The paper at hand extends previous research on ergonomic lot-sizing and introduces a new mathematical model that integrates ergonomic and economic aspects. A rest allowance function is used to take account of recovery periods that help to maintain low levels of fatigue and ergonomic risks. As recovery periods represent non-productive time, the developed integrated model permits to estimate the economic impact of different workload levels. Finally, the model is applied in a numerical study, reflecting a typical manual material handling process. Based on the results of a parametrical analysis, we illustrate the applicability and validity of this approach to different industrial contexts.