Human muscle strength definitions, measurement, and usage: Part II – The scientific basis (knowledge base) for the guide1 1The recommendations provided in this guide are based on numerous published and unpublished scientific studies and are intended to enhance worker safety and productivity. These recommendations are neither intended to replace existing standards, if any, nor should be treated as standards. Furthermore, this document should not be construed to represent institutional policy.The following individuals participated in the discussion of the earlier version of this guide. Their suggestions (written or verbal) were incorporated by the authors in this version: A. Aaras, Norway; J.E. Fernandez, U.S.A.; A. Freivalds, U.S.A.; T. Galleway, Ireland; M. Jager, Germany; S. Konz, U.S.A.; H. Krueger, Switzerland; K. Landau, Germany; A. Luttmann, Germany; J.D. Ramsey, USA; M-J. Wang, Taiwan.