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Morino S1, Takahashi M2
1Osaka Prefecture University, Department of Physical Therapy, Osaka, Japan, 2Keio University, Department of System Design Engineering, Yokohama, Japan
Background: Specific anatomical and physiological changes occur during pregnancy. These changes cause postural and movement instability and impose excessive strain on muscles, such as erector spinae (ES), contributing to low back pain (LBP). Sit-to-stand (STS) motion includes stretching and bending of the trunk and can potentially cause LBP. Thus, the determination of causative factors of LBP in STS based on assessments of not only motion but also muscle load by an objective assessment method is required for the management of LBP during pregnancy.
Purpose: The present study aimed to investigate the relationship among motion, muscle load, and intensity of LBP in STS motion using musculoskeletal model for pregnant women.
Methods: At first, motion analysis of STS motion was conducted in pregnant women to obtain motion, force, and electromyogram data by inertial measurement units, Wii balance board, and surface electromyography, respectively. Then, the participants were asked about pain intensity of LBP in STS motion by a Numerical Rating Scale (NRS). Subsequently, ES muscle torque in the STS was estimated from obtained data by using musculoskeletal model of pregnancy. Based on the value, root mean square of ES muscle torque (RMS-MT) was calculated as an evaluation index of ES muscle activation. The bigger values of the index indicate the greater activation of the muscle. Then, the difference of RMS of muscle torque in STS and at standing position (DRMS-MT-Stand) was also calculated in order to remove the individual differences of muscle activation in rest position. At last, the correlation analysis was conducted using the two indices of ES muscle torque and NRS score to investigate the correlation between the degree of muscle activation and the intensity of LBP by using the data from pregnant women who have LBP in STS motion. In addition, multivariate linear regression analyses adjusted for other factors related to LBP (age, variation of body mass index during pregnancy and pregnancy weeks) was performed to determine whether the intensity of LBP was associated with muscle activation.
Results: Among the participants, 9 women had LBP in STS motion (29.4±2.9 years, 34.6±1.9 weeks of pregnancy). The range of NRS score about LBP of them was 1-6 (Average score: 3.1±1.5). As the result of correlation analysis, no significant correlation between RMS-MT and NRS score was observed (r = 0.38，p = 0.32). On the other hand, significant positive correlation was observed between DRMS-MT-stand and NRS score (r = 0.74，p = 0.02). Additionally, this correlation was still statistically significant after adjustment for other factors related to LBP (β= 0.919, p = 0.02).
Conclusion(s): A positive correlation between the DRMS-MT-stand and the intensity of LBP was observed to be significant in spite of no significant correlation was observed in RMS-MT. From these results, greater ES muscle activation in STS motion compared with rest position might indicate a higher relationship with LBP during pregnancy.
Implications: For the management of LBP in STS motion during pregnancy, the assessment and approach to muscle activation during motion and also rest position might be effective. This relationship might be applicable to other motions that related LBP.
Keywords: Pregnancy, Low back pain, Biomechanics
Funding acknowledgements: This study was supported by JSPS KAKENHI (JP18H05962) and JKA promotion funds from KEIRIN RACE (28-143).
Purpose: The present study aimed to investigate the relationship among motion, muscle load, and intensity of LBP in STS motion using musculoskeletal model for pregnant women.
Methods: At first, motion analysis of STS motion was conducted in pregnant women to obtain motion, force, and electromyogram data by inertial measurement units, Wii balance board, and surface electromyography, respectively. Then, the participants were asked about pain intensity of LBP in STS motion by a Numerical Rating Scale (NRS). Subsequently, ES muscle torque in the STS was estimated from obtained data by using musculoskeletal model of pregnancy. Based on the value, root mean square of ES muscle torque (RMS-MT) was calculated as an evaluation index of ES muscle activation. The bigger values of the index indicate the greater activation of the muscle. Then, the difference of RMS of muscle torque in STS and at standing position (DRMS-MT-Stand) was also calculated in order to remove the individual differences of muscle activation in rest position. At last, the correlation analysis was conducted using the two indices of ES muscle torque and NRS score to investigate the correlation between the degree of muscle activation and the intensity of LBP by using the data from pregnant women who have LBP in STS motion. In addition, multivariate linear regression analyses adjusted for other factors related to LBP (age, variation of body mass index during pregnancy and pregnancy weeks) was performed to determine whether the intensity of LBP was associated with muscle activation.
Results: Among the participants, 9 women had LBP in STS motion (29.4±2.9 years, 34.6±1.9 weeks of pregnancy). The range of NRS score about LBP of them was 1-6 (Average score: 3.1±1.5). As the result of correlation analysis, no significant correlation between RMS-MT and NRS score was observed (r = 0.38，p = 0.32). On the other hand, significant positive correlation was observed between DRMS-MT-stand and NRS score (r = 0.74，p = 0.02). Additionally, this correlation was still statistically significant after adjustment for other factors related to LBP (β= 0.919, p = 0.02).
Conclusion(s): A positive correlation between the DRMS-MT-stand and the intensity of LBP was observed to be significant in spite of no significant correlation was observed in RMS-MT. From these results, greater ES muscle activation in STS motion compared with rest position might indicate a higher relationship with LBP during pregnancy.
Implications: For the management of LBP in STS motion during pregnancy, the assessment and approach to muscle activation during motion and also rest position might be effective. This relationship might be applicable to other motions that related LBP.
Keywords: Pregnancy, Low back pain, Biomechanics
Funding acknowledgements: This study was supported by JSPS KAKENHI (JP18H05962) and JKA promotion funds from KEIRIN RACE (28-143).
Topic: Musculoskeletal: spine; Musculoskeletal; Women's & men's pelvic health
Ethics approval required: Yes
Institution: Kishokai medical corporation
Ethics committee: Ethics Committee of Kishokai medical corporation
Ethics number: 2015_02
All authors, affiliations and abstracts have been published as submitted.
