Innovaties in de glasgroenteteelt: vergelijking van verschillende methoden voor het laten zakken van tomatenplanten

Innovations in horticulture: comparison of different working methods for lowering of tomato plants

Huub H.E. Oude Vrielink et al.

 

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Summary

In The Netherlands, the modern way of tomato production involves a high wire system. Here, metal hooks hold a rope that guides the growing tomato plant. Because the plants keep growing during the season, each rope is to be lowered periodically, which requires one-handed lifting. Because each plant weighs 4-6 kg and a complete cycle costs only 1-2 seconds, the task is considered to be strenuous and highly repetitive.

Some alternative systems are available or under development, but their eventual load relieving effect is unknown. The present study considered some alternative systems from a theoretical viewpoint and investigated the effects of one particular alternative hook, the Tomguide. This hook eliminates most of the lifting part of the task because of application of a reel on which the rope is winded.

The research involved seven experienced persons in six companies. All of the persons performed both tasks, i.e. the standard hook and the Tomguide. Muscular loading, experienced effort and working speed were measured during and after each task. Muscular loading was measured in four shoulder (trapezius and deltoid, left and right side) and two upper arm (biceps, left and right) muscles, applying electromyography (EMG). Static, median and peak load, relative to maximal activation, were calculated. Experienced effort was scored using a 10-point rating scale and a body diagram showing 14 body regions.

EMG results showed a significant decrease in peak activity for both upper arm muscles when using the Tomguide. Median activity was reduced only for the right upper arm. If all 6 muscles were pooled, peak activity was reduced significantly, while median activity showed a tendency, without reaching significance. No difference was measured for any of the individual shoulder muscles measured. Experienced effort decreased significantly for the shoulder and upper arm regions, both left and right, in case of the Tomguide. It was observed that the Tomguide task lead to an increase in working time by 27%, compared to the standard hook, possibly partly due to insufficiently functioning of the mechanical brake on the reel.

Figure: the workload for most of the body regions (X-as) is judged lower for the Tomguide (light gray) as compared to the standard metal hook (dark gray)

It is concluded that the Tomguide, and probably also comparable reel rope systems, contribute to a reduction of muscular load, in particular of the upper arm muscles, because lifting of the plants is strongly reduced. Because most workers copy their working height for the standard hook into the new situation, attention must be paid to instruction of the proper working height, in order to prevent unnecessarily high load of the shoulder muscles. Besides, final conclusions of the labour demand can only be drawn if the reel system applied is functioning well. The braking system of the Tomguide tested here did not allow for a relaxed working technique.

    

Source: www.ergolabresearch.eu.