ASSOCIATIONS BETWEEN PAIN-RELATED FEAR AND OBJECT LIFTING BIOMECHANICS ARE LIKELY DEPENDENT ON OBJECT WEIGHT

C. Bangerter^1,2, M.L. Meier³, M. von Arx¹, M. Liechti¹, S. Schmid^1,2

¹Spinal Movement Biomechanics Group, Bern University of Applied Sciences, School of Health Professions, Division of Physiotherapy, Bern, Switzerland, ²University of Basel, Faculty of Medicine, Basel, Switzerland, ³Integrative Spinal Research, Balgrist University Hospital, Department of Chiropractic Medicine, Zurich, Switzerland

Background: Recent evidence has demonstrated that the fear of lifting an object with a “round back” is associated with reduced sagittal plane lumbar spine flexion angles during lightweight object lifting in healthy pain-free individuals. These findings were linked to a potential protective movement strategy with possible negative consequences in the long term. However, no associations between measures of pain-related fear and whole-body lifting behavior (i.e., stoop vs. squat) were observed, suggesting that fear of round-back-lifting might only affect spinal kinematics and not directly influence whole-body lifting strategies. Since previous studies only focused on lightweight object lifting, it remains unclear whether these results also apply for lifting heavier objects.

Purpose: This study aimed at investigating the associations between pain-related fear and the biomechanics of lifting a 15kg-box in healthy individuals.

Methods: Thirty healthy individuals (m/f: 20/10; age: 31.8±8.5 years; BMI: 23.3±2.4 kg/m²) participated in this study. All participants completed the Photograph Series of Daily Activities - Short electronic Version (PHODA‐SeV) and were equipped with 58 retroreflective markers. Subsequently participants were asked to intuitively lift up and put down a 15kg-box. Kinematic data were recorded using a 16-camera Vicon motion capture system and continuous sagittal lumbar spine angles were calculated. Whole-body lifting strategy was quantified using continuous Stoop-Squat-Indices and the fear of round-back-lifting was operationalized by the score of the PHODA-Lift item (0-100). To analyze associations between continuous lifting data and the fear of round-back-lifting, Statistical Parametric Mapping-based multiple linear regression analyses (controlled for gender and BMI) were performed.

Results: The results indicated time-specific negative correlations between the PHODA-Lift score and the Stoop-Squat-Indices during the lifting-up phase (17-35% of lifting-up cycle, -0.43≤r≤-0.42, p=0.047), indicating more squatting behavior in individuals with higher levels of pain-related fear. However, no statistically significant associations between the fear of round-back-lifting and sagittal plane lumbar spine flexion angles were observed over the entire lifting cycle.

Conclusions: Associations between pain-related fear and object lifting biomechanics seem to be dependent on object weight. Contrary to previous studies on lightweight object lifting, the results of this study demonstrate an association between fear of round-back-lifting and whole-body lifting behavior but no association with lumbar spine kinematics. Since this study only focused on lifting a 15kg-box, a direct comparison of lifting biomechanics between different box weights is not possible. However, the findings suggest that participants overall might adopt less spinal flexion when lifting heavier weights, which could have concealed differences in spinal kinematics between individuals with different levels of pain-related fear. Moreover, the increased squatting behavior in fearful individuals might be interpreted as an expression of “spinal protection” by lifting the weight predominantly using lower extremity muscles while keeping the spine as vertical as possible. Future studies might therefore investigate the effect of different weights on lifting biomechanics in healthy individuals.

Implications: This study contributes to a better understanding of how pain-related fear is associated with lifting biomechanics in healthy pain-free individuals. Furthermore, the findings highlight the importance of assessing both, spinal kinematics and whole-body lifting strategy when investigating lifting behavior.

Funding acknowledgements: None.

Keywords:
Stoop-Squat-Index
Spine
Fear of movement

Topics:
Musculoskeletal: spine

Did this work require ethics approval? No

Reason: The responsible ethics committee provided exemption for this study (Kantonale Ethikkommission Bern, Req-2020-00364) and all participants provided written informed consent.