: When you go up a hill your car goes into low gear because it strains the
: motor left in the higher gear.
: It becomes less efficient.

A car going up hill does not become less efficient. However, it does burn more gas per mile. It takes more energy to go up hill because the higher up the hill the car is, the more potential energy it possesses. It needs to burn gas to gain this energy. Hybrid cars use this principle in the form of regenerative breaking, so when you are going back down the other side of the hill you can capture that energy you burning going up hill.

A car may well be more efficient going up hill because they often slow down to do this. Speed means wind drag which is very inefficient. It has nothing to do with the gearing.

Likewise, going fast in a kayak is inefficient. As you go faster, the boat creates more drag, burning up energy making a wake and stirring up the water.

In this sense a paddle that causes you to go slower can be more efficient. The paddle itself is less efficient, but you waste less by having the boat move less water around.

: In paddling, the human body has to be taken in to consideration when one is
: to assume that efficiency is the least motion to move something. If I was
: challenged to move my boat the furthest forward that I could with one
: stroke, I would pick the most efficient paddle I could - probably one with
: a blade twice the size of any made.

: But if I had to use that paddle for an hour, I would probably die pretty
: quick. It would not be very efficient for me if my goal was to paddle for
: several hours. Bicycle racers always pick the lower gears to keep from
: taxing their muscles from strain. Any bicyclist who uses too high of a
: gear will tire out quickly.

The reason you would tire quickly is because the super efficient paddle is causing the boat to go faster - the boat becomes less efficient. The boat isn't going faster directly from the increased efficiency, but if you naturally paddle at 30 strokes per minute, each stroke will take you farther, thus you go faster.

If you were to ease up on your stroke rate, you would go slower. The paddle would be about as efficient as it was before, but you would be moving more slowly.

However, people tend to have a natural frequency. A rate at which they are comfortable moving their arms. It might be hard to paddle at a rate that is comfortable, in which case a paddle that slips a little more may feel more comfortable. This does not mean the paddle is more efficient, but that the body works more efficiently at a certain rate.

: The most efficient paddle is one that you can generate a strong propulsive
: force for the period of time that you would like to do that.

I would state it "the most efficient paddle-body system, is the one that can get you where you want to go while eating the fewest chocolate chip cookies."