Urban legend has it that Bill Koch roller-skied up Mt. Greylock pulling his school-age daughter on a mountain bike. A rope around his waist, Koch supposedly double-poled eight miles straight uphill with a seventy-pound child behind him. Was this an extreme new strength-training concept, a fulfillment of childcare duties, or both? Even if the story isn’t true, it illustrates the lengths some parents will go to get a workout. TIME The number one limiting factor...
