Fitness Level and Not Aging per se, Determines the Oxygen Uptake Kinetics Response

Abstract

Although aging has been associated to slower trueV˙O2 kinetics, some evidence indicates that fitness status and not aging per se might modulate this response. The main goal of this study was to examine the trueV˙O2, deoxygenated hemoglobin+myoglobin (deoxy-[Hb+Mb]) kinetics, and the NIRS-derived vascular reperfusion responses in older compared to young men of different training levels (i.e., inactive, recreationally active, and endurance trained). Ten young inactive [YI; 26 ± 5 yrs.; peak trueV˙O2 (trueV˙O2peak), 2.96 ± 0.55 L·min−1], 10 young recreationally active (YR; 26 ± 6 yrs.; 3.92 ± 0.33 L·min−1), 10 young endurance trained (YT; 30 ± 4 yrs.; 4.42 ± 0.32 L·min−1), 7 older inactive (OI; 69 ± 4 yrs.; 2.50 ± 0.31 L·min−1), 10 older recreationally active (OR; 69 ± 5 yrs.; 2.71 ± 0.42 L·min−1), and 10 older endurance trained (OT; 66 ± 3 yrs.; 3.20 ± 0.35 L·min−1) men completed transitions of moderate intensity cycling exercise (MODS) to determine trueV˙O2 and deoxy-[Hb+Mb] kinetics, and the deoxy-[Hb+Mb]/trueV˙O2 ratio. The time constant of trueV˙O2 (τtrueV˙O2) was greater in YI (38.8 ± 10.4 s) and OI (44.1 ± 10.8 s) compared with YR (26.8 ± 7.5 s) and OR (26.6 ± 6.5 s), as well as compared to YT (14.8 ± 3.4 s), and OT (17.7 ± 2.7 s) (p < 0.05). τtrueV˙O2 was greater in YR and OR compared with YT and OT (p < 0.05). The deoxy-[Hb+Mb]/trueV˙O2 ratio was greater in YI (1.23 ± 0.05) and OI (1.29 ± 0.08) compared with YR (1.11 ± 0.03) and OR (1.13 ± 0.06), as well as compared to YT (1.01 ± 0.03), and OT (1.06 ± 0.03) (p < 0.05). Similarly, the deoxy-[Hb+Mb]/ trueV˙O2 ratio was greater in YR and OR compared with YT and OT (p < 0.05). There was a main effect of training (p = 0.033), whereby inactive (p = 0.018) and recreationally active men (p = 0.031) had significantly poorer vascular reperfusion than endurance trained men regardless of age. This study demonstrated not only that age-related slowing of trueV˙O2 kinetics can be eliminated in endurance trained individuals, but also that inactive lifestyle negatively impacts the trueV˙O2 kinetics response of young healthy individuals.

The association between near‐infrared spectroscopy assessment of microvascular reactivity and flow‐mediated dilation is disrupted in individuals at high risk for cardiovascular disease

“…Thus, properly assessing vascular function within conduit artery and the microvascular circulation is important for prevention, early detection, and monitoring of CVD . In relation to this, the use of near‐infrared spectroscopy (NIRS) combined with vascular occlusion test (VOT) technique (NIRS‐VOT) has been demonstrated to be a useful tool for assessment of microvascular function . This technique evaluates microvascular reactivity by assessing the steepness of the upslope of the muscle oxygen saturation signal (reperfusion slope, % per s), typically following a 5‐min period of limb occlusion .…”

“…the use of near-infrared spectroscopy (NIRS) combined with vascular occlusion test (VOT) technique (NIRS-VOT) has been demonstrated to be a useful tool for assessment of microvascular function. [4][5][6][7][8][9][10][11][12][13] This technique evaluates microvascular reactivity by assessing the steepness of the upslope of the muscle oxygen saturation signal (reperfusion slope, % per s), typically following a 5-min period of limb occlusion. 7,10,11 The NIRS-VOT approach has been shown to provide repeatable and reliable measures of vascular responsiveness within the lower and upper limb microvasculature, 14,15 and to offer a noninvasive and "low-cost" alternative to the most commonly used methods of microvascular function assessment (ie, blood flow response to vasoactive substances assessed by Doppler ultrasound).…”

Ability of The Cardiorespiratory System to Adapt to Exercise is Impaired in Individuals With Severe Post-Stroke Fatigue

“…In healthy adults, the acceleration of τV̇O2 has been reported to occur in the early period of endurance training, and V̇O2 at peak exercise can subsequently increase [20,21]. Additionally, a previous study reported that τV̇O2 was shorter in the recreationally active group than in the inactive group; however, there was no significant difference in V̇O2 at peak exercise between the two groups [19]. These results of previous studies indicated that τV̇O2 was more sensitive than V̇O2 at peak exercise in assessing cardiorespiratory functional changes, which may explain our results that a higher FSS score was significantly correlated with a longer τV̇O2 but not with V̇O2 at peak exercise.…”

“…The submaximal constant-load exercise test started with resting on the cycle ergometer for 3 min, followed by performing exercise at 80% of the workload corresponding to the ventilatory threshold for 6 min [19,34]. The protocol was repeated three times, with a rest between each repetition.…”

“…Tomczak et al [16] reported that τV̇O2 was greater in individuals with stroke than in age-, sex-, and activity-matched healthy adults. τV̇O2 has been reported to be more sensitive than V̇O2 at peak exercise in assessing cardiorespiratory functional changes associated with training and inactive lifestyle [19][20][21][22]. Therefore, we hypothesised that the severity of post-stroke fatigue could be associated more strongly with τV̇O2 than V̇O2 5 at peak exercise.…”