The WaterRower, unlike conventional indoor rowing machines, creates a non-impact and non-load bearing environment for cross-training and rehabilitation. The users weight is taken off the knees and ankles by the seated position of the exercise and the use of the unique WaterFlywheel creates an evenly loaded stroke eliminating the heavy jarring and loading experienced on conventional rowing machines, making the WaterRower a popular choice for physiotherapy and sports sciences practices around the world.
Rowing is a cyclic (or intermittent) form of propulsion such that in the quasi-steady state the motion of the system (the system comprising the rower, the oars, and the boat), is repeated regularly. In order to maintain the steady-state propulsion of the system without either accelerating or decelerating the system, the sum of all the external forces on the system, averaged over the cycle, must be zero. Thus, the average drag (retarding) force on the system must equal the average propulsion force on the system. The drag forces consist of aerodynamic drag on the superstructure of the system (components of the boat situated above the waterline), as well as the hydrodynamic drag on the submerged portion of the system. The propulsion forces are the forward reaction of the water on the oars while in the water. Note also that the oar can be used to provide a drag force (a force acting against the forward motion) when the system is brought to rest.
In sweep or sweep-oar rowing, each rower has one oar, held with both hands. This is generally done in pairs, fours, and eights. In some regions of the world, each rower in a sweep boat is referred to either as port or starboard, depending on which side of the boat the rower's oar extends to. In other regions, the port side is referred to as stroke side, and the starboard side as bow side; this applies even if the stroke oarsman is rowing on bow side and/or the bow oarsman on stroke side.