The Gait Cycle
Gait essentially is a transition between repeated loss of balance and recovery.
During movement there is a cyclic transfer between potential and kinetic energy which will minimize the energy cost of walking. Efficient movement involves preserving and transferring the greatest amount of energy (your momentum) to help propel you forward during your next step.
By sliding your feet, yes, the ground reaction force is minimized but you’re moving (and programming yourself in the future) to move inefficiently (by dragging your feet).
Besides friction, the net energy cost during gait is proportional to medial, lateral and vertical displacement of the body’s center of gravity. The greater the displacements, greater the energy costs.
Other considerations include width of base of support, angle of toe out, stance phase, period of double limb support, along with increasing the base of support will see an increase in the medial/lateral displacement – all of those increasing factors will serve to increase the M/L displacement of the COG which will require you to expend more energy.
3 Kinds of Forces
Contact with the ground results in one of 3 forces acting on the body during the stance phase.
are going to be equal and opposite, and included reactions to loading and propulsion, at mid stance these vertical forces are less than your body weight (BW).
Anterior and Posterior Forces
are designed to prevent the foot from slipping, at initial contact the AP force is directed post, it will peak at about 20% of the BW and is related to the bodies COG. As your foot first touches the ground, while entering swing, the forces will be directed anteriorly to help the body accelerate forward.
Medial Lateral Forces
tend to be smaller than other components and will vary with the base of support (medial / lateral forces are less if you walk with a small base of support because you would be getting more vertical support).
Just to clarify. What part of the foot (optimally) strikes first depends upon speed - Above ~120 steps/min you can no longer increase the stride length. This marks the transition from walking to jogging/running and occurs at ~190 cm/sec.
So you want to start jogging when you start to feel like you have to. Jogging too soon is similar to jogging in place (wasted effort and energy). Without going into plantar pressures and a joint by joint kinematics -- have a few days? ;) - I'll leave it there and can clarify further if needed.
My other answer may be helpful to you as well.