When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. Countdown Interval Timer is a fitness app available for Windows 10 PC and Mobile that is designed ...

Research found that doing 10-20-30 intervals can improve 5K time and VO2 max, even if you don’t go at maximum effort. Experts suggest adding this workout to your schedule one to two times per week.

High-intensity interval training has surprising benefits for fitness and physical power, but don’t stay seated the rest of the day. By Gretchen Reynolds A mere four seconds of all-out exercise, ...