The aim of this study was to examine the effects of assuming constant reduced scattering coefficient (μ\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({^\prime}_{\mathrm{s}}\) \end{document}) on the muscle oxygenation response to incremental exercise and its recovery kinetics. Fifteen subjects (age: 24 ± 5 yr) underwent incremental cycling exercise. Frequency domain near-infrared spectroscopy (NIRS) was used to estimate deoxyhemoglobin concentration {[deoxy(Hb+Mb)]} (where Mb is myoglobin), oxyhemoglobin concentration {[oxy(Hb+Mb)]}, total Hb concentration (Total[Hb+Mb]), and tissue O₂ saturation (Sti\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{\mathrm{O}_{2}}\) \end{document}), incorporating both continuous measurements of μ\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({^\prime}_{\mathrm{s}}\) \end{document} and assuming constant μ\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({^\prime}_{\mathrm{s}}\) \end{document}. When measuring μ\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({^\prime}_{\mathrm{s}}\) \end{document}, we observed significant changes in NIRS variables at peak work rate Δ[deoxy(Hb+Mb)] (15.0 ± 7.8 μM), Δ[oxy(Hb+Mb)] (−4.8 ± 5.8 μM), ΔTotal[Hb+Mb] (10.9 ± 8.4 μM), and ΔSti\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{\mathrm{O}_{2}}\) \end{document}(−11.8 ± 4.1%). Assuming constant μ\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({^\prime}_{\mathrm{s}}\) \end{document} resulted in greater (P < 0.01 vs. measured μ\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({^\prime}_{\mathrm{s}}\) \end{document}) changes in the NIRS variables at peak work rate, where Δ[deoxy(Hb+Mb)] = 24.5 ± 15.6 μM, Δ[oxy(Hb+Mb)] = −9.7 ± 8.2 μM, ΔTotal[Hb+Mb] = 14.8 ± 8.7 μM, and ΔSti\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{\mathrm{O}_{2}}\) \end{document}= −18.7 ± 8.4%. Regarding the recovery kinetics, the large 95% confidence intervals (CI) for the difference between those determine measuring μ\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({^\prime}_{\mathrm{s}}\) \end{document} and assuming constant μ\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({^\prime}_{\mathrm{s}}\) \end{document} suggested poor agreement between methods. For the mean response time (MRT), which describes the overall kinetics, the 95% confidence intervals were MRT − [deoxy(Hb+Mb …