If you've ever wondered (mid-crunch, most likely) exactly how many sit ups you should be doing every day to optimise your fitness, then you're in the right place - this is exactly the type of question ...

Hafthor "The Mountain" Björnsson has lost 121lbs and now has shredded abs. Core training is particularly important for him right now as he embarks on a boxing career. Björnsson told Insider he does ...