• Safety and Health at Work
• /
• v.6 no.3
• /
• pp.206-210
• /
• 2015

Background: Fatigue has a strong impact on workers' performance and safety, but expedient methods for assessing fatigue on the job are not yet available. Studies discuss posturography as an indicator of fatigue, but further evidence for its use in the workplace is needed. The purpose of the study is to examine whether posturography is a suitable indicator of fatigue in clerical workers. Methods: Thirty-six employees (${\emptyset}$ 34.8 years, standard deviation = 12.5) participated in postural tasks (eyes open, eyes closed, arm swinging, and dual task) in the morning and afternoon. Position of their center of pressure (COP) was registered using a Nintendo Wii Balance Board and commercial software. From registered COP time series, we calculated the following parameters: path length (mm), velocity (mm/s), anterior-posterior variance (mm), mediolateral variance (mm), and confidence area ($mm^2$). These parameters were reduced to two orthogonal factors in a factor analysis with varimax rotation. Results: Statistical analysis of the first factor (path length and velocity) showed a significant effect of time of day: COP moved along a shorter path at a lower velocity in the afternoon compared with that in the morning. There also was a significant effect of task, but no significant interaction. Conclusion: Data suggest that postural stability of clerical workers was comparable in the morning and afternoon, but COP movement was greater in the morning. Within the framework of dynamic systems theory, this could indicate that the postural system explored the state space in more detail, and thus was more ready to respond to unexpected perturbations in the morning.

• Journal of the Korean Society of Physical Medicine
• /
• v.15 no.2
• /
• pp.83-91
• /
• 2020

PURPOSE: Postural and structural asymmetry due to muscle imbalances around the lower back and pelvis are the causes of back pain. Muscle imbalances in patients with chronic low back pain affect the pelvic tilt and movement, and it is necessary to assess the pelvic movement ability using the appropriate tools to determine the mediating effects of lower back pain. This paper reports the reliability and validity of the Sensbalance Therapy Cushion (STC) for pelvic movement and proprioception. METHODS: In this study, the Wii balance board (WBB) was used as a golden standard for pelvic movement measurements. FABQ, KODI, Myovision, and Pelvic movement were measured in 50 patients with chronic low back pain. The correlation between the lower-back muscle activity and pelvic movement was checked. The pelvic movement parameter was measured twice to determine the intra-rater reliability. RESULTS: The STC showed high test-retest reliability in the pelvic tilt measurements (ICC = .672 - .809). The test-retest reliability of proprioception measurements (ICC = .588 - .859) and reaction time measurements (ICC = .542 - .836) were also high. The relationship between the WBB and STC showed a significant positive correlation with the pelvic tilt test (p < .01). The posterior pelvic tilt and lower-back muscle activity showed a significant negative correlation (p < .01). The pelvic left tilt and lower-back muscle activity showed a significant negative correlation (p < .05). CONCLUSION: The results revealed the high reliability and validity of the STC. Therefore, the STC can be used as an objective measuring device for evaluating pelvic tilt, proprioception, and reaction time in low back pain patients.

• Physical Therapy Rehabilitation Science
• /
• v.9 no.2
• /
• pp.74-81
• /
• 2020

Objective: To prevent low back pain, an objective evaluation tool to evaluate pelvic mobility and exercise to improve the flexibility of the lumbar region is needed. The purpose of this study was to compare the results of pelvic mobility measurements using the Wii Balance Board (WBB) and Sensbalance Therapy Cushion (STC), evaluate the usefulness of the STC as a tool for measuring pelvic mobility. Design: Cross-sectional study. Methods: Fifty healthy subjects participated in this study. The subjects performed pelvic mobility range, proprioception, reaction time and reach of the arm using the STC. The pelvic movement parameter was measured two times to determine the intra-rater reliability. To measure the correlation between lumbar muscle tension and pelvic mobility, Myovision was used to measure tension of L4, L5 level erector spinae muscle. Correlations between measured variables were checked to determine the validity of the pelvic mobility assessment tool. Results: STC showed high test-retest reliability in pelvic tilt measurement and reaching task [intraclass correlation coefficients (3,1)=0.804-0.915]. The relationship between WBB and STC showed a significant positive correlation with the pelvic tilt and reaching task (p<0.05). Posterior tilt and erector spinae activation (Lt. L5) showed a significant negative correlation (p<0.05). Left, right tilt and erector spinae activation (L5) showed a significant negative correlation (p<0.05). Conclusions: This study confirmed the advantages of the STC and found efficiency as an objective measuring device of pelvic mobility.

• Journal of Biomedical Engineering Research
• /
• v.42 no.5
• /
• pp.225-231
• /
• 2021

The purpose of this study was to investigate the effect on the activity of the upper trapezius and erector spinae according to the length difference of the backpack using electromyogram (EMG). We also conducted a study comparing the center of pressure (COP) and weight distribution before and after using Wii® balance board. Thirty individuals were randomly assigned to the experimental group (n=14) wearing a backpack with a short right strap length and a control group (n=16) wearing a backpack with the same strap length. Data were collected by dividing into groups, carring a 15% weight backpack and walking for 20 minutes on a treadmill. As a result of analyzing the EMG data, there was no significant change in the upper extremity muscle activity of the control group, but it was significantly decreased in the right upper trapezius activity of the experimental group (p<0.05). In addition, there was a significant change of COP in the experimental group (p<0.05), but there was no significant difference of the weight distribution in both groups. Recognizing mechanical changes in the body that may occur due to the asymmetry of the strap length is thought to be helpful for systematic ergonomic intervention according to changes in the external environment in the future.