If you can’t do it slow, then you can’t do it fast.
It’s pretty straight forward, too many people rush a movement and do it wrong.
Slow it down. If you’re making the mistake in the fast version, then use that slow version to practice and correct it.
It’s as simple as that.
It’s one of the best sweeping statements that I can make in exercises that fixes people’s mistakes (9 times out of 10).
For example, in squats, I often see people bounce the weight out of the bottom to squat it up. When they do this, they may bounce themselves out of a good bar path, then have to ‘good morning’ the bar into a good position, making them working harder than they should.
Tempo squats or paused squats may eradicate this poor technique, and help them build strength out of the bottom of the squat. Once practiced for a good period of time, their squat will most likely be improved.
Don’t get me wrong, this ‘bounce’ out of the bottom can work fine, so long as you don’t lose tension, nor a good bar path, but that’s usually with more experienced lifters that can actually achieve that.
There are of course exceptions to this ‘slow down’ rule.
You can’t slow down a movement that requires explosiveness to execute it (think Olympic lifts). However, you can take derivatives of those explosive movements to practice small portions of it.
For example, when I’ve had people struggle to utilise their hips in heavy KB swings, I get them doing what I refer to as a T-Rex swing. Your elbows stay stuck to your ribs when you swing with this technique, emphasising the use of the hips.
This usually corrects the hip extension portion of the swing, and gets the explosiveness in the swing working. It also can help people to pack their shoulders when they swing.
Once learnt, now back to normal swings, and this should be corrected.