At any rate.
I’ve been using kettlebells in conjunction with my Oly lifting for almost a decade now and while there are many similarities there are also many differences, technically, which must be respected. I’ve always felt the swing was very rich in both practical training application for weightlifters but recently I made a connection (that I don’t think I consciously made before) between what happens in the barbell lift off from the floor to above the knees and the kettlebell backswing.
First,from a power production standpoint the first pull functions in the same way as the backswing on the kettlebell two hand swing. The hammies and glutes are stretched and loaded which is followed by an explosive hip extension, knee extension and straightening of the torso.
The big difference of course is that a kettlebell can be swung between the legs and the barbell can’t. The best we can do with the barbell is to sweep the bar back as the knees are straightened and shins are pushed back to vertical. What is strikingly similar however is the posture of the olympic lifter when the bar is above the knee and the posture of the kettlebell lifter on the backswing of the swing.
Speed of the first pull, like the speed of the KB backswing also determines the intensity of the hamstring stretch reflex response. The faster the shins get to vertical, the faster the hammies stretch and the more explosive will be the strech reflex, which determines how fast the knees rebend under the bar and the speed of the hips to the bar. The knee rebend also causes a prestretch of the quads and the faster this prestretch the more powerful the quads will then straighten the knee. (Bud Charniga has a great article on his site that discusses this very topic which played a big role in this ah ha! moment) In the high level lifter, after the bar clears the knees, lifting it further is a result of an explosive chain reaction of stretch reflex responses.
I’m still fleshing it out, I’m rolling out the concept that the first pull is "winding up the spring". Of course, the stronger the hammies, the more power the stretch reflex will have, a good reason to also practice both heavy and mderately heavy kettlebell swings for strength and power. .
Anyway, if your second pull is sluggish, add more acceleration to the first pull and see if that helps. And throw in some kettlebell swings for additional work at the end of the workout.