Rod action refers to the taper design built into a rod. The butt of the rod is where you get most of your power. The tip is where you get your sensitivity. The rod design between the two will determine how the rod performs in key areas, such as the cast, the hook set, and the retrieve.
Most rods are built from rolled sheets of carbon fiber or fiberglass. Some rods will have a braided over-wrap, mostly for aesthetics, but for those that don’t you may be able to see the edge of the sheet going down the length of the rod. The shape of the sheet before the rod is made will determine the action of the rod.
Most rods can be categorized as follows:
Slow – Slow action rods will bend deeply throughout their length. Fiberglass rods are often slow action rods, more so because of their composition rather than the type of taper that was built into them. Slow action rods cast heavy lures very nicely, but have very poor, “mushy” hook sets. Slow action rods would also be preferred on larger game, where a rod is likely to be severely bent, such as the case with catfish and striper rods.
Medium – Medium action rods are the workhorse of the recreational fishing world. If you could only fish with one rod, it would probably be best to select a medium action rod. You will find good hook-setting power without too fast of an action.
You can use medium action rods for just about everything, but your jig and worm rods should probably be no faster than medium. The reason for this is that medium action rods have more “beef” at the tip which has a better feel when pulling jigs and worms through thick cover. These rods would also be a good choice for lures brought in on a steady retrieve, such as spinnerbaits, and crank baits.
Fast – These rods have a softer tip, and as such, bend more at the tip than throughout their length. Fast action rods deliver shockingly good power, while still having a soft tip to detect soft bites, lure vibrations, and other subtle information.
The soft tip also gives a little different feel when working lures. Fast action rods are great for jerk baits and top water lures. The extra spring of the soft tip gives these lure a little more action. If twitching a crank bait, a fast action will work in the same way; giving a little extra action to the lure.
Ultra Fast – Ultra fast rods take “fast” to an extreme. They deliver the most power to the hook-set, and have the greatest sensitivity at the tip.
Your dropshot should be an ultra-fast action, and is probably the best example of where this type of action excels. The super-soft tip lets you detect the lightest of bites without alarming the fish. During dropshot fishing, a spot may nibble at the offering gently several times before committing, and the ultra-fast action lets you observe these nibbles without letting the fish detect that something is pulling against it. Once the fish commits, you can lift the rod sharply and put direct, firm pressure on the fish very quickly.