The Norwegian 4x4 interval

It lifted VO2max 7.2%, beating steady miles and threshold work head to head.

Who it's forAny man whose cardio is the same steady jog he's done for years.

The item

Three squares: proven in human trials. Two: a strong signal. One: early human data. Striped: the trials disagree.

Emergency: call 911.

I am not a doctor. This is not medical advice. This is self-education. Talk to a physician who has your history before you change anything.