If you were to plot improvement over time on a run chart, backsliding would give the curve a saw-tooth look to it. A gain followed by a drop, followed by a gain and another drop.
Backsliding is reduced by standardization (i.e. by using Standard Work). It can also be completely prevented by removing tools necessary to do a process ‘the old way.’ This step accelerates the pace of improvement, since there is not a drop after each gain.