Canoe and kayak stroke are almost identical except the upper paddle blade is sawn off and you return on the same side rather than alternating sides every stroke.
You have to start by thinking of the paddle stroke force as the sum of a linked sequence of movements, just like a baseball pitch, ie. wind up, step, weight transfer, torso twist, arm adduction, arm rotation, elbow extension, wrist snap. One thing out of sequence, and the ball is only as fast as from the broken link to the end. In paddling, the sequence is hyper-rotation and reach forward, followed by blade drop, same leg drive, hip rotation, and torso rotation, all with bottom are straight (you could have a string tied from shoulder to lower shaft and it would serve the same purpose,) followed by slight elbow bend and chicken wing as the blade comes out between you knees and hip, and you rotate back forward as far as you can go.
Upper arm stays pretty locked in a bent position for maximum leverage. The only reason your top hand moves forward is because you are rotating around the axis of your spine. As your pulling shoulder moves back, your up shoulder moves forward. Your shoulder/upper arm keep the same locked angle, your albow keeps the same angle, and shoulder, elbow and wrist should all be at shoulder/chin level until the blade comes outof the water. Only then does your top arm dip slightly as your top wrist twists the blade to parallel the water as you reach forward again. Notice what happens if you punch with your top hand:
(a) you lose all your leverage
(b) your stroke is shortened by 8-12" per stroke, and
(c) your paddle and blade angle change, so you are now lifting water up and pulling the boat down rather than pulling the boat forward and up.
Leg drive every stroke! Your leg push really initiates each stroke. No push and you lose all the power of your legs and hips, even if you're getting good rotation otherwise. A good paddler looks like a cyclist with tiny peddles.
4. Hyperextend or hyper-rotate forward every stroke. I called this the coiled spring effect. Try sitting on the floor in paddle position. Twist to a place you can comfortably hold for 20-30 seconds. Now super exagerate it to a place that's really uncomfortable and you can't hold it for more than a few seconds. That's the place you want to be at the front of every stoke. It also is stored potential energy that combines with the kinetic energy of your muscular rotation when you uncoil.. The person beside you should be able to read something on your chest or your back. In the boat, try to touch your toes every stroke without leaning forward. I used to have a coach that would have us duct tape a broom straw to the deck on each side (sticking out over the water) and we had to hit it every stroke.
5. Pause at the front of the stroke, not the back. If you watch an expert paddle on frame by frame video, you will see a slight pause or hesitation at the front of each stroke, in that hyper-extended place. That is the set-up and the rest, so that the power can be applied maximally and efficiently. As the rotation pauses while hyper-rotated, the blade extends into the water, allowing maximum purchase when the paddler starts the leg drive. Many paddlers make the mistake of no pause (hummingbird), or they pause at the back end of their stroke. Back end pauses slow the boat down tremendously. Your stroke should be dynamic and accelerate out of the water so that you can pause up front as the boat continues to glide. No pause not only makes you more tired, but most adherants lose the front 8" of their stroke becasue they did not set up. Try doing a hesitation drill where you count to 3 bannanas at the front of every stroke, and then take a perfect, powerful stroke.
6. Focus on the front of the stroke. Have you ever tried lawn mowers (also called one arm rows) with a really heavy dumbell like 80 or 100 pounds? Have you noticed that down at the bottom you can pull it easily, but the higher you lift it, the hearder it gets? That's because the muscles used at the bottom(front) are much stronger than the muscles used at the top(back) of the pull. We are much stronger in the first 18 inches(feet to knees) of our stroke than in the back(knees to hip) and we have almost no pulling strength past the hip. So why not spend your time and effort in the effective zone and minimize time in the ineffective zone? Too many paddlers bring the paddle way to far back. If you think about accelerating it out at your knees, it will come out at your hip, which is just about right.
7. Watch that bottom elbow. It should be almost straight almost all of the time. If it is bending as you pull, you're using your bicep to pull which is a lot weaker than your legs and back. Remeber your pull is only as trong as your weakest link.
8. Make sure you are not bobbing or lunging. Every lunge changes the wetted surface and slows the boat down. All you power comes from rotation.
9. Make sure you are pulling straight back with your pulling shoulder, not making a big sweep or arc. Any motion off centerline is pushing your boat sideways and diminishing your forward speed.
10. Perfect practice results in perfect technique. Your body is always neurologically learning good technique or bad technique. Whenever your technique starts to fade, back off your pace until you're back in the groove, then increase your speed again. Never practice intervals or sprints where your technique goes out the window and you flail. That only reinforces bad technique. Biomechanical studies have shown that even the most efficient paddlers in the world only utilize about 12% of their effort output, even less than the internal combustion engine! For those of us lesser mortals, that should indicate just how important flawless technique really is. Most paddlers can make far greater gains by imporoving their technique than they can with years of strenuous physical training. Just recently I helped a lady paddler take over 2 minutes off her 500 meter time. Thats over 40%, and she did it in less than a month.
11. Have a spouse or friend video tape you from every angle, do this every other week if you can.
12. I am convinced most injuries such as bursitis or tendonitis in paddle sports is a function of inefficient technique. Proper ergonomics uses the most powerfull muscles and does so in a smooth way that minimizes excess strain in the wrong place.
13. Visualize your boat going through a narrow channel of poles stuck in the ground. Every stroke, you grab a pole and pull yourself past it. Remember, you are moving the boat past the paddle. Ideally, the paddle is stationary in the water. If you are moving water, that means your blade is moving and that is wasted effort. Your blade should be almost silent.
14. Dynamic, dynamic, dynamic!