A. S. Prilephin suggested that to achieve the proper intensity, one should use the rep/set scheme shown in the table, to ensure the greatest development of speed and strength. He discovered that if 7 or more reps were performed at 70%, the bar speed slowed and power decreased. The same holds true when using 80% or 90%; once one goes above the rep range shown, the bar slows, which translates to less power. Doing fewer or more lifts than Prilepin suggests will cause a decrease in training effect.
Here is a link to the chart....
http://www.angelfire.com/pe/txpls/prilephin.html