Released by Concept2 (the same company that invented the popular Concept2 Rower, or Erg) in 2009, the SkiErg emulates the double-pole technique used by Nordic skiers. The user stands in front of the towerlike machine and grabs a handle in each hand. Then he uses his full body to pull the “poles” down before butterflying his arms back up to smoothly transition into another rep. The result is an upper-body-heavy cardio sesh that’s easy on the joints and, according to Equinox trainer Dan Daly, C.S.C.S., promotes postural health.