Ground Time
The key difference between running and walking is that when running, there is a period of time that both feet are off the ground. The more time your feet are on the ground, the less time you are moving forward. An efficient stride spends enough time on the ground to power up for the next stride and not a millisecond more.
Form Power
What’s Form Power – this is essentially the amount of power wasted due to inefficiencies in your running form. Just like ground contact time above, the lower the number, the better and more efficient the runner. Be sure to see how your form power changes as your body fatigues during a run as breakdowns in form are likely to occur. So remember, better efficiency = less wasted energy = lower form power.