I must say though that I have always been a proponent of specificity of training and the usefulness of on-water or on the erg strength training - you can read more here. This needs to be balanced with an athletes need for variety, and for changes in the training methods to prevent injury. Heavy load rowing without adequate preparation or experience can be a recipe for injury.
Strength Training
I just stumbled upon an interesting article on strength training for rowing you might be interested in.