Muscular and metabolic load and manual function when working in the cold

Abstract

Work in cold environments bring challenges to maintain health and performance. Two important differences when working in cold compared to neutral or warm conditions are: personal protective clothing (PPC) worn and reduced tissue temperatures. The purpose of this thesis was to investigate the effect of low ambient temperatures, the use of cold-weather PPC and the combined effect of these on muscular and metabolic load and manual function during relevant work tasks.

Experimental laboratory studies were designed to simulate realistic scenarios, including the use of modern PPC and personal protective equipment (PPE) while performing relevant simulated tasks in temperature ranges frequently encountered during outdoor work in the cold. Paper I report a study of the effects of state-of-the-art cold-weather PPC and PPE on muscle activation level and metabolic rate during walking at moderate and high intensities. Paper II reports a study aimed at gaining new knowledge about how thermal responses, muscle activation levels and fatigue are affected by performing manual work task at a neutral and at an awkward working position in cold environments while wearing cold-weather PPC. Paper III reports a study that focused on how specific isometric manual task performance at different loads is affected by cold conditions leading to mild whole-body cold stress.

This thesis demonstrates that the muscular and metabolic loads increase in people wearing state-of-the-art cold-weather PPC and commonly used PPE when walking at both moderate and heavy work intensities. The results also show that a realistic extent of cooling increases the muscle activation level in the forearm during a simulated manual work task at different working positions in cold environments, but that similar responses was not measured for the shoulder muscle investigated. The results further show that mild whole-body cold stress combined with continuous low-intensity shivering does not affect the ability to maintain a steady force output with the hand and fingers during isometric contractions at low and moderate loads.

The practical application from these results is that to keep performance and comfort during cold work, PPC and PPE should be carefully selected to minimize the extra muscular and metabolic load of work. The cold-weather PPC should also be chosen to effectively limit heat loss to the environment to maintain optimal manual function while avoiding an increase in the muscular load in response to body cooling.