Vikings might be best known for looting, pillaging, and awesomely horned headpieces, but these guys also knew a thing or two about rowing.
Rowing is one of the best full-body exercises out there. Each stroke works the back, legs, shoulders, and arms concentrically to initiate the movement, while the hip flexors and abs work eccentrically to decelerate trunk extension at the end.
This challenge involves four sets of rowing, with each set doubling the distance of the previous one. You should think of each set as a mini-race, requiring a maximal, all-out, full-Viking effort to complete.
Rest periods between sets should be equal to the amount of time it took to complete the set. So if it takes you 1:53 seconds to complete 500M in set 3, your rest period before set 4 would be 1:53 seconds. As the sprints increase in duration, so do the rest periods.