The mind-muscle connection is a widely debated topic when it comes to movement execution and proper technique. Should you focus “internally” by thinking about what muscles you’re supposed to be targeting with each exercise? Or should you focus “externally” by thinking about using your body as a whole?
As is usually the case, I think that the answer is not black and white but rather depends on the context. Generally speaking, the mind muscle connection should only be used sparingly (if at all) on primary exercises like squats, deadlifts and overhead presses, as these are highly technique-focused exercises that will activate a large muscle mass regardless of attentional focus. For these movements, it is better to focus on the movement of your entire body and simply execute the exercise with proper technique and through a full range of motion. For all tertiary exercises (isolation exercises) and any remaining compound exercises, you can use the mind-muscle connection to increase activation of the target muscle, as you feel appropriate.
For the record, research has shown increased muscle activation when subjects are instructed to use “internal cueing” (such as squeezing your glutes as hard as possible to get the barbell to move in a hip thrust) as opposed to “external cueing” (such as simply moving the barbell upwards). In addition, recent data has suggested that use of a mind-muscle connection can be used to enhance muscle hypertrophy. So while it may not be appropriate for all exercises, practicing and cultivating a strong mind muscle connection is well-advised if your goal is to achieve the best muscular development possible.
In summary, our goal with training is to maximize muscular tension with relatively large training volumes and as outlined above, the best way to do that is by honing in on your technique.