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J Acupunct Res > Volume 31(1); 2014 > Article
Ahn, Kim, Youn, Lee, Shin, Kim, Park, and Park: Test-retest Reliability and Intratest Repeatability of Measuring Lumbar Range of Motion Using Inertial Measurement Unit※
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Objectives :

The purpose of this study is to estimate the test-retest reliability and the intratest repeatability in measuring the lumbar range of motion of healthy volunteers with wireless microelectromechanical system inertial measurement unit(MEMS-IMU) system and to discuss the feasibility of this system in the clinical setting to evaluate the lumbar spine movement.

Methods :

19 healthy male volunteers were participated, who got under 21 points at oswestry disability index(ODI) were adopted. Their lumbar motion were measured with IMU twice in consecutive an hour for the test-retest reliability study. Intratest repeatability was calculated in the two tests separately. The calculated intraclass correlation coefficients(ICC) were discussed and compared with the those of the previous studies.

Results :

Lumbar range of motion of flexion 41.45°, extension 16.34°, right lateral bending 16.41° left lateral bending 13.63° right rotation −2.47°, left rotation −0.61°. ICCs were 0.96∼1.00(intratest repeatability) and 0.61∼0.92(test-retest reliability).

Conclusion :

This study shows that MEMS-IMU system demonstrates a high test-retest reliability and intratest repeatability by calculated intraclass correlation coefficients. The results of this study represents that wireless inertial sensor measurement system has portable and economical efficiency. By MEMS-IMU system, we can measures lumbar range of motion and analyze lumbar motion effectively.


This study was supported by a grant of the Korean Health Technology R & D Project(HI13C0510) Ministry of Health & Welfare, Republic of Korea

Fig. 1.
Depicts the flow chart for the method of a study based on a report of the average lumbar range of motion of 19 healthy volunteers with microelectromechanical system inertial measurement unit
Fig. 2.
Microelectromechanical system inertial measurement unit transmitter
Fig. 3.
Photograph of 2 microelectromechanical system inertial measurement unit transmitters attachment locations
L1 spinous process and between posterior superior iliac spine.
Fig. 4.
A screenshot of basic posture, flexion, extension, right lateral bending, left lateral bending and right rotation movement from the sample movie
Fig. 5.
A sample graph of a lumbar flexion movement
Green line symbolizes lumbar flexion movement. Each volunteer performed the flexion movement 3 times.
Fig. 6.
A sample graph of a lumbar extension movement
Blue line symbolizes a lumbar extension movement.
Each volunteer performed the extension movement 3 times.
Fig. 7.
A sample graph of a right lateral bending movement of lumbar
Red line symbolizes right lateral bending movement.
Each volunteer performed the right lateral bending movement 3 times.
Fig. 8.
A sample graph of right rotation movement of lumbar. Orange line symbolizes right rotation movement. Each volunteer performed the right rotation movement 3 times
Table 1.
Evaluation Circumstances
Space Indoor space(5×5 m)
Environment 2 microelectromechanical system inertial measurement unit transmitters
1 radio frequency receiver
1 computer with LabVIEW to receive data
1 computer for watching a sample movie
1 pair of slippers
1 pair of trousers
2 staff members 1 staff for information process
1 staff for attachment transmitters to subjects and alignment motion of subjects
Aid for assessment tool Oswestry disability index questionnaire
A sample movie (basic posture, flexion, extension, lateral bending and rotation)
A script of verbal order
Table 2.
Lumbar Range of Motion and Reliability
Motion First Experiment Second Experiment Comparison between the first experiment and second experiment
M (SD) ICC (2,1)a 95 % CI M (SD) ICC (2,1)a 95 % CI M (SD) ICC (2,2)b 95 % CI
Flexion 41.75 (7.70) 1.00 0.99∼1.00 41.15 (8.33) 1.00 1.00–1.00 41.45 (7.92) 0.71 0.24∼0.89
Extension −15.40 (6.26) 0.99 0.97∼1.00 −17.28 (7.66) 0.99 0.98–1.00 −16.34 (7.03) 0.61 0.00∼0.85
Right Bending 16.39 (3.14) 0.96 0.89∼0.98 16.42 (3.72) 0.95 0.86–0.98 16.41 (3.36) 0.84 0.58∼0.94
Left Bending −13.67 (3.99) 0.99 0.99∼1.00 −13.60 (3.65) 0.99 0.96–0.99 −13.63 (3.81) 0.90 0.73∼0.96
Right Rotation −2.93 (3.06) 0.98 0.95∼0.99 −2.00 (3.98) 0.97 0.92–0.99 −2.47 (3.53) 0.92 0.77∼0.97
Left Rotation 0.04 (3.92) 0.95 0.88∼0.98 −1.27 (4.51) 0.97 0.91–0.99 −0.61 (4.19) 0.87 0.65∼0.95

M : mean(°). SD: standard deviation(°).

ICC : intraclass correlation coefficient. CI: confidence interval.

a intratest repeatability, ICC(2,1), agreement.

b test-retest reliability between 1 hour, ICC(2,2), agreement.

The second experiment was carried out after 1 hour.

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