Using ergonomics principles to help Nicaraguan coffee harvesters

Coffee is second to oil in commodity trading. In recent decades, there has been a rapid proliferation of different coffee certification initiatives seeking to advance environmentally friendly and socially responsible systems of coffee production and trade. Fair Trade, for example, is a certification scheme that attempts to build an alternative trade network between the global North and South by linking socially and environmentally conscious consumers in the North with disadvantaged producers in the South engaged in socially and environmentally sustainable agriculture. While Fair Trade has promoted premiums for social development of participating coffee producers and strengthened the institutional capacities of the cooperatives involved, studies have shown that its ability to significantly enhance the work conditions of coffee laborers remains limited.

Since it came to Nicaragua in the mid 1800s, coffee farming has played a significant role in Nicaragua's economy and environment. More than 40,000 families are involved in coffee farming and provide the equivalent of 280,000 permanent agricultural jobs. However, Nicaragua still remains one of the poorest countries in the world (the 2nd poorest country in the Western Hemisphere). While ergonomics has been widely applied in many industrially developed countries in designing better methods and tools to improve work conditions and productivity, this common practice is still scarce among Nicaraguan coffee farms. One of the reasons for the lack of ergonomics applications in Nicaragua is probably the lack of trained ergonomics practitioners.


This illustrates Picking coffee cherries using a large harvesting basket
Picking coffee cherries using a
large harvesting basket
This illustrates Picking coffee cherries using a small basket
Picking coffee cherries using a
small basket
This illustrates Picking coffee cherries using a newly developed harvesting bag
Picking coffee cherries using a
newly developed harvesting bag

One of our research collaborators, Ms. Kate Stewart spent some time in Nicaragua and noticed that the harvesting baskets used by most coffee harvesters are awkward. A quick biomechanical analysis of this basket identified a few problems that may cause discomfort and injuries to the harvesting workers. In order to reduce the biomechanical load on the workers, she developed a harvester's bag. The present study was then launched to compare the newly developed prototype bag with conventionally used baskets in coffee harvesting activities. Additionally, the study goals were to:

  • Implement a participatory ergonomics intervention among Nicaraguan coffee harvesting workers to improve their work conditions,
  • Use the ergonomics application as a showcase to conduct ergonomics studies in developing countries and demonstrate that simple solutions can make a difference in terms of improving work conditions, and
  • Involve local Nicaraguan researchers in the project so that they can gain practical experience in ergonomics research and application.

How was this study done?

Two harvesting baskets (small and large) and the newly designed bag were compared during various coffee harvesting tasks in order to evaluate their physical impacts on the harvesting workers. Coffee harvesting jobs include the following major tasks:

  • Coffee cherry picking: On slightly different terrains, workers use both hands symmetrically at different heights of coffee bushes and place the cherries into the basket/bag,
  • Walking with full basket/bag: When the basket/bag is full, the worker walks to the location where he/she had placed a large sack
  • Dumping coffee cherries into a large sack: The worker dumps the coffee cherries from the basket/bag into the sack and walks back to pick coffee cherries again.
  • Lifting and carrying the large sack: At the end of the day, workers lift the large sacks and carry them down the hill to be processed. The large sack was usually filled up by the end of a shift (up to almost 120 lbs).



This illustrates Worker dumps full basket to a large sack.
Worker dumps full basket
to a large sack.
This illustrates Lift and carry a full large sack at the end of day
Lift and carry a full large sack
at the end of day
This illustrates Walking with a full basket
Walking with a full basket

The baskets/bag physical impacts on the workers are estimated by two methods:

  • Measuring 4 muscle load on the shoulder and low back regions during the 4 major tasks when the baskets/bag are used
  • Worker's self-report on body discomfort and opinions on the equipment used.
This illustrates Field EMG data collection to measure muscle activities
Field EMG data collection to measure muscle activities

The muscle loads were measured with surface electromyography (EMG) techniques during the different tasks. Small electrodes were attached to the surface of 3 shoulder muscles (2 on the top of the shoulders – responsible for lifting the upper arms, and one on the shoulder scapula bone – responsible for right upper arm rotation and lifting up to the side) and one low back muscle. Muscle activities during the different coffee harvesting tasks using the different equipment were measured and transmitted telemetrically to a laptop computer where the signals were recorded and stored. These recordings were later analyzed in the laboratory.

A "Muscle Aches and Pains Symptoms Survey" was distributed to workers to obtain information about aches or pain levels when different equipment was used as well as their opinions about the equipment.
Three Nicaraguan researchers assisted with this study. This also provided them with opportunities to have hands-on experience in conducting ergonomics field research.

Who were involved in this study?


This illustrates Nineteen coffee harvesting workers from 2 coffee farms in Northern Nicaragua participated in this study.
Nineteen coffee harvesting workers from 2 coffee farms in Northern Nicaragua participated in this study.

Nineteen harvesting workers from two coffee farms in Northern Nicaragua participated in this study. The coffee harvesting is mainly a male dominant occupation. Only two female subjects were included in this study. The participants were informed about this study by the Nicaraguan researchers who spoke Spanish.

What did we find?

Based on the survey, some workers felt more comfortable with the new bag, but others still preferred the small basket. However, in general, the large basket was considered very uncomfortable. Most workers reported that the bag did not hurt their back as much as compared to the baskets. This seems to reflect the original design idea of the bag, which was to reduce the loading on the low back that the old large basket caused. Some complained that the bag was too big and some also commented that the bag was uncomfortable during walking. These comments indicate that there are some usability issues with the bag design that might have not been adequately considered when it was developed.
During the coffee cheery picking task, no significant differences were found for most of the shoulder and low back muscle loadings between the three pieces of equipment. These findings were consistent with the worker reported discomfort results. No significant differences were found on the discomfort scores between the bag and the baskets for all body parts.
During the coffee cheery picking task, however, the large basket caused a significantly higher load than the bag on the right shoulder muscle that is responsible for rotating and lifting the upper arm sideways. Workers also reported that the large basket was considered poor. The increased shoulder muscle load might be related to the large diameter of the basket that forced the workers to lift their upper arms sideways during coffee cherry picking.


This chart shows Large basket caused higher shoulder muscle load MVC during coffee cherry picking compared to small baskets and bags.  MVC  percent of maximal muscular effort
Large basket caused higher shoulder muscle load during coffee cherry picking
(%MVC percent of maximal muscular effort)

This illustrates Properly adjusting the shoulder belt length is important to prevent interference with arm movements.
Properly adjusting the shoulder
belt length is important to prevent
interference with arm movements.

In the task of walking with full bag/baskets, the bag and the large basket required significantly higher shoulder muscle loads compared to the small basket. Workers also commented that the bag was uncomfortable during walking. This could be partially explained by the fact that the diameter of the bag might still be too big, forcing the workers to lift their arms during walking. This finding gave us direction in modifying the bag to make it smaller. This also suggests that it is critical that the shoulder belt of the bag be properly adjusted so the bag does not interfere with arm movements.

During the task of dumping a full basket or bag, use of the bag significantly lowered the low back muscle load compared to both baskets. This fulfilled the original design objective to reduce the physical load on the low back. However, the bag seemed also caused higher shoulder muscle load on the left body side compared to the small basket. This may suggest that we may have to carefully consider the design of the release mechanism on the side of the bag to make it easier to release a full bag.


This illustrates the bag significantly lowered the load on the low back during dumping coffee cherry task picture 1 (round basket), the bag significantly lowered the load on the low back during dumping coffee cherry task in picture 2 bag, and the bag significantly lowered the load on the low back during dumping coffee cherry task in picture 3 (rectangular basket)
The bag significantly lowered the load on the low back
during dumping coffee cherry task

Comparing muscle loadings between the different coffee harvesting tasks, it was obvious that the task of lifting and carrying the 120 lbs large sack was the most physically demanding task. The muscle loading on the low back and shoulders were significantly higher during this task than any of the other coffee harvesting tasks. Although the present study did not focus on improvements to this task, we had discussions on possible solutions with farm owners and harvest workers. We would hope that in the near future they may identify and implement feasible solutions to help improve the work conditions for the coffee harvesting workers.


This illustrates The task of lifting and carrying the large sack at the end of day caused high risk to the workers, picture 1 on the back, picture 2 on back (side view), and picture 3 lifting
The task of lifting and carrying the large sack at the end of day caused high risk to the workers.

Who collaborated with us on this project?

Several researchers, Rogelio José Caballero Martínez, Cipriano Mercedes Sandoval Sánchez, and Marcos Aurelio Vanegas Peña from CISTA - Universidad Nacional Autónoma de Nicaragua-Leon assisted in the field data collection. We hope that this experience will help them in the future to conduct ergonomics research and applications in Nicaragua. This project also received encouragement, support and financial contributions from the International Ergonomics Association (IEA), Japan Ergonomics Association, 4C Association, Pueblos en Accion Comunitaria (PAC) in Nicaragua, Washington State Department of Labor and Industries, and Universite Nacional-Autonomous, Leon.

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