Self-quarantine can be an opportunity to make the most of a sedentary day. Learn a new language online. Take up knitting. Get through that stack of books you have been meaning to read.

Or you can leave the cocoon of your couch and join the worldwide tribe of lockdown runners who are trying to adapt to the challenges of confinement.

Social distancing has forced runners to innovate, whether they are casual hobbyists releasing the pent-up steam of cabin fever or elite athletes trying to maintain their mileage.

Improvised tracks are being carved out in living rooms, and on rooftops and balconies. Indoor treadmills are getting hammered. Distances are being clocked vertically in apartment building stairwells.