My father's trademark was letting go of the top hand after impact. But I do not isolate it in that fashion. I teach my students to utilize the four Lau Laws that will make them great hitters, and that if they do it correctly, they will have to let go with the top hand after impact!
When Mark McGwire shattered Roger Mans' single-season homerun record, The Sporting News ran a story on the changes that McGwire had made in his swing. It pointed out that the turning point in McGwire's rise from inconsistent slugger to home-run legend occurred when he adopted my father's one-hand extension principle.
Some baseball people put it this way: McGwire became a great power hitter when he began to release his top hand after impact. The truth is that he became a great hitter when he adopted the "four secrets to the swing."
A top-hand release is the result of a maximum lead-arm extension and a high finish. Amazingly, the knock on this method of releasing the top hand (that my father suggested more than 20 years ago) was that it reduced the hitter's power.
Tony LaRussa, McGwire's manager with the Cardinals, disputed the old-school hitting coaches who claimed that my father's methods did nothing but promote soft singles to the opposite field.
The truth, LaRussa argued, was that my father taught line-drive hitters to use the whole park, thus making them more productive.
When my father instructed a true home-run hitter like a Greg Luzinski or a Carlton Fisk or a Harold Baines, he taught them to use a slight uppercut with a full extension. LaRussa, noting the distinguished home-run success of McGwire, Sammy Sosa, and Ken Griffey Jr. the past few years, recently said, "A lot of us who are tremendous fans of Charley Lau know that he's up there smiling because there's a certain amount of vindication for that style of hitting he taught."
You have only to look around the major leagues to see that a top-hand release is a great benefit, not a deterrent to a player's power production. The list of top-hand devotees is impressive and long. Besides the aforementioned three, you can add such sluggers as Juan Gonzalez, Tino Martinez, Fred McGriff, Manny Ramirez, Dante Bichette, Tony Clark, Andres Galarraga, Frank Thomas, Jim Edmonds, David Justice, Shawn Green, and Todd Walker.
And that's just a small sampling. What these players have in common is that they all can hit more than 30 home runs a season.