Minimizing maximum job dependent ergonomic risk.

We study a problem, in which workers must be assigned to jobs over a number of time periods and each assignment incurs a job dependent ergonomic risk for the worker. The risks of the same worker are summarised over the time periods. The objective is to minimise the maximum risk of all workers. The problem has an interesting combinatorial structure such that it is not immediately clear if it is polynomially solvable or NP-hard. Its computational complexity remained open for 35 years. We prove its NP-hardness and discuss polynomially solvable special cases, in which either the number of workers is fixed or optimal solutions are attained at a lower bound. The results can be used in production planning approaches considering elimination of excessive ergonomic risks as one of the objectives. [ABSTRACT FROM AUTHOR]