Refer to Figure 1 . At Point A you will see an example of a swimmer who is lifting the elbow too soon out of the water and not pulling all the way through during the underwater portion of the stroke. This will result in less distance covered per stroke and more strokes taken over a given distance and even more importantly, more energy wasted. Now, take a look at Figure 2. This not only moves the swimmer forward farther per stroke, it also reduces the number of strokes the swimmer will take over a given distance.
Fewer strokes means less energy spent.
And less energy spent per stroke equals greater endurance allowing you to build your swim distances quicker and easier. Drop your arms by your side and mentally mark where your thumbs naturally line up with each thigh. Once swimming freestyle, you want to lightly drag your thumb across this spot during the underwater pull-through. Very simply, this drill taps into your muscle memory. You want to get used to pulling all the way through extending the arm behind you.