So? As soon as the db's touch your chest muscles relax, as soon as you stand up in a squat muscles relax, as soon as you curl to the top muscles relax...what's your point?
Really, mine dont, if your muscles were not flexed and tight when you stood up in a squat you would fold under the weight.
Any time I use dumbells the tension never comes off the muscle.
We are talking a very specific area of the low back with box squats, L4 L5, go and see how many back injuries involve those discs.
that area is under huge compression once you sit down
Any way , fuck it you carry on doing them,
"Light weight baby"