Since I will be coaching Danny and John for crawl strokes, I started to go back to the pool to practice and observe other swimmers.  Comparing what I observed in the pool with the lecture Dave Scott gave, I did find those common "mistakes" swimmers would make that Dave mentioned in "efficient swimming".

Few points Dave mentioned really worth paying attention to,

1. keep the head at neutral position, looking straight down!
2. hand entry out and front aligning with shoulder, entering the water halfway between head and arm's full extension.  4 fingers should enter the water first.
3. extend arm, flex in the wrist then set in the elbow.
4. don't drop the elbow



Though Dave told "extend arms to 170 degrees elbow flexion", I actually extend the arms fully (straighten the arms), and keep full extension as the other arm pulls, enjoying gliding.  However, if the arms extend to 170 degrees elbow, then I would have saved some energy for extending from 170 degrees to 180, then flexion-in back to 170 degrees because this 10-degree to-and-fro does not produce any momentum.  Nevertheless, arms extend to the full length, the move appears more smooth.  How I swim is the hand enter the water halfway, then extend the arm fully, while the other hand pulling its shoulder is also escalating (due to shoulder rotation), then the extending hand extends further; at this moment the head faces to pulling hand side then flexion-in the wrist then elbow, starting to pull.

Besides Dave Scott, the educational vedio that Tomoko HAGIWARA (萩原智子) made is also very inspiring.





It had taken me very long practcing crawl before I could swim easily. However, in order to reinforce the intensity, I set 32min for 1.5k crawl as intensity benchmark.  Consequently, I got the tendinitis at elbows.  What a shame!  The elbow tendinitis is well-known as "tennis elbow".  Ironically, I did not get "tennis elbow" when I played tennis heavily, but from swimming which is generally believed to be a good complementary exercises to prevent sports injury.