Postural system based on Inertial sensors to analyse and correct the. posture (Profiler ): A validation study.

Transcription

1 Postural system based on Inertial sensors to analyse and correct the posture (Profiler ): A validation study. INTRODUCTION. In developed countries, the workers percentage who spend more than 75% of their time work in a sitting is grown exponentially in the last 50 years. This is due to the introduction of computers as an indispensable tool for work development. (Bennie et al. 2015, Russell et al. 2015). One of the aspects with greatest impact on musculoskeletal problems development is to maintain a non-ergonomic sitting for a long time. (O sullivan et al. 2012). In order to correct the wrong, it is necessary be aware and modify it to achieve the ergonomic. In different areas of applied medicine, it is promoted the parameterization and the instrumentalization through inertial sensors to record the and the movement during the performance of standardized functional tests. These tests measure patients health status to establish and implement effective treatment strategies. (Cuesta-Vargas et al 2010; Kavanagh et al 2008). Inertial sensors are instruments able to collect kinematic variables of any gesture or movement due to its size, portability and reliability (Gebruers et al 2010; Giggins et al 2013). Therefore, inertial sensors have been used both in clinical practice and in laboratory as a feedback tool for balance and ambulation tests (Gebruers et al. 2010; Mancini et al 2012). To take advantage of the gained experience in the use of inertial sensors and to improve the people ergonomics who remain seated for a long time, the device

2 Profiler is designed. It is a system that integrates the signal of two inertial sensors to monitor the subject and alert when he/she acquires an incorrect. This warning does not stop until the subject is placed again in a correct. The requirement of high quality data is as important for clinical trial as randomization, blindness, etc. Some of the consequences of unreliable measurements are: increased sample, biased estimates, etc. (Fleiss 1986). The aim of this study is to analyze the reliability and external validity of the Profiler as instrument to measure kinematic variables during the acquisition of static s and the development of back movements. The hypothesis of this study is that the Profiler reliability and external validity range from good to excellent to measure kinematic variables during the acquisition of static s and the development of back movements. MATERIAL AND METHODS Twenty seven healthy young adults (12 men and 15 women) participated in this cross-sectional study of repeated measure. Participants were students and staff from the Vrije Universiteit Brussel. Data were collected between November and January The exclusion criteria used were: younger than 18 or older than 40 years old, to be pregnant, surgical intervention on lower limbs or spine within the 12 months before with the recruitment and neuro-

3 musculoskeletal or cognitive limitation from any ethiologhy that impede to complet the protocol. All the participants gave the informed consent signed before starting the protocol. The study complied with the principles laid out in the Declaration of Helsinki. Personal data of the participants were treated in accordance with the Spanish Organic Law of Protection for Personal Data 15/1999. Profiler Profiler (IntoPhysio BVBA, Belgium) is a system designed to be used as Inertial Sensor Real-Time Feedback System (ISRTFS). It consists of two inertial sensors which kinematic data are integrated into a central unit (figure 1). The maximum sampling frequency is 20 Hz. Zebris Ultrasound System To analyze the Profiler validity, Zebris Ultrasound System (Jaw Motion Analyzer, Zebris Medical GmbH, Isny, Germany) was used. This instrument has a sampling frequency of 200 Hz and in previous studies has demonstrated the reproduction accuracy of less than 0.1 angles to the main movement components and components coupled to 0.2º (Cattrysse et al. 2009). Procedure Both devices were placed in the centre of the back, on the longitudinal axis of the spine. A triangle was placed at the line height which joins the two lower angles of

4 the shoulder blades, while the second one was placed on the spine at the level of L5-S1 (Figure 3) line which join the postero-upper iliac spines. Each participant was placed in standing looking straight ahead, relaxed and with the upper limbs parallel to the body. When a beep sounded, the participant remained static five seconds, then performed a trunk flexion until touching the front of the knees with palms. At this time, the participant returns to the starting and, once achieved, remained five seconds in a static. The participant should take four seconds to reach maximum trunk flexion and four seconds to recover the starting. This movement was repeated four times and the same protocol was performed three times for each participant. The entire measurement period was 14 days. Outcome variables obtained were: runtime, maximum angular displacement (degrees), maximum angular velocity ( / s), average angular velocity ( / s), maximum angular acceleration ( / s2), acceleration and angular average ( / s2). All outcome variables were analyzed at four different times: initial static, trunk flexion, initial recovery and final static. Statistical Analysis The statistical analysis of this study included a descriptive analysis of the sample with anthropometric mean values and the average value of outcome variables. "Intraseries" reliability analysis of the calculated measure from recorded values in each of the four repetitions performed in each series was performed. Addition, it was calculated "inter series" reliability from those recorded values in each of the three series made by each participant. Reliability was interpreted as keeping

5 the internal consistency of the measures and was calculated using an intraclass correlation coefficient (ICC; 2:1), together with the 95% confidence interval for each variable. Correlation values were categorized according to Shrout and Fleiss (1979): ICC<0.20 (very low correlation); 0.20<ICC<0.39 (low correlation); 0.40<ICC<0.69 (moderate correlation); 0.70<ICC<0.89 (high correlation); ICC>0.90 (Very high correlation). Criterion validity was analyzed through Pearson correlation index (r) which was calculated among the outcome variables obtained from Profiler and Zebris Ultrasound System. Correlation values were categorized according to the following scale: r<0.49 (poor), 0.50<r<0.74 (moderate), r>0.75 (strong). (Kamavuako et al. 2013; Shrout and Fleiss 1979). These calculations were performed using the Statistical Package for the Social Sciences (SPSS) (version 21.0 for Windows, Illinois, USA). RESULTS The present study involved 26 volunteers (14 women and 12 men) with a mean age of years, an average height of cm, weighing kg and with a mean body mass index of kg / m 2. Table 1 presents sample descriptive values divided by gender. On Table 2 is possible to observe the average values recorded during the four different kinematic moments considered in the present study. The results are presented in absolute values because the displacement that occurs in the

6 recovery of the initial (truck extension) has a negative sign, which determines that velocities and accelerations have also negative sign. The average value of the intraclass reliability was 0.983, showing the lower reliability in the variable "acceleration end During static " (ICC: 0.963), while the variable that present higher reliability was "displacement During initial static " (ICC: 0997). Similarly, the average value of the interseries reliability was 0.972, being the variable "acceleration during initial static " the one with lower reliability in the measurements (ICC: 0953), while the variable with higher reliability was "displacement during return to initial " (ICC: 0.987). Other reliability values intra and interseries can be observed in Table 3. The Pearson's correlation index can be observed in table 4. The average value of correlation was r = The variable "acceleration during return to initial " has the lower correlation rate (r = 0.952), while "displacement during trunk flexion" was the variable with the higher Pearson's correlation value (r=0.998). A graphical representation of a kinematic record collected during trunk flexion/extension is presented in Figure 1. DISCUSION The need for high quality data forces to analyze the reliability and validity of all instruments intended to be used as measurement, intervention and/or real-time feedback tools (Prieto et al. 1998). With the intention to optimize a Profiler future use as a tool to correct, in real time, bad workers postures maintained for long periods of time this study was designed to analyze the reliability and validity of Profiler as a tool for measuring kinematic variables for maintaining a static posture and during the development of trunk flexion/extensions. Once the results

7 were analyzed, observing reliability values that range from ICC=0.953 to ICC=0.997 (table 3) and with Pearson s correlation indexes (r) that range between r = and r = (table 4), could be possible to affirm that the study objective has been achieved and the hypothesis could be confirmed. According to the results presented in this study, the reliability of Profiler is excellent for recording kinematic variables both static s and during the development of movement, as categorized by Shrout and Fleiss (1979). These levels of reliability have been observed within intraseries measurements (repetitions performed at successive times), with values never lower than ICC = (acceleration during final static ) (table 3) values. Also, interseries reliability values (reliability calculated between a series and other) are slightly lower compared to those previously reported, but their levels of reliability were not descended from ICC = For its part, the external validity of Profiler, using Zebris Ultrasound System as a reference tool the gold standard, is strong (Kamavuako et al 2013;. Shrout and Fleiss 1979) due the values observed in the indices of correlation that in no case were lower than r = (acceleration during return to initial ). The results obtained in the present study can be used to justify the Profiler is an instrument that provides data with excellent reliability and a strong external validity for recording kinematics variables during both static and dynamic situations. Thus, the use of Profiler in the development of clinical trials as an intervention tool and / or to measure results guarantees that data obtained from this instrument to record the kinematic static and dynamic situations are high

8 quality, limiting the adverse consequences from the use of not appropriate instruments. LIMITS OF THE STUDY This study presents some limitations that must be taken into account in interpreting the results, as well as for the development of future studies. A limit is that only a static (stand ), and a trunk movement (flexion / extension) was analyzed. On the other hand, the Profiler was ed only on the back. Finally, all measurements were performed by a single researcher, so that future studies could analyze inter-observer reliability. CONCLUSION The main conclusion that can be reached after analyzing the results obtained in this study is that the Profiler is a reliable and valid instrument to record high quality kinematic variables during back static and dynamic situations.

9 REFERENCES Bennie JA, Pedisic Z, Timperio A, Crawford D, Dunstan D, Bauman A, van Uffelen J, Salmon J. Total and domain-specific sitting time among employees in desk-based work settings in Australia. Aust N Z J Public Health Jun;39(3): doi: / Cattrysse E, Provyn S, Kool P, Gagey O, Clarys JP, Van Roy P. Reproducibility of kinematic motion coupling parameters during manual upper cervical axial rotation mobilization: a 3-dimensional in vitro study of the atlanto-axial joint. J Electromyogr Kinesiol 2009;19(1):93e104. Cuesta-Vargas AI, Galan-Mercant A, Williams JM. The use of inertial sensors system for human motion analysis. Phys Ther Rev Dec;15(6): Fleiss JF. The design and analysis of clinical experiments. John Wiley & Sons. Inc., New York, NY, USA Gebruers N, Vanroy C, Truijen S, Engelborghs S, De Deyn PP. Monitoring of Physical Activity After Stroke: A Systematic Review of Accelerometry-Based Measures. Arch Phys Med Rehabil Feb 1;91(2): Giggins OM, Persson UM, Caulfield B. Biofeedback in rehabilitation. J NeuroEngineering Rehabil Jun 18;10:60. Kamavuako EN, Rosenvang JC, Horup R, Jensen W, Farina D, Englehart KB. Surface versus untargeted intramuscular EMG based classification of simultaneous and dynamically changing movements. IEEE Trans Neural Syst Rehabil Eng. 2013; doi: /TNSRE

10 Kavanagh JJ, Menz HB. Accelerometry: A technique for quantifying movement patterns during walking. Gait Posture Jul;28(1):1 15. O Sullivan K, O Sullivan P, O Sullivan L, Dankaerts W. What do physiotherapists consider to be the best sitting spinal posture? Manual Therapy 2012;17(5):432e7. Mancini M, Salarian A, Carlson-Kuhta P, Zampieri C, King L, Chiari L, et al. ISway: a sensitive, valid and reliable measure of postural control. J NeuroEngineering Rehabil Aug 22;9:59. Prieto L, Lamarca R, Casado A. [Assessment of the reliability of clinical findings: the intraclass correlation coefficient]. Med Clin (Barc) Feb 7;110(4): Russell BA, Summers MJ, Tranent PJ, Palmer MA, Cooley PD, Pedersen SJ. A randomised control trial of the cognitive effects of working in a seated as opposed to a standing in office workers. Ergonomics Oct 22:1-8. Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol Bull. 1979;86(2):

11 TABLES Female Male Age (years) Weight (Kg) Height (m) Body Mass Index (Kg/m 2 ) N Table 1: Description variables of the participants.

12 Initial static Trunk flexion Return to initial Final static Time (s) 4.96 (±0.28) 4.18 (±0.17) 4.11 (±0.21) 5.03 (±0.09) Displacement (º) Max (±0.38) Velocity (º/s) Aceleration (º/s 2 ) Mean (±2.04) Max (±3.18) Mean (±1.19) (±6.44) (±1.91) (±2.86) 5.07 (±0.83) (±7.37) (±2.14) (±4.77) 5.35 (±0.90) 3.11 (±1.25) (±4.21) (±3.51) (±4.33) Max (±2.00) (±3.19) (±0.84) (±4.94) Table 2: Mean values of the results variables divided by four independent recording periods.

13 Displacement (º) Velocity (º/s) Initial static Trunk flexion Return to initial Final static Intraserie Interserie Intraserie Interserie Acceleration (º/s 2 ) Intraserie Interserie Table 3: intraserie and interserie reliability (ICC) measures divided by different s and movements measured..

14 Initial static Trunk flexion Return to initial Final static Displacement (º) Max Velocity (º/s) Mean Max Mean Aceleration (º/s 2 ) Max Table 4: Profiler External validity measurement correlated with Zebris Ultraound system.

15 FIGURE