טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSadai Eri Pierre
SubjectDesign of a Sitting Supportive Device and Evaluation of its
Effect on Muscle Activity and Mean Heart Rate
Based on Two Sitting Sessions on a Long
Haul Aircraft Seat
DepartmentDepartment of Architecture and Town Planning
Supervisor Professor Issachar Gilad
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Objective: The purpose of this paper is to evaluate whether the proposed design of a postural support device can potentially ease trunk muscle strain where prolonged sitting is involved. A supportive device was specially designed to allow maintaining a more balanced and straight up posture with less effort while sitting on a commercial aircraft seat. 

Background:  Sitting for long periods in conjunction with unbalanced postures are both identified as major risk factors for low back pain. Various attempts to overcome this obstacle by postural supportive accessories have been investigated in the past. This study presents an additional ergonomic solution for prolonged sitting.

Method: Prolonged sitting activity was simulated by periodical sitting during which 20 minute sessions were analyzed in detailed subjects. 13 participants (mean age: 48.5) were asked to sit on a commercial aircraft seat during two consecutive 20 minute sessions. In one session, participants were asked to maintain a regular erect sitting posture; in the other session, the same task was performed with an additional trunk / pelvic supportive device. Surface electromyography signals were recorded from three muscle pairs: upper Trapezius (UT), T-9 level Erector Spinae (ES), and Latissimus Dorsi (LD); mean heart rate (MHR) was synchronically measured with a blood volume pulse (BVP) sensor. Mean integrated SEMG (IEMG) values were calculated for each muscle; average muscle activity (AMA) was calculated for each participant and compared across both sessions. MHR was compared for each subject in the same manner.

Results: AMA was significantly decreased while using the supportive device

(p = 0.001). A significant difference (p = 0.039) was found between left and right trunk muscle's activity in the regular posture. No significant difference was found in the supported posture. Both ES and LD muscle couples had significant activity level differences between both postures (respectively p = 0.001, p = 0.004) among the three measured pairs, ES having the highest one. Conversely to the AMA trend, a general (though statistically insignificant) increase in MHR level was detected in 77% of subjects during the same tasks.

Conclusions: Using the supportive device resulted in significantly decreased postural muscular effort, a more symmetrically balanced muscular activation and a possible reduction of the rate of muscular fatigue buildup. Further research concerning postural, respiratory, cardiac and hemodynamic parameters is warranted.