Date of Award

12-2025

Degree Type

Honors College Thesis

Academic Program

Kinesiology BS

Department

Human Performance and Recreation; Kinesiology

First Advisor

Jonathon Stavres, Ph.D.

Second Advisor

Stephanie Smith, Ph.D.

Advisor Department

Human Performance and Recreation; Kinesiology

Abstract

Cardiorespiratory fitness, measured as maximal oxygen consumption (VO₂max) is a critical predictor of all-cause mortality and overall cardiovascular health. Metabolic carts are the current gold standard for evaluation of VO₂max, but are inaccessible to most facilities and individuals, and are expensive ($20,000+). Near-Infrared spectroscopy (NIRS) has emerged as an accessible and affordable ($5,000-$10,000) alternative for evaluating skeletal muscle oxygenation kinetics and mitochondrial oxidative capacity. However, there is limited research in examining whether NIRS-derived oxygen desaturation rates can be a predictor of cardiorespiratory fitness markers (such as VO₂max and peak power output [PPO]), and whether these measurements show a superior predictive validity when collected during resting conditions, or during post-exercise conditions. Therefore, the purpose of this study is to investigate the relationship between NIRS oxygen desaturation rates and cardiorespiratory fitness markers (VO₂max/PPO) during resting and post-exercise circulatory occlusion in adults. The study consisted of 33 participants (12 males, 21 females, ages 19-50) with a wide range of cardiorespiratory fitness levels (18.4 - 47.2 mL/kg/min). Participants completed a maximal exercise test on a cycle ergometer followed by NIRS assessments coupled with total arterial occlusions during both resting and post-exercise conditions. Analysis consisted of linear regression models that examined the relationship between NIRS-derived desaturation rates (tissue saturation index [TSI], oxygenated hemoglobin [O₂Hb], deoxygenated hemoglobin [DO₂Hb]) and fitness markers (VO₂max/PPO). Results demonstrated a significant association between all three NIRS parameters and VO₂max (p < 0.01), with DO₂Hb explaining the highest variance (R² = 0.377, p < 0.001). Peak power output (PPO) displayed a significant association with DO₂Hb and O₂Hb but displayed no association with TSI. O₂Hb had the strongest association with PPO during resting conditions (p < 0.001) and PECO (p = 0.04). Importantly, NIRS measurements obtained during post-exercise circulatory occlusion (PECO) consistently demonstrated stronger associations with both VO₂max and PPO compared to resting conditions. These findings suggest that NIRS-derived oxygen desaturation rates found during post-exercise circulatory occlusion (PECO) may serve as valid predictors of cardiorespiratory fitness markers, which could provide a more accessible and affordable alternative to traditional, exhaustive metabolic testing. Future research can further this topic with larger sample sizes and could explore developments in standardized protocols that could be used in both clinical and athletic settings.

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