Abstract

Objectives This study aimed to compare exercise-induced changes in serum and salivary concentrations of cardiac troponin-I (cTnI) in athletes during and after a marathon.

Methods Thirty-six male runners were recruited. Eighteen participants in group 1 completed a marathon (42.195 km), while eighteen participants in group 2 did not undergo this exercise. Blood and saliva samples were collected at twelve different time points and then analyzed for cTnI using an immunoassay.

Results Biphasic cTnI release into the circulation was observed during and after the marathon. Moreover, a similar pattern of biphasic cTnI elevation was found in saliva. In group 1, salivary and serum concentrations of cTnI first peaked after 60 min of exercise (0.67±0.08 ng/mL and 0.76±0.07 ng/mL), decreased slightly towards the end of the marathon (0.40±0.06 ng/mL and 0.46±0.06 ng/mL), and then reached a second, higher peak 4 h post-exercise (0.72±0.09 ng/mL and 0.82±0.09 ng/mL), returning to baseline by 48 h after marathon completion (0.16±0.04 ng/mL and 0.18±0.04 ng/mL). In group 2, there were no time-dependent changes in cTnI concentrations in both saliva and serum. Deming regression and Passing–Bablok regression demonstrated that there was proportional agreement between salivary and serum levels of cTnI in both groups at all twelve time points. The Bland–Altman method revealed that there was a negative differential bias but no proportional bias in the data.

Conclusions Documenting a similar, biphasic pattern of cTnI elevations in saliva and serum during and after the marathon provides a reliable non-invasive alternative without requiring a blood draw.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This study was funded by RSF [grant number 25-75-00109].

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study was approved by the Local Ethics Committee of Lobachevsky University (Nr. 2, 22.09.2025) and was conducted in accordance with the principles set forth in the Declaration of Helsinki.

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Yes

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Yes

Data Availability

The data that support the findings of this study are available on request from the corresponding author.

AbbreviationsAMIAcute myocardial infarctionCIConfidence intervalcTnCardiac troponincTnICardiac troponin-IcTnTCardiac troponin-TOLSOrdinary least squaresPOCPoint-of-careSDStandard deviation