Here is a breakdown of how to achieve the ideal forward lean in running:

• Keep your core up and tuck in your hips
• Hinge at your ankles and not your hip!
  Running is falling with style!

A proper forward lean ensures that your body's center of mass (located around your hips) stays slightly ahead of your feet.

Principles of Natural Running with Dr. Mark Cucuzzella

https://www.youtube.com/watch?v=zSIDRHUWlVo

Lifting your feet higher costs LESS energy when running

https://www.youtube.com/watch?v=Jj9ZgQgQvBk

Relax and let your feet kick up!