Here is a post I found from Strength Coach Jonathan Fass:

Performing wrist extension exercises might actually be making your grip weaker. The functional role of the wrist extensors is to maintain an optimal length-tension relationship for the wrist and finger flexors to exert the greatest amount of torque when gripping and holding an object. Therefore, you can train the extensors to become stronger just by carrying objects, and not by performing active dumbbell or barbell wrist extensions. In fact, if you create a strength imbalance at the wrist in an attempt to get your forearms stronger for the sake of appearance, you could actually impact the ability of your flexors to grip strongly, impacting your weights on more important strength building exercises such as deadlifts, rows and pull-ups or chin-ups, which naturally and functionally train the wrist extensors, anyway.

Very interesting. Our grip strength routine usually uses pinch exercises or wrist rollers, but I can see where some lacrosse players would try wrist flexion or extension exercises. According to Jonathan we should stick to pinching or even using a farmer’s walk, which is holding two heavy dumbbells and walking for distance.

You can read more about Jonathan at www.acceleratedstrength.com.