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 ...

HIIT, or high-intensity interval training, is increasingly popular, and it provides plenty of benefits, from torching calories to increasing your VO2 max and overall athletic performance. SIT, or ...

Sprint interval training, or SIT, is super trendy right now. It’s a great way to improve your running speed and to get in a hard interval workout, and I’ll explain exactly how. But I also need to ...