Thermoregulatory Responses and Work Strain of Fishermen - A Field Study and a Laboratory Study
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- Institutt for biologi 
Fishermen on board deep-sea trawlers in the Barents and Norwegian Sea are exposed to low air temperatures, strong winds, high humidity, rain, snow and work with varying intensities. No studies have investigated the effect of environmental work factors on selected physiological parameters of fishermen on board Norwegian deep-sea trawlers. This study was therefore performed to increase knowledge about work strain and environmental challenges on factory and trawl deck, by recording heart rate (HR), core (Tc) and mean skin (Ts) temperatures of 25 fishermen during work on deep-sea trawlers. Short periods of hard (above 86% of HRmax) work, increased Tc by 0.8°C to 37.8°C and decreased Ts by 2.3°C to 29.8°C were measured on trawl deck, together with subjective reports of being warm and sweaty. On factory deck long periods of fairly light (between 52-66% HRmax) work, Tc of 37.4°C and Ts of 30.9°C were measured. Fishermen endures short periods of intermittent work with heavy work strain on trawl deck and long periods of repetitive work with light to moderate work strain on factory deck. The present study characterizes work strain and environmental challenges endured by fishermen, and can help identify risk exposures during work in cold and warm environments.Based on observations and measurements from the field study a laboratory study was conducted with the objective of studying the relationship between high (85%) and low (19%) relative humidity (RH) and sweat rate during inactive recovery after high intensity work in a warm environment (30°C). Ten male subjects volunteered to perform two 20-minute run-trials at 68 ± 4 % of maximal oxygen consumption followed by 36 minutes of upright inactive recovery. Regional sweat rate (RSR) was measured on the arm and back by technical absorbent pads at regular intervals and gross sweat loss was estimated from change in body weight. Tc, Ts, and HR were measured continuously during running and recovery. RSR were significantly (p<0.05) higher in high humidity, compared to low humidity conditions for both arm and back during running and inactive recovery. The highest sweat rates were observed on the back during the test in high humidity test with mean values of 1387 g m-2 h-1 during the last five minutes of running and 1379 g m-2 h-1 during the first five minutes of recovery. RSR showed weak to moderate correlations to local skin temperature during inactive recovery, but no correlations to local skin temperature during running. Tc continued to increase for three and seven minutes post-exercise in 19% RH and 85% RH respectively. HR was 11 bpm higher after running in 85% RH compared to 19% RH (p=0.001). Thermal load was higher during post-exercise recovery in high compared to low humidity conditions.