Circulatory Strain, Estimated Energy Output and Catecholamine Excretion in Norwegian Coastal Fishermen

Abstract

Circulatory strain and energy output were determined in 24 Norwegian coastal fishermen during a total of 35 work-days by indirect assessment based on computerized analysis of the continuously recorded heart rate by portable tape recorders. Urinary excretion of catecholamines was assayed as an index of stress response. The average, estimated energy expenditure of all activities on board during the whole day amounted to the equivalent of 0·9–1·11/min oxygen uptake and corresponded to 34–39% of the fishermen's maximal aerobic power with occasional peaks up to 80%. The heart rate exceeded 50% of the fishermen's heart rate reserve for 9–23% of the observation periods. The most strenuous activities were pulling in the seine with a power block (oxygen uptake up to 2·7 1/min) and unloading the catch, taxing the subjects by more than 50% of their maximal aerobic power for two-thirds of the duration of these activities. Continuous monitoring of the heart rate revealed the intermittent character of practically all activities on board. In a parallel study the circulatory strain, energy output and catecholamine excretion were investigated in eight catch handlers on land during a total of 12 work-days. Handling the catch entailed a mean oxygen uptake of 0·9 1/min, corresponding to about 34% of the maximal aerobic power of the workers, with peak values considerably lower and of shorter duration than in the fishermen. The average (median) urinary excretion of norepinephrine (NE) and epinephrine (E) during the work-day was high in both investigated groups, 72 ng/min NE and 24 ng/min E in the fishermen, and 59 ng/min NE and 15 ng/min E in the catch handlers. The epinephrine excretion in the fishermen was significantly higher (p≤0·01) than in the catch handlers.