According to the law of physics, acceleration is the rate of change of velocity of an object with respect to time, and as we know "...The vector of the net force acting on a body has the same direction as the vector of the body's acceleration". In running (and other sports or bodies in motion) the velocity can be or should be constant (pace) and therefore the acceleration will also be constant, but we know that it's unbelievably hard to keep the same pace during training or competition. This is telling us how important it is to do the right thing.
The result of your interaction with forces is to minimize the negative effects of bad performance. As a result when you are reducing or change the velocity because of your lack of technique, the acceleration becomes a negative ratio. Thus, the reduction in velocity automatically gives you a negative acceleration. One of the key actions in POSE METHOD technique is to land in line with your center of gravity, this allow you to keep you in motion without reducing the velocity and therefore keeping the acceleration positive....wondrously clever.
OBSERVATION: This is not a simulation. This is real analyzes from a physics software (Tracker is a free video analysis and modeling tool built on the Open Source Physics (OSP) It is designed to be used in physics education.