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 ...

Doing the classic sit-up involves having a partner hold your feet or anchoring your feet under a brace as you lift your torso toward your thighs. This variation may be common, but it isn't necessarily ...

Beth Skwarecki is Lifehacker’s Senior Health Editor, and holds certifications as a personal trainer and weightlifting coach. She has been writing about health for over 10 years. Sprint interval ...