Stephen Dooley: I was wondering if you might help with a question I have struggled with. Last year I replaced my weights program with low SPM, maximum drag ergs. I have been asked to let the coach know for comparison what this might be in Kg/m. I know my stroke length and have been told by various people that water pressure is about 40kg and that erg drag of 145 is about equivalent to this. Do you have any idea what a drag of 220 on the erg is equivalent to in terms of lifting a weight.I would also mention that this specificity of training moved me from the lower half of our squad to the top four in the space of a year!Terry O'Neill: You cannot compare the loading of a rowing stroke with the loading of weights. If you lift a free weight of 40kg it is 40kg throughout the lift, this is called isotonic. A rowing stroke is zero load at the catch then rises to a maximum and decays back to zero. The load on a rowing stroke is dynamic in that it will depend on the acceleration and length of the stroke. It may reach 40kg at its peak but 20kg is closer to the average load throughout the stroke.The rowing machine feels like rowing and not like weight lifting because the load varies in the same way as the load varies in a rowing boat. The resistance is created by the friction of the fluid medium you are accelerating through. Water and air are both fluids and therefore perform in the same way. The Performance Monitor measures the speed, acceleration and deceleration of the flywheel to calculate the power applied. The drag factor number refers to the constant air flow through the flywheel, which is controlled by the position of the damper lever. Some people say that a drag factor of 135 feels like a coxless pair and a drag of 220 feels like a tub four. You can compare the feel of the machine to a boat but you cannot compare either to free weights.