Objective: The aim of this study was to explore whether the Variable Lifting Index (VLI) can be corrected for cumulative mass and thus test its efficacy in predicting the risk of low-back pain (LBP). Background: A validation study of the VLI method was published in this journal reporting promising results. Although several studies highlighted a positive correlation between cumulative load and LBP, cumulative mass has never been considered in any of the studies investigating the relationship between manual material handling and LBP. Method: Both VLI and cumulative mass were cal- culated for 2,374 exposed subjects using a systematic approach. Due to high variability of cumulative mass val- ues, a stratification within VLI categories was employed. Dummy variables (1–4) were assigned to each class and used as a multiplier factor for the VLI, resulting in a new index (VLI_CMM). Data on LBP were collected by occupa- tional physicians at the study sites. Logistic regression was used to estimate the risk of acute LBP within levels of risk exposure when compared with a control group formed by 1,028 unexposed subjects. Results: Data showed greatly variable values of cumu- lative mass across all VLI classes. The potential effect of cumulative mass on damage emerged as not significant (p value = .6526). Conclusion: When comparing VLI_CMM with raw VLI, the former failed to prove itself as a better predictor of LBP risk. Application: To recognize cumulative mass as a mod- ifier, especially for lumbar degenerative spine diseases, authors of future studies should investigate potential asso- ciation between the VLI and other damage variables. Keywords: manual materials handling, job risk assess- ment, low-back pain, biomechanics, cumulative mass, cumulative load INTRODUCTION In 2003, International Organization for Stan- dardization (ISO) Standard 11228 Part 1 (ISO, 2003) introduced daily limits for cumulative mass for both lifting and carrying activities. However, although several studies have shown the presence of a positive correlation between cumulative load and low-back pain (LBP; Coenen, Kingma, Boot, Bongers, & van Dieën, 2013; Kumar, 1990; Norman et al., 1998), cumulative mass, calculated as product of mass and frequency of lifting, has never been taken into consideration when investigating the rela- tionship between manual material handling and LBP (Garg et al., 2014; Lavender, Oleske, Nich- olson, Andersson, & Hahn, 1999; Lu, Waters, Krieg, & Werren, 2014; Neumann et al., 2001; Norman et al., 1998; Wang et al., 1998; Waters et al., 1999; Waters, Lu, Piacitelli, Werren, & Deddens, 2011). McGill (1997) hypothesized that two differ- ent failure modes of a vertebral unit (vertebrae, discs, ligaments, and facet joints) can occur: a single overexertion that exceeds tolerance limits of the spinal unit or repeated submaximal exer- tion that can result in diminished tissue toler- ance, eventually damaging the vertebral unit. Commonly used to assess manual material lifting-related risk, the Revised National Institute for Occupational Safety and Health (NIOSH) Lift- ing Equation (RNLE) method (Waters, Putz- Anderson, & Garg, 1994) combines both peak and cumulative load in its “number of liftings per minute” parameter in relation to the duration of the lifting activity. When the lifting rate is below one lift every 10 min, the recovery period coeffi- cient usually falls in the 1-hr category (Waters et al., 1994); clearly, this approach is very conserva- tive. However, in situations of low lifting rates, the 732413HFS XX X 10.1177/0018720817732413Human FactorsVariable Lifting Index Adjusted for Cumulative Mass Address correspondence to Giulia Stucchi, Department of Services and Preventive Medicine, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Via San Barnaba, 8, Milan, 20122, Italy; e-mail: giulia.stucchi@policlinico.mi.it. Cumulative Mass and NIOSH Variable Lifting Index Method for Risk Assessment: Possible Relations Giulia Stucchi, Natale Battevi, Fondazione Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy, Monica Pandolfi, Università degli Studi di Milano, Milan, Italy, Luca Galinotti, Fondazione Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy, Simona Iodice, and Chiara Favero, Università degli Studi di Milano, Milan, Italy HUMAN FACTORS Vol. 60, No. 1, February 2018, pp. 57–67 DOI: 10.1177/0018720817732413 Copyright © 2017, Human Factors and Ergonomics Society.