Regression Equation between Required Force and Lumbar Load of Caregiver in Supporting Standing-up Motion via Computational Musculoskeletal Simulation

Abstract

Caregivers experience low back pain because of patient handling such as supporting standing-up. The lumbar load of a caregiver depends on the required force for patient handling motions. If the relationship between the required force and the lumbar load is quantitatively clarified, it may be useful for preventing low back pain in caregivers. In this study, we investigated the quantitative relationships between the required force and lumbar loads such as vertebral stress and muscle activity in supporting standing-up by computational musculoskeletal simulation. First, a musculoskeletal model of a caregiver was prepared, and then the model performed simulated supporting standing-up motions. The vertical load used as the required force was placed on the upper limb of the model. The compressive/shear stress of the vertebral (L4–L5) and muscle activities of spinae erector muscle group were recorded as the lumbar load. The results showed that there are highly significant correlations between the required force (r > 0.9, p < 0.01). In addition, regression equations for predicting each lumbar load by the required force with highly determination coefficients (R2 > 0.9) were obtained from these relationships. Furthermore, we found that when the required force was more than 120 N, the compression stresses of the vertebral exceeded injury threshold (3400 N) by the regression equation. These regression equations contribute to quantitatively consider lumbar loads of caregiver during patient handling based on injury thresholds and the required force.

Foot Position Measurement during Assistive Motion for Sit-to-Stand Using a Single Inertial Sensor and Shoe-Type Force Sensors

“…Lee et al revealed that the COP shifted to the left side when the right foot was placed forward [ 23 ]. Moreover, previous studies have shown that shoe-type force sensors could be used to recognize occupational postures, including different foot positions [ 24 , 25 ], and to monitor trunk movement, lumbar load, and arm movement during manual handling [ 19 , 25 , 26 , 27 ]. From these findings, we hypothesized that foot position can be estimated on the basis of the distribution of the ground reaction force on the foot that is obtained from shoe-type force sensors.…”