I’m sure this one goes without explanation! Unless you’re still working full time at work, you’ve no doubt acquired some new spare time. Those working from home, congratulations, you no longer have to drive to spend time driving to work!
Try getting up at your pre-isolation time and using the extra minutes in your day to get some meaningful movement in! Current recommendations sit at 30 minutes a day of moderate intensity (power-walking, light bodyweight exercise) or 15 minutes a day or high intensity exercise (running, fitness classes etc.) as a minimum. If you can’t find 15 minutes of uninterrupted time a day throughout self-isolation, you’re probably making excuses (no offense intended).