The effect of task-specific pain-related fear on object-lifting kinematics varies between individuals with and without repetitive lifting tasks during work

To investigate whether the effect of task-specific pain-related fear on lifting kinematics differs between adults with and without repetitive lifting tasks during work.

The sample comprised 156 healthy adults, divided into two groups: LIFTERS (postal service employees, n=76) with an occupation that involves repetitive lifting, and NON-LIFTERS (n=80) without such activities during work. All participants completed the Photograph Series of Daily Activities – Short electronic Version (PHODA‐SeV) and intuitively lifted a box of 5- and 15kg. Sagittal lumbar spine range of motion (ROM) was measured using a portable strain gauge-based system, while whole-body lifting strategy was quantified from conventional video recordings using the Stoop-Squat-Index at 30, 50 and 70% of the lifting cycle. The fear of round-back lifting was expressed by the score of the PHODA-SeV item no.3: PHODA-Lift (0-100). We fitted a linear model for each outcome of interest (lumbar spine ROM and Stoop-Squat-Indices) with group, PHODA-Lift, and group×PHODA-Lift interaction as independent variables, controlling for sex, age, and BMI.

PHODA-Lift median scores were 59.5 for NON-LIFTERS and 80.0 for LIFTERS. The fitted model revealed a statistically significant group×PHODA-Lift interaction effect on lumbar spine ROM during 15kg box-lifting (lifting up: 0.098, p=0.03; putting down: 0.101, p=0.035). For NON-LIFTERS, the PHODA-Lift demonstrated a significant effect (lifting up: -0.07, p=0.027; putting down: -0.13, p0.001). For LIFTERS, no evidence of a PHODA-Lift effect was observed. No group×PHODA-Lift interaction effect was identified for lumbar spine ROM during 5kg box-lifting or for Stoop-Squat-Indices.

The effect of task-specific pain-related fear on lumbar spine ROM differs between adults with and without repetitive lifting tasks during work. In NON-LIFTERS, elevated levels of fear of round-back lifting were associated with a reduction in lumbar spine ROM during 15kg box-lifting. This aligns with previous studies in the general population and may be interpreted as a “stiffening mechanism” to protect the spine. The absence of a corresponding association in LIFTERS might be explained by their distinctly higher PHODA-Lift scores, which could have concealed potential relationships through a ceiling effect. However, the increased PHODA-Lift scores in LIFTERS indicate a pronounced belief that lifting with a rounded back is dangerous (possibly learned from manual handling training), which does not seem to be reflected in the lifting behavior of these workers.

These findings contribute to a better understanding of the interaction between pain-related fear and lifting kinematics. Future research is required to determine its clinical relevance by investigating potential causal relationships between pain-related fear, lifting behavior, and low back pain.