[The active butanol detection threshold remains the same during exercise].

Background: The active butanol detection thresholds (B-DT), determined using the sniffin' sticks, show a high intra- and inter-individual test-retest reliability, although the internal stimulus concentration may vary considerably depending on the dilution of the external stimulus concentration with odorless ambient air during active sniffing. There are various hypotheses for this surprising result. In this study, it should be tested whether a larger respiratory effort (vigor) under physical stress changes the active B-DT.

Methods: In 28 young, healthy, normosmic adults, sitting on a stationary bicycle ergometer at rest phase, during aerobic exercise and in the recovery phase, the monorhinal B-DT using Sniffin' Sticks were determined. Various vital parameters such as blood pressure, heart frequency, body temperature, respiratory frequency and blood lactate characterized the three test phases. The individual stress perception was estimated according to the Borg scale.

Results: The B-DT did not change in the three test phases. All examined vital parameters were significantly larger in the loading phase than in the resting phase. In the case of a moderate to severe stress sensation (Borg-scale: 13-15), an aerobic physical stress could be confirmed on the basis of the vital parameters.

Conclusions: The investigations support the hypothesis that vigor is not the decisive factor for a constant olfactory perception of external equal stimulus concentrations. The integration of internal stimulus concentration and nasal flow velocity and the empirical evaluation of the current odor concentration probably play a greater role.