Manual Tasks -- Pulling Rope

HS had signed on as a processor on a factory fishing trawler. The vessel was shorthanded and HS was given the opportunity to perform various tasks as a deckhand. If he did well, it could mean a promotion.

Towards the end of HS's 16-hour shift as a fish processor, he was asked to help out on deck. The net was being cleaned and mended. The deckhand in charge, IR, asked HS to pull the sling rope from underneath the net. HS had witnessed this task being performed several times, but had only performed it once before.

Aboard this vessel, there were three ways that the rope was removed from underneath a layer of netting and in the following sequence:



1) Manually, where a single deckhand pulled on one end of the rope until the rope was pulled clear of the net;

2) Manually, where two deckhands pulled on one end of the rope until the rope was pulled free; and

3) Mechanically, where the rope was pulled out using a hoist.

According to HS, he grabbed hold of the rope, bent his back leg and pushed his front foot against the net as he pulled backwards with both arms. He stated that he experienced a sharp pain in his back, which quickly disappeared. HS was not able to remove the rope. IR came over to assist him in performing the task. They both pulled, and HS once again experienced a sharp pain in his lower back. Again, the rope did not budge. IR then made the decision to make use of mechanical means to remove the rope. HS sustained injuries to his lower back that he attributed to the described task.

HF Issues: Can pulling on a rope in the manner described by HS place significant stress on the lumbar spine? If so, what could have been done to reduce the likelihood of injury?

HF Investigation: Information was obtained on HS's height and weight and the range of postures that he likely assumed in performing the task. Additional information included, but was not limited to: the weather at the time of the incident; the clothing and footwear worn by HS; and variability in the amount of drag required to slide the rope across a section of netting.

HF Analysis: A 3D computer model of HS was created to assist in establishing the range of postures he likely adopted in pulling on the rope. The figures were then exported to a computer application, MannequinPRO, for further analysis. A literature search revealed the maximal exertion level for a pull posture that was very similar to the one adopted by HS.

A review of the research literature indicated that under conditions of unsure footing, the compressive load on the lower back may be significantly greater than the estimate arrived at by traditional methods, such as the one I employed.

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