Ergonomics and Agriculture…It isn't as easy as picking daisies

The science of ergonomics tends to be most prevalent in the automotive arena even though there are similar work demands and characteristics occurring in other industries across the world.  Ergonomic and fundamental vehicle manufacturing processes have become two peas in a pod; yet, this same relationship is scarce when evaluating other industries such as agriculture.  Even though the application of ergonomics may not be as prominent in the agriculture field as the automotive, improvements are still transpiring to reduce the risk of injury for the worker and improve job conditions.   

A study conducted by Earle-Richardson, Jenkins, Strogatz, Bells and May (2006) assessed objective fatigue measures in apple harvest workers.  The purpose of the study was to develop simple back, shoulder or arm strength measures, which detect statistically significant drops in strength over one work day.  The experiment focused on 12 different muscle strength measures; eight were maximum contraction measures and four were timed endurance measures. 

The data suggests that in an agriculture setting such as apple harvesting, endurance measures may be a more effective method of quantifying fatigue versus maximum contraction measures.  Therefore, by knowing the appropriate fatigue quantification tools, ergonomists can direct their efforts towards correct solutions to reduce fatigue and risk of injury.  It is important to use the correct analysis tools when evaluating risk, regardless of the industry.

Furthermore, in a different study completed by Earle-Richardson, Jenkins, Strogatz, Bell, Freivalds, Sorensen and May (2008), electromyography (EMG) was used to asses an apple bucket design to reduce back strain.  The proposed new design of the apple bucket possesses the addition of a hip belt to reduce muscle fatigue as in seen in Figure 1. 

Even though workers welcomed the idea of the new designed bucket and it did not hinder their productivity in any way, the data did not show any reductions in muscle fatigue when assessed by tests of voluntary muscle strength.  Therefore, this is the reason why EMG amplitude measurements were taken on 15 different muscles of the subjects while wearing the intervention belt and without the intervention belt in multiple postures. 

The data for the intervention group showed substantial reductions in muscle recruitment of the middle and lower back muscles when bending forward.  It was identified that the magnitude of these muscle recruitment reductions correlates with the increase of flexion angle.  There were no meaningful reductions seen with the neck and shoulder muscles, but it was still concluded that wearing the intervention belt reduces muscle strain for apple pickers and possible other fruit pickers.  Interventions like this can be useful in a variety of different applications as it spreads the load across the body instead of one local area. 

Moreover, Meyer and Radwin (2007) performed a study comparing physical and psychophysical differences between stoop and prone postures in an agricultural harvesting task. Tasks would include anything that involves the picking of something from the ground, like picking daisies.  Prone postures were achieved by the subjects with use of a specialized workstation, as seen in Figure 2. 

The analyzed work duration for both postures was 30 minutes.  The variables used to evaluate the two postures included perceived discomfort, EMG, and heart rate (HR).  For all three measures differences were identified in favor of the prone posture.  Perceived discomfort was greater in the low back and extremities for stooped postures.  It was said that the discomfort was attributed to the prolonged static contraction of the lower back and hamstrings needed to support a stooped posture.  The results from the EMG showed that for the trapezius, the frequency and motions required for both postures contributed equally to localized muscle fatigue. 

The hand and arm motions for both postures produced similar results, although the prone participants worked for a longer duration.  The rest allowance between work sessions could provide enough recovery for the subjects that no muscle groups indicated a continued trend in the fatigue signal.  In terms of HR, there was a 35.2% increase above the resting HR for stooped postures compared to a 16.9% increase for prone postures.  The mean difference between resting and working was 25.7 bpm for stoop and 12.5 bpm for prone.  In general, during the stooped posture work, the HR was higher and more variable.  It was concluded that prone workstations have a significant advantage over stoop labor for short-term exposures and that further research is need regarding longer work durations.  These findings could really have an impact on farmers and engineers, in terms of designing work tools and processes.

Lastly, a cohort study conducted by Shipp, Cooper, Del Junco, Delclos, Burau, and Tortolero (2007) looked at severe back pain among farm workers who are high school students.  The purpose of the study was to evaluate potential risk factors for back pain among adolescents performing tasks that require bent/stooped postures and heavy lifting.  The method of conducting the study was a self-administered web-based survey, in which most of the items surrounded work exposure and severe back pain.  Results showed that the prevalence of severe back pain was 15.7% among farm workers and 12.4% among non-farm workers.  The prevalence increased to 19.1% among farm workers who also complete non farm work duties.  It was concluded that further investigation into this topic is needed.   

In conclusion, there is research being completed applying ergonomic principles and analysis methods to the agriculture field to better understand how people work.  With continued efforts down this path, the results would be a decrease in risk of injury along with an increase in quality and productivity.  This could have huge beneficial impacts to the farming industry as a whole, making it as sweet as apple pie.

References 

Earle-Richardson, G., Jenkins, P., Strogatz, D., Bells, E., & May, J. (2006).  Development and initial assessment of objective fatigue measures for apple harvest work.  Applied Ergonomics, 37, 719-727.

Earle-Richardson, G., Jenkins, P., Strogatz, D., Bell, E., Freivalds, A., Sorensen, J., & May, J.  (2008).  Electromyographic assessment of apple bucket intervention designed to reduce back strain.  Ergonomics, 51, 902-919.

Meyer, R., & Radwin, R. (2007).  Comparison of stoop versus prone postures for a simulated agricultural harvesting task.  Applied Ergonomics, 38, 549-555.

Shipp, E., Cooper, S., Del Junco, D., Delclos, G., Burau, K., & Tortolero, S. (2007).  Severe Back Pain Among Farmworker High School Students From Starr County, Texas: Baseline Results. Ann Epidemiol,17, 132-141.