Ryuichi ITO i.ryuuichi@gmail Production Engineering of Advanced Engineering Course

1. On the Cause of Experienced Care Workers’ Lower Back Pain:Considering Posture and the Strength of Back Muscle RyuichiITO i.ryuuichi@gmail.com Production Engineering of Advanced Engineering Course Niihama National College of Technology Japan-Taiwan symposium In 2012, In Taiwan

2. Background In Japan, 70 ％ of people in the care workers have complained of lower back pain. but • People who are involved in care workers for many years is not that always cause lower back pain. • Some care workers continue to work • even if they have lower back pain. • In other words: • There are points unlikely to be lower back pain.

3. Experimental Method Examinee（18 pairs in total） • Care workers, and students of college of welfare make 9 pairs within each group. Patient（1 person） • We assumed patient who requires full support. • Bathing care by two-persons • She is female student who is weight about 48 kg. After the experiment, the patient evaluates the care level of comfort in five point scales.

4. Three-Dimensional Motion Analysis System 20 points in total Infrared marker front back Infrared camera Model of marker

5. Operation of Bathing Services From edge of bathtub to bottom of bathtub From wheelchair to edge of bathtub There are four patterns. Task1 Task2 from bottom of bathtub to edge of bathtub from edge of bathtub to wheelchair Task3 Task4

6. The Patient Evaluates the Care Level of Comfort in Five Point Scales Excellent group Fair group Middle group

7. Definition of Waist Angle (θ) neck vertical direction model of waist angle θ waist

8. Moment Round the Waist of Care Worker Ｌg F・ＬS・Sin(θ) F WP・ＬS・Sin(θ) θ‘ θ ＬS WC L WP WC・Ｌg・Sin（θ’）　 （θ）

9. Strengthof back muscle : Fnecessary in caring posture Moment of F＞　 Moment of WP＋　Moment of WC F＞ WP+0.3・W c total F・ＬS・　　　　 ＞WP・ＬS・+ WC・Ｌg・ Sin（θ） Sin（θ） Sin（θ） LS / LS F　　　＞ WP・+ WC・Lg/LS H=height LS＝0.28・H Lg＝0.14・H WC=0.6・W c total F＞　WP+0.6・W c total・（0.14H）/（0.28H）

10. Assuming as follows; • F ＞ WP + 0.3 ・ WC Care worker : weight is 60 (kg) Patient : weight is 50 (kg) F : Strength of back muscle F > 50 + 0.3 ・ 60 = 68 (kg) If strength of back muscle of him is value less than 70 (kg), he has higher risk of lower back pain.

11. Definition of Roundness of the back (τ) back1 back2 τ waist Model of roundness of the back

12. Correlation Diagram of Strength of Back Muscle and Roundness of the Back Strength of Back Muscle [kgf]

13. Conclusion • The risk of the lower back pain increases. 1. When expert care workers’ strength of back muscle is less than “Wp+0.3*Wc”, even if he has not had lower back pain. 2. When care workers have the posture of large roundness of the back.