Cotton salivette sampling devices

Salivary cortisol and chromogranin A were obtained from saliva samples. The athletes were requested to refrain from ingesting stimulating (e.g., coffee and chocolate) or dye containing substances, and from brushing their teeth during the three hours before assessment. Saliva samples were collected by chewing regular cotton salivette sampling devices (Sarstedt, Nümbrecht, Germany), thus without chemical stimulants. Samples were kept on ice and then stored at -20°C until the day of analysis. At the day of the analysis, saliva samples were centrifuged 10 min at 2000 x g to remove particulate material. Hormonal determinations were obtained by using the Human Chromogranin A ELISA Kit (MyBiosource, San Diego, CA, USA) and Human Cortisol ELISA Kit (Diagnostics Biochem Canada Inc, London, Ontario, Canada) according to the manufacturers’ directions and were expressed as ng/ml. All samples were processed in duplicate during the same assay section.

To investigate the effects of tVNS on autonomic reactivity, subjects' heart rate and blood pressure (diastolic and systolic) were measured using the Intelli Wrap Manschette M500 device (Omron Healthcare, Medizintechnik Handelsgesellschaft mbH, Mannheim, Germany). In addition, their sAA levels were measured as a potential marker of endogenous noradrenergic activity (Warren et al., 2017 (link)). This was done by collecting saliva samples using cotton Salivette sampling devices (Sarstedt, Nümbrecht, Germany). Participants were asked to chew the swab from the Salivette for 60 s to activate salivation. The samples were stored frozen and later sent to the Dresden LabService GmbH for sAA analysis (Thoma et al., 2012 (link)).