Here is an article from “Tri Newbies Online” website
Closed Fist Drill
The Closed Fist drill is a terrific freestyle stroke drill that helps the swimmer optimize the underwater pull-through
Without even thinking about it, most of us rely on the palms of our hands to pull us through the water and propel us forward when swimming freestyle.
And why not?
It makes sense.
For when we swim freestyle we use our arms and hands like the paddle of a canoe. When paddling a canoe, we use the wide, flat end of the paddle, that which provides the greatest surface area, to propel us forward through the water. We certainly do not use the pole portion of the paddle to drive us through the water. So it goes without saying, the surface area of the hand, like the base of a canoe paddle, provides us with our greatest underwater pulling power.
Unlike the pole portion of a canoe paddle, our arms and specifically the underside of our arms, do provide additional surface area and thus additional power to our overall freestyle arm stroke.
And developing a feel for our arms under the water will only enhance our swim stroke and boost our overall distance per stroke. Unfortunately, most of us being triathletes do not consider the importance of the arm, and in particular, the underside of the arm, during the freestyle stroke.
Now, some of you may think you are getting plenty of power from your arms and hands and do not see the need to improve the feel of the underside of your arms during the underwater pull-through. However, you will be surprised just how much you do rely on the palms of your hands. And the “Closed-fist Drill will reveal this.
The Drill: The drill is fairly self-explanatory. You are basically swimming freestyle with a closed fist. However, some of us tend to want to cheat just a bit once we discover the lack of “feel” we have for the water when we aren’t using the palms of our hand. And in doing so, we open our fist slightly, similar to that of a Karate Chop. This is not correct! Below, you will see an example of the right way to swim this drill and the wrong way! Keep the fist closed! It won’t take long for you to realize how much you have been relying on the palms of your hands for power during freestyle. Initially, you will feel like you are going nowhere when swimming freestyle with a closed fist. And, at first, you will be slower. But you will develop a feel for this as your arms begin to play a significant part in your underwater pull-through. Remember, the pull-through must be complete for this drill to work (see section on Thumb-to-Thigh drill).
Drill Set: 10 x 25’s Closed Fist Drill. 15 seconds rest between each 25 yard swim. Adjust your rest accordingly.