What's the pre-stretch? Like side bends, broom stick stretch? Good to do these in between sets yeah.
pre-stretch is the integral part of productive exercise and has nothing to do with the bull shit , nonsense and lies that is pushed today.
let me use the pull-up or chin-up as an example;
you see most trying to get 10 or 15 reps, where in reality, done correctly could only achieve 5, they do this by limiting the range of motion and moving so fast they are unable to maintain constant tension of the muscles being stimulated.
the pre-stetch of this exercise is at the end of the negative portion of the movement, where you hang and your body weight is pulling the muscles involed in the movement, if one lowers too quickly or in the worse case just drops, the muscles will contract, but if you move slowly, very slowly in the negative, the muscles will not contract or spasm as a protective response and you will be able to safely move into a position of full extension under load, which is the key for healthy flexible and strong joints.
other examples, the chest pad of a row should be set so that you can barely grab the handles.
the bench press, the hands positioned at the right width ensure maximum pre-stretch.
All proper exercises will have the ability to apply pre-stretch, if it doesn't then the exercise is not a true exercise.