Effect of working position and cold environment on muscle activation level and fatigue in the upper limb during manual work tasks

Julie Renberg,Øystein Nordrum Wiggen,Per Øyvind Stranna Tvetene,Hilde Færevik,Mireille Van Beekvelt,Karin Roeleveld

doi:10.1016/j.ergon.2020.103035

Abstract

Several occupational groups are exposed to periods of low ambient temperatures while performing manual work tasks outdoors. Work tasks typically include heavy lifting, tool handling, and overhead work. This study evaluated the effect of working position and cold environment on muscle activation level (%RMSmax) and fatigue in the upper limb during manual work tasks. Fourteen male participants (25 ± 3 years, 80.9 ± 6.4 kg, 182 ± 5 cm) completed a 2-h test protocol consisting of five test periods alternating with four work periods, wearing identical sets of clothing, under cold (−15 °C) and control (5 °C) conditions. The work periods consisted of manual work at the hip level, manual overhead work, and a lifting exercise. The test periods consisted of isometric maximal voluntary contractions (MVC) and seated rest. Skin temperatures decreased during cold exposure, especially in the extremities. %RMSmax in the forearm was higher in the cold condition both during overhead work and work at the hip level than that for the same work in the control condition, especially at the end of the test when the difference was approximately 25% (equating to 2–3 %RMSmax). For the middle deltoid muscle, the %RMSmax was approximately three times (or 10 %RMSmax) higher during overhead work than work at the hip level, but there was no additional cost of working in the cold. Signs of deltoid muscle fatigue (decrease in electromyography median power frequency and an increase in %RMSmax) were observed during the overhead work periods in both temperature conditions. No decrease in MVC, as a sign of overall muscle fatigue, was observed in either condition. Relevance to industryThis study demonstrated that when wearing suitable cold-weather protective clothing, the adverse effect of work posture is much higher than that of cold on muscle demand and physical strain.

Highlights

Several occupational groups, such as industrial workers, miners, and petroleum workers, are exposed to periods of low ambient temperatures and harsh climatic conditions while performing manual work tasks outdoors
The muscle activation level for the deltoid muscle during work high (WH) was approximately 15 %RMSmax and increased slightly over the working periods in both the cold and control conditions (F (1.3, 17.5) = 5.44, p = 0.024); there were no significant differences between the two ambient temperature conditions (F (1, 13) = 0.64, p = 0.439) or any interaction effect (F (3, 39) = 1.00, p = 0.402) (Fig. 2)
The two ambient temperature conditions in our experiments had no effect on wrist flexion maximal voluntary contractions (MVC), shoulder abduction MVC, and concurrent RMSmax of the middle deltoid muscle (DE) and flexor digitorum super ficialis (FDS); these variables did not change over time (Table 1)

Summary

Introduction

Several occupational groups, such as industrial workers, miners, and petroleum workers, are exposed to periods of low ambient temperatures and harsh climatic conditions while performing manual work tasks outdoors. Work tasks typically include heavy lifting, tool handling, and overhead work. The occupational risk factors for developing musculo skeletal disorders include heavy physical work (da Costa and Vieira, 2010), manual material handling, and working with hands raised above the head level (Mayer et al, 2012). Exposure to moderately cold conditions has been found to increase muscle activation, thereby reducing the neuromuscular efficiency, in several upper extremity muscles during repetitive work in ambient temperatures of 4 ◦C–10 ◦C (Oksa et al, 2002, 2006, 2012; Piedrahita et al, 2008; Sormunen et al, 2009).

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