The Multi-Poundage System (MPS) was first introduced by Henry Atkins in 1949. Henry provides an update in this article. MPS was later rebranded as Drop Sets and claimed by Joe as one of the “Weider Principles”.Source: Peak Muscle Maker (March 1970) Page #6 -Peak Muscle Maker (Mar 1970) Page #7 -Peak Muscle Maker (Mar 1970)