Strength is specific to joint angles. Simply put, the range of motion in which you build the strength is the range of motion which will get strong. Other ROMs likely won’t. This is another bit of info I’ve bandied about here. I originally got it from Mike Tuchscherer (al0ng with a lot of my knowledge). Using this information we can deduce how static holds will affect the strength of the competition lifts. I’m calling static holds in this instance where you simply hold the bar at lockout. This doesn’t include other kinds of isometric movements like Pause Squats.
We’ve already discussed how static holds affect the deadlift. They are the best way to train your grip for the Deadlift. But how do static holds affect the strength of the squat and the bench press? Given the above axiom… they probably don’t. There is no ROM for static holds and outside of training the strength necessary to unrack the bar they are unlikely to significantly contribute to your strength throughout the lift. Does that mean they are worthless?
Static holds might not physically strengthen you but we need to consider another way they might build strength: psychologically. How often do you unrack the bar in the quest for a new PR and go “Oh shit”. How often do you make those “Oh shit” lifts? Probably less than when you confidently unrack the bar and let your instinct do the lifting. Static Holds can lessen those “Oh shit” moments and for that reason alone they are useful.
Here’s a good way to increase confidence in your setup and unrack. Which lift are you less confident at, the squat or bench press? Pick a heavy weight that you’re working towards and do a few static holds after your main sets. Unrack the bar and hold it until just before you start to shake. Treat these with respect; be careful. You can even increase the number of static holds you do over the weeks. It’s likely once you perform the lift in its entirety you’ll have lost the “oh shit” factor you used to have at that weight.