If you can hold your planks for minutes, you need to stop doing planks the way you’re doing them.
You should do your next plank in front of a mirror, or film yourself, so you actually see what your posture looks like.
Is your lower back swaying? Does your upper back hunch over? Do your hips sag to the floor? These are all compensations that indicate you’re performing your plank with improper mechanics.
The more you can integrate all your muscles to align the structures of your body at once (straight spine, hips and shoulders level), the more intense the plank is going to be, and the less time you’re going to be able to hold it.
The plank is not an exercise for your shoulders and arms, and only feeling the burn there.
The plank is meant to burn into your stomach primarily, secondly into your upper back, and then your glutes.
But if you’re not feeling any of these muscles working, then you’re just going through the motions of what looks like a plank.