Tower running - the latest painful craze in getting fit
This sounds horrible to me, but I can't imagine anything else being better for your legs to be honest.
It has become so popular that races are held in some of the world's most iconic buildings including the Empire State Building, the Sears Tower in Chicago and the planet's high skyscraper, Taipei 101.
The Taiwanese building has 2,046 steps and was completed by Italian Marco De Gasperi in 10 minutes and 29 seconds.
The world's longest stairway is in Switzerland at Niesen Treppenlauf in Mulenen Niesenbahn and has 11,674 steps.
Training is simple. On towerrunning.com, the guidance simply says: "Find stairs - then climb 'em (sic). Should you not be able to find stairs - then please substitute with a very steep hill."
Tower running is so tough that even elite athletes used to running long distances struggle.
Austrian Andrea Mayr, who holds her country's record for the women's 3,000 metre steeplechase, has won the Empire States "Run Up" twice, as well as the Taipei 101.