New Ways of Measuring Farmers' Posture at Work

Kyo KOBAYASHI, National Agricultural Research Center, Japan, 2003-12-01

Twency years ago, it was common to see old people in rural areas bending over as they worked in the field. It is a rare sight in Japan today. Changing life-styles, and the spread of rice transplanters and herbicides, have changed the nature of field work. Farmers no longer have to bend over to plant and weed rice. However, they still have to bend over to cultivate vegetables. Compared to rice production, there has not been much mechanization of vegetable production.

Various methods are used to record work posture. With regard to farm work, most measurements are made in writing, or by recording workers with a video camera for later analysis. Motion analyzers are used to record the movements of athletes, but analyzing the data takes a great deal of time. We have developed a portable device, the "Work Posture Monitor", which can continuously record the posture of farmers at work in the field.

The Work Posture Monitor

This consists of inclination sensors, sensor mounts, a digital memory (for logging data) and data analysis software, as shown in Fig. 1. Work posture is measured according to the angle of each part of the subject's body (trunk, arms, legs etc.) in relation to an axis perpendicular to the ground.

The sensors are attached to the subject's body by flexible straps. The standard places to which the sensors are attached are the outside of the ankle, the outside of the thigh, the trunk and the upper arm.

The coordinates of each body point are calculated, and connected in a straight line to form a stick figure (Figs. 2 and 4). In this way, we are able to define ten work postures, ranging from standing upright to sharply bent forward. ?

The Work Posture Monitor can also record how long growers spend in the various postures. For example, it can show what percentage of his working time the grower spends bending over.

Work Posture in the Transplanting of Sweet Potato

Fig. 2 shows the results when the monitor is used to record the manual transplanting of sweet potato seedlings. Each little stick figure represents an interval of one second. The stick figures show the progress of the work, from the lower right to the upper left. Fig. 4 shows the posture of the grower when the transplanting procedure is mechanized.

In the case of the manual transplanting of sweet potato seedlings, the grower spends 95% of his time sharply bent over at an angle of more than 30 degrees (Fig. 3). In contrast, when the transplanting is mechanized, the grower spends most of his time sitting down. (The intervals spent standing represent the times he has to turn the machine around at each end of the field). Less than 10% of his time at work is spent bending over.

Use of the Monitor

The Work Posture Monitor has been used at an agricultural extension center, a research institute and a university. We are continuing to develop simpler methods of evaluating the postures which farmers have to adopt when they are at work in their fields. The results will be used to help create a safer and more comfortable working environment on farms, and help farmers avoid occupational injuries.

Index of Images

• 

  Figure 1 Diagram of the Work Posture Monitor

• 

  Figure 2 Work Posture during Transplanting of Sweetpotato (Red Line = Manual, Blue Line = Mechanized).

• 

  Figure 3 Recorded Work Posture during Manual Transplanting of Sweet Potato

• 

  Figure 4 Recorded Work Posture during Semi-Mechanized Transplanting of Sweet Potato, Using Power Tiller