If you use a lighter kettlebell, you'll maximize velocity but you won't activate your glutes as much. (cathe.com)
When you're using thick padding, then the pain goes away and you can activate the glutes better. (completehumanperformance.com)
Side benefits to activating the glutes prior to a workout (or making sure your muscles are firing in general) is that you'll see the results of your work a lot faster. (thebettyrocker.com)