This study was designed to investigate the influence of posture on salivary
cortisol concentrations in healthy volunteers. In a balanced cross-over de
sign 24 subjects were exposed at 1 week intervals to different body positio
ns (sitting [S], lying [L] upright [U]) for 20 min in each condition. Befor
e, during and after the experimental treatment measures of blood pressure,
heart rate and saliva samples for determining the free fraction of cortisol
were obtained. Furthermore, at corresponding time points a questionnaire o
n emotional stares was completed. In addition, subjects were requested to c
omplete personality questionnaires before the experiment and to rate their
emotional states during saliva sampling. Results clearly indicate that the
circadian decrease of cortisol concentrations was present only in the condi
tions [S] and [L] whereas in [U] salivary cortisol concentrations increased
significantly. As expected, heart rate accelerations associated with a mar
ked reduction of systolic blood pressure were observed in [U]. To further e
xamine the relationship between hormonal and cardiovascular responses as in
dicators of autonomic activation, correlations between change scores were c
omputed indicating that a relationship between cardiovascular responses and
cortisol increases is not restricted to [U]. Positive correlations were ob
served between changes in systolic blood pressure and changes in cortisol c
oncentrations in both conditions [U] and [L]. Posture does not affect emoti
onal stales indicating independence between posture induced physiological r
esponses and experienced discomfort. Posture therefore should be adequately
controlled, since those non-specific increases of hormones may interfere w
ith state or trait dependent responses. Data are discussed with respect to
the importance to control for posture in field and experimental studies and
to possible mechanisms of posture induced changes in cortisol. (C) 1999 El
sevier Science Ltd. All rights reserved.