Iranian Journal of Ergonomics

Due to the rapid growth of metropolitan areas and the lack of public transport within the city today, many people are traveling in a standing position when using these vehicles, including buses. Surveys show that most non-accidental injuries to passengers on public transport occur in a standing position (8). The results show that in the short period of the first 35 minutes, between the three modes, sitting, standing and standing-sitting, the least fatigue was related to standing-sitting (11). Since the average time for an inter-city commute is less than 35 minutes (12); the purpose of this study was to perform an ergonomic evaluation of the standing-seating area for commuters on the intercity busses.

 

The present study was a descriptive-analytical and experimental study on 8 young men with a mean age of 25.25 (SD). This research was approved by the Ethics Committee of Tehran University of Medical Sciences (Code: IR.TUMS.SPH.REC.1397.076). In order to evaluate the ergonomic status of the standing-seated seat and to compare it with the standing position of the passengers, the model intercity bus (Benz 457) was used. For this purpose, electromyography and Borg scale were used for ergonomic evaluation of both conditions, respectively. Initially, the idea of ​​using a standing-sitting seat for public transport within the country's intellectual property center was registered at 97732. The dimensions of the seat surface are shown in Figure 1.
 

Figure 1. Standing-sitting seat designed specifically for intercity public transport (A: open mode; B: folded mode).

Figure 2 shows the status of the participants on the intercity bus. The bus traffic scenario consists of a 30 second interval, performed for everyone on a smooth, non-traffic road. The UK's DataLOG MWX8 Surface Electromyography (Biometrics Ltd) was used to measure the level of contractile activity of the leg muscles. For this purpose, the target muscles were first identified according to previous studies (9,14-16), and finally two muscles (internal twin and sole) were selected for recording electromyographic data. Prior to the start of the defined scenario, maximal voluntary contraction (MVC) was recorded for all participants’ target muscles separately by electromyographs using existing protocols (18). Each condition was repeated 3 times for each individual and each time the EMG signals were recorded. Then, the perceived feeling of discomfort was recorded after 15 minutes of using the standing-sitting seat using 10-point Borg scale for shoulder, arm, forearm, hand, waist, hip, thigh, leg, foot, and whole body.
 

Figure 2. Situation of participants in the intercity bus (right: standing, left: standing-sitting).

The results showed that in the whole body and all organs except for the buttock, perceived discomfort in the standing posture was higher than in the standing /sitting posture (Figure 3).
According to Table 2, the level of contractile activity of both the left and right leg muscles in the standing-sitting position was significantly lower than in the standing position.
 

Figure 3. Comparison of perceived discomfort in standing and standing-sitting positions (* = (P<0.05)).

Table 2. Results of muscle contraction activity in standing and standing-sitting position.

The results show that in both standing and sitting-position the soleus muscle had more contractile activity than the internal gastrocnemius muscle. Figure 4 shows the electromyographic signal of the soleus muscle over time in both standing and standing-sitting positions.
 

Figure 4. Electromyographic signal of right and left soleus muscles in two standing and standing/sitting modes in three intervals of acceleration, steady speed and deceleration of intercity bus.

Previous studies have reported an increased sense of discomfort in a standing/sitting position compared to a standing position (11,23,24). One of the most important reasons for commuters' standing travel on busy city buses is space constraints (5). It is notable that, the saddle like seats due to its small size compared to the seats on the city bus needs little space. Although previous research confirms the improvement of lower extremity and whole body discomfort when using standing-sitting chair compared to standing posture (11,25); however, studying the upper and lower limbs show that sitting-chair use in relation to posture standing had no effect on the discomfort of these organs and in some cases even increased discomfort (11,23), which contradicts the findings of the present study. One reason for this contradiction is that the standing-sitting seats for the bus has completely eliminated the activity of getting the balance handle, and passengers travel without any activity on the upper limbs.
Although no studies have been reported on the use of standing-seating to control foot area stress in intercity public transport, the findings of the present study are consistent with the results of various studies aimed at improving working conditions using standing-seating (11,23-25,27).
Studies on the effect of standing-sitting chair on standing posture have shown that contractile activity of the internal gastrocnemius and soleus muscles decreased in standing-sitting position (24). In this study, as in the present study, in addition to the type of selective muscle, the results of comparing the muscular activity of the two states were similar. The only difference between these two studies is the placement of standing-sitting chairs, as the study aforementioned studies the use of standing-sitting chairs for occupations with long standing. However, in the present study, the use of standing-sitting seats for commuters on the intercity bus has been considered.

According to the findings, this chair was able to improve the standing position of passengers by reducing the contraction of the leg muscles and improving the discomfort of different body parts except for the hips. Therefore, the seated seating area for in-car public transport can be used as a suitable tool in all intercity public transport services including the subway, rapid bus transports, and bus to improve the ergonomic conditions of standing passengers.
 

The authors thank all those who helped them writing this article.

 

The authors declared that there are no conflicts of interest.