2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
CARDIOVASCULAR SYMPTOMS LIMIT THE HEAT STRESS
EXERCISE OF ROOF AND ASPHALT WORKERS?
Henna Hämäläinen, Raija Ilmarinen, Harri Lindholm, Heli Sistonen, Kaarina Eklöf
Health and Work Ability, Finnish Institute of Occupational Health (FIOH), Helsinki, Finland
Contact person: henna.hamalainen@ttl.fi
INTRODUCTION
Good physical fitness improves the capacity of an employee to adapt to a hot and humid
working environment. Excellent maximal oxygen consumption (VO2max), however, does not
protect against the detrimental effects of high heat stress. In addition to physical fitness, heat
tolerance depends on age, sex, cardiorespiratory fitness, training history, overweight, health,
and medication. Genetic factors also affect individual thermal regulation. Circulatory
insufficiency usually precedes excessive elevation of body temperatures in the limitation of
physical performance of a normal worker in a hot and humid environment. Rapid changes in
systolic blood pressure often constitute the first sign of failing circulation. In such cases also
the risk of work-related accidents is elevated.
The aim of this study was to investigate the responses of heat stress test (HST) on roof and
asphalt workers. The main interest was especially the responses of heart and cardiovascular
function during the test. Also the possible usefulness of heart rate variability (HRV) in
recognizing and anticipating hemodynamic failure during HST was on focus.
METHODS
The study group consisted of 13 healthy and voluntary professional male roof and asphalt
workers with an average age of 35 (25-49) y, height of 177 (171-190) cm, weight of 85 (58-
129) kg, body area of 2.0 (1.7-2.5) m 2 , body mass index (BMI) of 27 (20-36) kg/m 2 , and
evaluated VO2max of 37 (22-49) ml/kg/min. The subjects gave written consent before the
experiment and received no payment for their participation in the study. Before the HST, a
medical examination was performed and the aerobic fitness of the participants was evaluated
by submaximal bicycle ergometer (Ergoline, Bitz, Germany) test. VO2max was calculated
indirectly from the heart rate response by utilizing the FitWare software (Fitware Pro 3,
Tamro Med-Lab, Finland). The termination point of the submaximal bicycle ergometer test
was reached when the heart rate was 85% of the age-related (Jones 1988) maximum heart
rate. Individual correlation between heart rate and oxygen consumption was measured during
the test (Vmax29, SensorMedics Corporation, USA).
A HST, standardized by FIOH, was used to evaluate the physiological responses reflecting
heat strain. The test was performed in a climatic chamber under carefully controlled thermal
conditions (Ta 35°C, RH 65%, va