Movement: Catch, drive, finish, recovery. Initiate the rowing stroke with the legs, followed by the torso, finishing with the arms. Bring the handle to the bottom of the chest on each stroke. On the recovery of the stroke the arms should come forward first, followed by the torso followed by the legs. Start the knee bend and leg recovery only after the handle has past the knees. Be sure to generate as much range of motion in the legs as you can, while avoiding excessive flexion in the trunk.
Caution: If you have a history of flexion-intolerance in your back (and you are not a professional rower), the row is a poor choice and you should swap this exercise for an extension-based conditioning exercise like swimming.
Instructions and effects for the Rowing exercise 
Movement in Sagittal and Frontal Planes