This super hard, super-effective style of training isn’t just the “it” workout ... 120 percent VO2 max that can last from 10 to 60 seconds with equal recovery periods; and sprint intervals ...

“VO2 max is a measure ... when needed. Sprint at a pace you can sustain for 10 to 15 seconds, then jog for the remainder of the minute. Repeat for 20 minutes. Work up to sprinting for 20 or 30 seconds ...

“In general, VO2 max work should be completed at about 90 to 100 percent of your max heart rate,” says Benson. That’s about ...