Most caregivers have low back pain which results from frequent care activities such as assistance motion that supports transfer and standing-up. Various parameters are associated with the caregiver’s lumbar load. In this study, we focus on the foot position of the caregiver as one of the subjective adjustable parameters. This study aimed to analyze the relationship between foot position and stresses of the L4–L5 joint as lumbar load during supporting standing-up via musculoskeletal simulation. The musculoskeletal model was tasked with simulating supported standing-up motions based on a specific pelvic position and angular variation of each joint. The anterior foot (left foot) was fixed, and the posterior foot (right foot) was moved to three backward positions and three rightward positions, thus obtaining nine posterior foot positions. Compressive, anteroposterior shear, and lateral shear stresses of the L4–L5 joint were compared for nine foot positions. The results showed that as the anteroposterior distance and lateral widths between both feet increased, the average value of compressive/shear stress of the L4–L5 joint during motions decreased. From our findings, we hypothesized that the foot position may reduce the lumbar load and prevent low back pain.
[Purpose] In caregivers, low load posture is necessary to prevent lower back pain during
patient handling activities such as sit-to-stand support. This study focused on the
foot-position of caregivers as an adjustable and useful parameter. A wide stance decreases
the stress on the lumbar vertebra. However, this foot-position increases loading of the
spinae erector muscles. The aim of this study was to investigate the relationship of
anterior-posterior and lateral-medial distances between feet and activity of the spinae
erector muscles to determine the optimal foot-position for reducing stress on the lumbar
vertebra without increasing spinae erector muscle load. [Participants and Methods] Five
young male participants were asked to provide sit-to-stand support 10 times using nine
normalized foot-positions with different anterior-posterior and lateral-medial distances.
Surface electromyograms of the erector spinae and lower limb muscles were measured during
sit-to-stand support. [Results] The results showed that the optimal foot-position
(anterior-posterior 55%, lateral-medial 20% of body height) increased muscle activity
within the lower limb muscles compared with the lower back muscles and did not increase
loads on the erector spinae muscle. [Conclusion] Optimizing foot-position can reduce
stress on the lumbar vertebra without increasing load on the spinae erector muscles.
Caregivers experience lower back pain due to their awkward postures while handling patients. Therefore, a monitoring system to supervise caregivers' postures using wearable sensors is being developed. This study proposed a postural recognition method for caregivers during postural change while handling a patient on a bed. The proposed method recognizes foot positions and arm movements by a machine learning algorithm using inertial data on the trunk and foot pressure data obtained from wearable sensors. An experiment was conducted to evaluate whether the proposed method could recognize three foot positions and three arm movements. Participants provided postural change for a simulated patient on a bed (patient: supine to lateral recumbent) under nine conditions, including different combinations of the three foot positions and three arm movements; the experiment was repeated ten times for each condition. Experimental results showed that the proposed method using an artificial neural network with all features obtained from an inertial measurement unit and insole pressure sensors could recognize arm movements and foot positions with an accuracy of approximately 0.75 and 0.97, respectively. These results suggest that the proposed method can be used in a monitoring system tracking a caregiver's posture.
Assistive motion for sit-to-stand causes lower back pain (LBP) among caregivers. Considering previous studies that showed that foot position adjustment could reduce lumbar load during assistive motion for sit-to-stand, quantitative monitoring of and instructions on foot position could contribute toward reducing LBP among caregivers. The present study proposes and evaluates a new method for the quantitative measurement of foot position during assistive motion for sit-to-stand using a few wearable sensors that are not limited to the measurement area. The proposed method measures quantitative foot position (anteroposterior and mediolateral distance between both feet) through a machine learning technique using features obtained from only a single inertial sensor on the trunk and shoe-type force sensors. During the experiment, the accuracy of the proposed method was investigated by comparing the obtained values with those from an optical motion capture system. The results showed that the proposed method produced only minor errors (less than 6.5% of body height) when measuring foot position during assistive motion for sit-to-stand. Furthermore, Bland–Altman plots suggested no fixed errors between the proposed method and the optical motion capture system. These results suggest that the proposed method could be utilized for measuring foot position during assistive motion for sit-to-stand.
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