Age-Related Changes in Skeletal Muscle Oxygen Utilization

Figures

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  Figure 1. Chromophores present in human tissue plotted against the absorption spectra (natural logarithm base). Water, fat, collagen, deoxygenated hemoglobin (Hhb), oxygenated hemoglobin (O2Hb), melanin, and cytochrome oxidase (Cytox) are observed in the 100 to 3000 nm region. The isosbestic point, the point at which the extinction coefficient of oxygenated and deoxygenated hemoglobin is equal, is plotted at 800 nm. Hhb and O2Hb are highlighted as being the primary sources of obtained NIRS signals around the isosbestic point. Y-axis absorption coefficient units: μa [cm−1]; X-axis wavelength units: λ [nm]. Reprinted with permission from ref. [45]. Copyright 2014 Elsevier.

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  Figure 2. Mean SmO2 from rest to maximal exercise in younger (open circle) and older (solid circle) individuals. Statistically significant differences in SmO2 were noted at rest and at each point up to VO2max over the course of standard ramp exercise test. ♦ p < 0.01 between older and younger groups. Reprinted with permission from ref. [13]. Copyright 1999 Taylor & Francis.

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  Figure 3. Oxygen delivery to muscle is tightly regulated by blood flow. With advancing age, decreased vasodilation, endothelial cell dysfunction, reduced nitric oxide production, and decreased capillary supply and function are each responsible for reduced blood flow observed with aging and are attributed to mismanagement of ROS. Furthermore, content and function of the cellular machinery tasked with utilizing oxygen, mitochondria, are also impaired with aging. These age-related impairments in the oxygen delivery cascade ultimately lead to reductions in SmO2 levels at rest, during exercise, and recovery from exercise.