Cold, fitness and the exercise electrocardiogram. A 20 year longitudinal study of Canadian Inuit.

A 20 year longitudinal study has examined fitness, lung function and exercise electrocardiograms in the Inuit of Igloolik (NWT, 69 degrees 40' N). When first examined (1969/70), an energy expenditure of up to 16 MJ/day was estimated from Kofranyi-Michaelis respirometry. Step test predictions of maximal oxygen intake were also high initially, but values declined progressively with acculturation to a sedentary lifestyle. Throughout the 20 years, right-branch bundle block (RBBB) has been somewhat more prevalent than in southern Canada. The majority of those affected have shown no more than slight R-wave notching. In 1969/70, a few of the more marked cases of RBBB may have been attributable to chronic respiratory disease, but the majority of cases have shown high normal values for both lung function and maximal oxygen intake. We thus conclude that the major cause of RBBB in this community is a ventricular hypertrophy due to the vigorous physical demands of the traditional lifestyle.