Developing a more efficient stroke
The idea here is to develop a technique that allows the athlete to transfer as much of their power output to the boat as possible. In other words, to convert as much of the athlete's energy output into kinetic energy.
The sole metric available to paddlers to gauge the rate of energy transfer to the boat is boat speed. External factors influence boat speed. These factors include water current, wind speed, water density and water temperature. Take care to ensure that boat speed is comparable between sessions when carrying out tests to develop an efficient stroke.
Method 1. Constant Power / Maximize Boat Speed
Paddle at a steady power output. Choose Functional Threshold Power (FTP) for distance paddlers or race power output for sprint paddlers. Refine technique to maximize speed, but maintain the same level of power output. This will represent a technique with greater efficiency since more of the athlete's energy output is converted into motion.
Method 2. Constant Boat Speed / Minimize Power
Paddle at constant pace (relies on ideal water and weather conditions) and try to develop a technique that minimizes your power output. This new technique has greater efficiency since it requires less energy output from the athlete in order to maintain the pace.
Moderate changes to technique will require training to develop physiological adaptation. The athlete may need to recruit muscle groups not typically used when paddling or adapt to a different range of motion.
The more efficient technique may initially feel more physically taxing. This is normal since the athlete hasn't had time to achieve fitness specific to that adaption. For this reason, it is not recommended that the athlete adopt moderate-to-major technique changes late in the season (a short period before a target race for example) as this will not immediately improve performance.