As climbers we all value flexibility and core strength …. so check this out … In the 1940’s a trio called the Ross Sisters performed staggering feats of strength and contortionism. If you don’t fancy close harmony singing in the style of the Andrews Sisters jump straight to 1.52. If this is all genuine … and as far as I can see there’s no reason to suspect it isn’t, the moves at 2.50 virtually defy physics as well as being utterly terrifying.