Running on the balls of the feet is absolutely the correct thing to do. I’ve been training athletes for more than 6 years and this is the first things that we go over, as it is on of the biggest misconceptions in sport/fitness mechanics.
If you are running distance, or even sub-maximal sprints for that matter, a heel strike comes natural only because you’re wearing cushioned shoes. Watch any of the champion marathon runners, especially the ones that go barefoot. The heel never strikes the ground. (in fact, I encourage anyone to go run barefoot, even if it’s just through the house. Heel strikes aren’t fun.)
It’s easier on the structure and for performance purposes, way faster. when the heel strikes the lower leg is at a negative angle (heel in front of knee at the point of contact) causing a braking/stopping force that slows the individual down until the ball of the foot gets under the hip. At that point, the individual must then re-accelerate through the push off.
When the ball of the foot strikes first, it is generally with a positive shin angle (pointing down and back, with the knee in front of the heel). This takes away the unnecessary ground contact time and braking forces.
This technique is more efficient, faster, and better for the human structure.
Like I always tell the athletes… If your heels are hitting the ground, you’re stopping.