Get out. No, really. Get out.
We spend way too much time indoors.
Walk, run, whatever. Just get out!
Here's what I did today. Outside the Fitness Center in the median of the parking area:
500 m run then
5 Walking Lunges (each leg)
AMRAP 20 of:
25 m Walking Lunge
25 m jog back to starting point
So go play hard!