Reliability of Exhaled Acetone and Isoprene in Healthy Active Adult Responses to Sub-maximal Treadmill Exercise: A Pilot Study

Abstract

This study investigates the test–retest reliability of exhaled acetone and isoprene as potential biomarkers for monitoring exercise-induced physiological changes. Ten healthy active males (age 22.7 ± 3.7 years, height 182.4 ± 6.8 cm, body mass 80.12 ± 8.5 kg, body mass index 24.0 ± 1.4 kg/m², VO_2peak 55 ± 4 mL/kg/min, physical activity 322 min/week) provided baseline measures before undergoing a VO_2peak test and two treadmill exercise trials, interspersed by 7-days’ rest. Treadmill exercise consisted of 20 min at 80% of VO_2peak speed. Breath samples were collected before exercise, 10 min, and 24 h after exercise, using glass containers and solid-phase microextraction fibres, and analysed by gas-chromatography mass-spectrometry. Exhaled acetone exhibited poor internal consistency (Cronbach’s α = − 0.184) and agreement (ICC = − 0.096 [− 0.836–0.607], P = 0.592) with a high technical error (TE = 2.38 × 10⁶) and coefficient of variation (CV = 90%). In contrast, exhaled isoprene provided satisfactory internal consistency (Cronbach’s α 0.817) and good agreement (ICC = 0.699, P = 0.009), with a lower technical error (TE = 1.24 × 10⁶) and coefficient of variation (CV = 28%). Quadratic regression showed a decrease in isoprene 10 min after exercise during trial 1 (P < 0.01) and trial 2 (P < 0.05) and returned to baseline levels after 24 h. While acetone’s reliability was questionable, isoprene levels following 20 min of submaximal treadmill exercise are notably reproducible among healthy active males.

Keywords

Breath analysis / Cardiorespiratory fitness / Coefficient of variation / Exercise testing / Reproducibility / Volatile organic compounds

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Funding

Federation University Australia

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