Repeatability of Respiratory Exchange Ratio Time Series Analysis

Area of Science:

• Exercise Physiology
• Metabolic Research
• Biostatistics

Background:

• Reliability of physiological measures is crucial for accurate exercise science research.
• Time series analysis of respiratory exchange ratio (RER) is increasingly used, but its repeatability needs further investigation.
• Few studies have assessed the repeatability of RER time series analysis under consistent conditions.

Purpose of the Study:

• To evaluate the repeatability of respiratory exchange ratio (RER) measurements using time series analysis.
• To compare RER repeatability at two sub-maximal exercise intensities: 30% and 60% of ventilatory threshold (VT).

Main Methods:

• A repeated-measures design involving two trials separated by 7 days.
• Participants (n=12) completed a peak oxygen uptake test followed by two 15-minute cycle ergometer tests at 30% and 60% VT.
• Statistical analyses included paired t-tests, coefficient of variance, intraclass correlation coefficients (ICC), and Bland-Altman plots to assess RER repeatability.

Main Results:

• No significant differences were found between trials for mean RER or sample entropy (SampEn) of RER at either intensity.
• High repeatability was observed for mean RER (ICC=1.00 at 30% VT, ICC=0.92 at 60% VT).
• Repeatability for SampEn of RER varied, with lower ICC values at 60% VT (ICC=0.81 at 30% VT, ICC=0.25 at 60% VT).

Conclusions:

• Respiratory exchange ratio (RER) measurements are repeatable during steady-state cycle ergometry at 30% and 60% of VT.
• Mean RER demonstrates high reliability, while the complexity of RER (SampEn) shows potential variability at higher sub-maximal intensities.
• Further research with larger sample sizes and varied exercise intensities is recommended to confirm these findings.