of being lazy when the mood takes me. I have sat on a sofa binging a Netflix show or becoming engrossed in a video game for hours (occasionally days!) on end. But I that is through choice and I always end up with cabin fever and head out the door to stretch my legs or pick up something heavy. This was different. I wasn't allowed to do anything. FOR A MONTH! I could walk, but that was it. I walked a lot. Finally, the doc said I could get back to exercising properly. So the first thing I did was go out and run some intervals. And nearly threw up. I did exactly what I advise all my clients not to do after an absence from working out. I went out too hard, too soon. My next workout, at the gym, was a much more gentle affair. Very light weights, not too many sets, taking it easy. While taking rest days is very important when you exercise, prolonged periods of inactivity lead to what's known as deconditioning (or de-training). Although it varies depending on many factors, such as age and fitness level prior to the break, as little as two weeks without exercise can cause deconditioning. Your aerobic capacity decreases (making those stairs harder to climb), muscular size and strength can drop, and your blood pressure can go up. The longer you leave it before beginning your workout routine again, the more noticeable these effects are.
But now the good news!
All that strength and cardiovascular health you lost will come back, and in all likelihood much faster than you lost it. And that is due to muscle memory. Now the name is a bit of a misnomer, we don't have brains in our limbs like the might octopus! But we have something called procedural memory, which strengthens the synapses in your brain for specific sequences of muscle movements you perform regularly. This is how a piano player is able to play without consciously thinking about the position of their fingers, or knowing how to deadlift after a few weeks of practice. Ever heard of the saying "It's like riding a bike"? Essentially, that's what it means. There is another element of muscle memory though. If you have previously gained muscle through training, it is easier to regain that muscle than put it on the first time. This is because the muscle cells gain extra nuclei during training and these can stick around for up to 15 years after the fibres have shrunk down to their previous size. Almost like the muscle "remembers" how strong it was and can get back to that level much easier this time around.
So if you do have to take an enforced break from exercise (or even an unenforced one!), don't come steaming back into it thinking you need to regain everything you lost as quick as possible. That is a recipe for disaster. You're likely to injury yourself and that means more time on the sidelines. Take those first few workouts easy. Let your body remember what it was doing gently and you'll be able to return to your former glory much sooner than you think.