Age-related differences in muscle microvascular response and muscle oxygen uptake: a near infrared spectroscopy apporach

Abstract

Background: Blood flow to the limbs has shown to be significantly reduced in elderly when compared to their younger counterparts. The knowledge on the effect of age on microvascular function is still limited. Near infrared spectroscopy (NIRS) is a non-invasive method which can measure skeletal muscle microvascular responsiveness and muscle oxygen uptake. Although NIRS is thought to be a reliable method there are certain confounders like adipose tissue thickness over the muscle and physical fitness that should be considered. Objective: The main aim of this study was to further investigate if there is a difference in muscle microvascular response and muscle oxygen uptake (mVO2) between elderly and young, taking into consideration physical performance parameters and adipose tissue thickness (ATT). The secondary aim of this study is to investigate the difference between an arterial occlusion fixed for time and an arterial occlusion fixed for the level of desaturation, between elderly and young. Methodology: A total of 37 participants completed the testing protocols, 19 young (25±0,5 years) and 18 elderly (69±1,4 years). To measure the participants microvascular response and mVO2 two arterial occlusion tests (AOT) were performed, one with a fixed duration (AOT10) and one with a fixed desaturation (AOT20). The performance parameters measured were peak-incremental dynamic handgrip test (IHT-peak) and whole body peak oxygen uptake (VO2-peak). Results: No difference in microvascular response and mVO2 between elderly and young, in the m. vastus lateralis (VL). In the m. flexor digitorum superficialis (FDS) there was observed a higher mVO2 for the young group. We found a relationship between ATT for both microvascular response and mVO2 in the VL. While in the FDS there was only observed a relationship between ATT and microvascular reperfusion rate (RR). We did also find a weak relationship between peak IHT-peak duration and the microvascular hyperaemic response (ΔSmO2-max) in the FDS. Our study showed no difference in microvascular response and mVO2 between elderly and young when using AOT20. While we did observe a difference in microvascular response and muscle oxygen uptake between AOT20 and AOT10. Conclusion: We found no difference in microvascular response and mVO2 between elderly and young for neither AOT10 nor AOT20. We did observe that ATT did affect the NIRS-signals. We found a relationship between IHT-peak duration and microvascular hyperaemic response. We did observe a larger microvascular response for the AOT10 compared to AOT20.

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