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 ...

I don't think I'm alone in saying sit-ups aren't fun. I don't know if it's because I need to have someone or something there ...

For those who live to sweat — but maybe want a chance to fully catch their breath — SIT is the new HIIT. HIIT, or high-intensity interval training, includes bursts (typically 30 seconds to a few ...