I like this resource from RunnersWorld it breaks down what each part of the body should be doing. – Laney H https://www.runnersworld.com/beginner/a20811257/proper-running-form-0/
Your legs: Everyone’s stride and gait is a little bit different, and that’s okay. “But the easiest way to think about your lower body is to think about your shin being as close to perpendicular as possible when the foot hits the ground,” Mahon says.
If a person is a heavy heel striker, their angle is too big; if they’re a forefoot striker, their angle is too small. Either way, it’s a negative position to be in because you’re opening yourself up to injuries in the other foot or knee. “You also won’t be using all the joints you have properly in the right timing sequence,” he says. “If you land at that 90-degree angle, then you get to use your ankle, your knee joint, and the hip joint all at the same time to both absorb shock and then create energy.”
Your Feet: There’s no right or wrong way for your feet to hit the ground, as long as you’re actually using them to push off (instead of just lifting them). That said, the idea is to aim to hit the road with the ball of your foot, Fierras says. “That’s going to help you propel forward better, and your stride won’t come out too far in front of you.”
Running on your toes or striking with your heel are both more likely to set you up for injury. If that’s how you run naturally, though, “rather than focusing on changing your stride, talk to an expert about getting into a proper shoe—maybe one with more cushioning—that will help you stay injury-free,” Nurse says. Everyone’s natural footstrike and gait is different, so you want to make sure you’re optimizing yours best for your body.
Other helpful resources:
https://www.youtube.com/watch?v=Rt9hgtFzZk0 this one give explanations and hen how to improve then their actual website explains why you might be a heel striker. https://therunexperience.com/proper-running-footstrike-3-steps-to-improve-it/