The NLE adequately controlled the L5-S1 spinal loads during lifting activities in upright standing posture by yielding RWLs that correspond to compressive loads far smaller than the NIOSH action limit of 3400 N and shear loads smaller than 1000 N (Table 1: tasks 1 through 6). The NLE is therefore very conservative (Cupright < 2000 N) for these activities as far as the L5-S1 compressive load is concerned (Table 1). Also, the NLE adequately controlled the L5-S1 compressive loads to remain lower than 3400 N during almost all lifting tasks involving small trunk flexion angles (T < 30°) (tasks 7 through 14 with the exception of task 11 in Table 1). For all lifting tasks with trunk flexion angles larger than 30° (tasks 15 through 50), however, the proposed RWL of the NLE generated L5-S1 compressive loads up to 40% beyond the NIOSH limit of 3400 N. Also, for all lifting tasks in flexed postures the predicted L5-S1 shear load with the RWL in hands exceeded 1000 N (Table 1). Comparison of the maximum weight in hands (M3400) that results in the L5-S1 compression limit of 3400 N to the RWL for lifting tasks indicated greater RWL in lifting activities involving trunk flexion angles larger than 30° (i.e., RWL/M3400 > 1 and in some cases close or even larger than 2) (Table 2).