To 'grease the groove' for strength development, lift weights at 75-85% of 1RM for about half or fewer of the maximum possible repetitions.

“you have to address uh the issue of specificity so specificity pretty much means without getting too too much into the weeds to get stronger first of all you need to lift weights that are heavy enough and uh if you're looking about percentages of one R Max we're looking at like 75 to 85 typically if you go to light you don't make the impression on your nervous system and it's just not specific enough if you go to heav very quickly you're just going to burn yourself out and uh so pretty much like it's a weight That's Heavy enough to respect and light enough not to fear and second of all and this is very surprising is you only do about half or fewer reps that you possibly could do”