Reijo Koskelo, Osmo Hänninen ja Risto Pohjolainen
Kuopio University, Department of Physiology, 1.1.1999–30.11.2001
The function responses of upper secondary school students in relation to the saddle chair and the adjustable table
The object of the study was to determine whether there are differences in the muscular system load when using either a saddle chair and an adjustable table or a conventional chair and table as workstations for upper secondary school students. Do the students feel they benefit from the adjustable workstation? Do the adjustable chairs and tables help to correct the students’ erroneous postures and do they benefit the students, schoolwork and the school?
The study was carried out in the Finnish upper secondary schools of Rautalampi and Suonenjoki. The test persons included 16 girls and 14 boys of approximately 18 years of age. The students in Rautalampi used saddle chairs and new adjustable tables. The students in Suonenjoki used conventional chairs and tables.
The comparison was made between
- a normal, conventional school chair, without the possibility of adjustment
- a normal, conventional school table, without the possibility of adjustment
- a saddle chair with wheels (Salli Saddle Chair) and height adjustment
- an adjustable table (Martela) with height and tilt adjustment according to the person's height
Myoelectric activity was measured with an averaged electromyography (EMG). The muscle tension of the test persons’ lower part of the trapezius and the L1-2 erectors of the back were measured using disposable bipolar surface electrodes. A digital camera was used to measure kyphosis, lordosis and scoliosis. The students also filled in a questionnaire about their state of health.
Disorders: During the two months prior to the inquiry, 23 out of 30 students had suffered from pain in the neck and shoulder area and 19 out of 30 complained about headaches. There were neither differences between the sexes nor the schools. During the follow-up, the problems in the neck and shoulder area were significantly reduced in Rautalampi students; in Suonenjoki, the problems reduced to a lesser scale. The subjective estimate of the headaches and lower back pains had reduced among Rautalampi students during the 24-month follow-up, but this was not statistically significant. Among Suonenjoki students, the headaches and lower back pains did not decrease.
Emg: The muscle tension of the Rautalampi students' trapezius and L1-2 muscles reduced statistically significantly (p<0.01). In Suonenjoki, the tension in the students' trapezius and erectors remained almost the same. However, the tension in the L1-2 muscles increased significantly (p>0.01) during the follow-up.
Kyphosis and lordosis: The mean average of Rautalampi students' kyphosis of the thoracic spine when standing at attention was 44.2 degrees in the initial measurement. After the 24-month follow-up, it was statistically significantly less, 30.13 degrees (p-value 0.000). The mean average of Suonenjoki students' kyphosis of the thoracic spine was 41.13 degrees in the initial measurement and after the 24-month follow-up it was less, 37.92 degrees. Rautalampi students' lordosis of the lumbar spine was first 37.47 degrees and finally 25.73 degrees, which is statistically significant. In Suonenjoki, the students’ lordosis was first 37.13 degrees and was reduced significantly to 32.52 degrees (p-value 0.024).
Scoliosis: In the initial measurements, the scoliosis of Rautalampi students was 92.12 degrees and after the 24-month follow-up it was significantly less, 90.22 degrees (p-value 0.000). The result shows statistically very significant changes to the good. On the other hand, the scoliosis of Suonenjoki students was 90.30 degrees in the initial measurements and 90.57 degrees in the final measurements. There were no significant changes.
Scoliosis occurred most often on the thoracic spine than anywhere else in the spine.
The students of Rautalampi upper secondary school who used intervention furniture received better grades in languages and in mathematics than Suonenjoki students, as seen in the table below.
|Intervention group (n=15)||Control group (n=15)|
|Elementery school||High school||P||Elementery school||High school||P|
|Science in all||8.8||8.2||<0.001||8.3||7.2||<0.001|
(Koskelo, Vuorikari, Hänninen 2007. Sitting and standing postures are corrected by adjustable furniture with lowered muscle tension in high-school students.)
In the table there are the grades of intervention (n=15) and control (n=15) groups of high school students, showing the change of averages between different schools and groups in languages, mathematics and marks in science topics with the statistical significance (P-value). The better grades in the intervention group can possibly be associated with the more comfortable school furniture and the reduction of neck and shoulder problems.
During the 24-month follow-up, there has been an improvement in the postural anomalies and in the posture of Rautalampi students. Muscular tension reduced among the students using height-adjustable saddle chairs and height and tilt-adjustable tables compared to students using conventional furniture. They also received better grades than the control group.
The workstation's adjustability significantly improves the ergonomics of schoolwork. The research results are of great importance for designing student workstations that are ergonomically designed and allow the students to work without any back pains or neck and shoulder area problems.