Influence of phase I duration on phase II VO2 kinetics parameter estimates in older and young adults.
ABSTRACT Older adults (O) may have a longer phase I pulmonary O(2) uptake kinetics (Vo(2)(p)) than young adults (Y); this may affect parameter estimates of phase II Vo(2)(p). Therefore, we sought to: 1) experimentally estimate the duration of phase I Vo(2)(p) (EE phase I) in O and Y subjects during moderate-intensity exercise transitions; 2) examine the effects of selected phase I durations (i.e., different start times for modeling phase II) on parameter estimates of the phase II Vo(2)(p) response; and 3) thereby determine whether slower phase II kinetics in O subjects represent a physiological difference or a by-product of fitting strategy. Vo(2)(p) was measured breath-by-breath in 19 O (68 ± 6 yr; mean ± SD) and 19 Y (24 ± 5 yr) using a volume turbine and mass spectrometer. Phase I Vo(2)(p) was longer in O (31 ± 4 s) than Y (20 ± 7 s) (P < 0.05). In O, phase II τVo(2)(p) was larger (P < 0.05) when fitting started at 15 s (49 ± 12 s) compared with fits starting at the individual EE phase I (43 ± 12 s), 25 s (42 ± 10 s), 35 s (42 ± 12 s), and 45 s (45 ± 15 s). In Y, τVo(2)(p) was not affected by the time at which phase II Vo(2)(p) fitting started (τVo(2)(p) = 31 ± 7 s, 29 ± 9 s, 30 ± 10 s, 32 ± 11 s, and 30 ± 8 s for fittings starting at 15 s, 25 s, 35 s, 45 s, and EE phase I, respectively). Fitting from EE phase I, 25 s, or 35 s resulted in the smallest CI τVo(2)(p) in both O and Y. Thus, fitting phase II Vo(2)(p) from (but not constrained to) 25 s or 35 s provides consistent estimates of Vo(2)(p) kinetics parameters in Y and O, despite the longer phase I Vo(2)(p) in O.
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ABSTRACT: [Purpose] The objective of this study was to determine the validity of pulmonary oxygen uptake kinetics in assessment of the ability of skeletal muscles to utilize oxygen. [Subjects] We evaluated 12 young, healthy males. [Methods] The subjects completed a series of tests to determine their peak oxygen uptake, pulmonary oxygen uptake kinetics at the onset of moderate-intensity treadmill exercise, and the rate of decline in electromyographic (EMG) mean power frequency (MPF) (EMG MPFrate) during one continuous, fatiguing, isometric muscle action of the plantar flexors until exhaustion at approximately 60% maximum voluntary contraction. We discussed the relationships between pulmonary oxygen uptake kinetics and EMG MPFrate reflecting the ability of skeletal muscles to utilize oxygen and between pulmonary oxygen uptake kinetics and peak oxygen uptake reflecting the ability to deliver oxygen to skeletal muscles. We hypothesized that pulmonary oxygen uptake kinetics may be more highly correlated with EMG MPFrate than peak oxygen uptake. [Results] Pulmonary oxygen uptake kinetics (33.9 ± 5.9 s) were more significantly correlated with peak oxygen uptake (50.6 ± 5.5 mL/kg/min) than EMG MPFrate (-14.7 ± 8.7%/s). [Conclusion] Pulmonary oxygen uptake kinetics is a noninvasive index that is mainly usable for evaluation of the ability of cardiovascular system to deliver oxygen to skeletal muscles in healthy young adults with slower pulmonary oxygen uptake kinetics (>20 s).Journal of Physical Therapy Science 11/2013; 25(11):1363-6. · 0.20 Impact Factor
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ABSTRACT: This study examined the impact of eccentric exercise-induced muscle damage on the rate of adjustment in muscle deoxygenation and pulmonary O2 uptake ([Formula: see text]) kinetics during moderate exercise.European journal of applied physiology. 06/2014;
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ABSTRACT: Key PointsThe relationship between age and physiological function remains poorly defined and there are no physiological markers that can be used to reliably predict the age of an individual.This could be due to a variety of confounding genetic and lifestyle factors, and in particular to ill-defined and low levels of physical activity.This study assessed the relationship between age and a diverse range of physiological functions in a cohort of highly active older individuals (cyclists) aged 55–79 years in whom the effects of lifestyle factors would be ameliorated.Significant associations between age and function were observed for many functions. was most closely associated with age, but even here the variance in age for any given level was high, precluding the clear identification of the age of any individual.The data suggest that the relationship between human ageing and physiological function is highly individualistic and modified by inactivity.AbstractDespite extensive research, the relationship between age and physiological function remains poorly characterised and there are currently no reliable markers of human ageing. This is probably due to a number of confounding factors, particularly in studies of a cross-sectional nature. These include inter-subject genetic variation, as well as inter-generational differences in nutrition, healthcare and insufficient levels of physical activity as well as other environmental factors. We have studied a cohort of highly and homogeneously active older male (n = 84) and female (n = 41) cyclists aged 55–79 years who it is proposed represent a model for the study of human ageing free from the majority of confounding factors, especially inactivity. The aim of the study was to identify physiological markers of ageing by assessing the relationship between function and age across a wide range of indices. Each participant underwent a detailed physiological profiling which included measures of cardiovascular, respiratory, neuromuscular, metabolic, endocrine and cognitive functions, bone strength, and health and well-being. Significant associations between age and function were observed for many functions. The maximal rate of oxygen consumption ( showed the closest association with age (r = −0.443 to −0.664; P < 0.001), but even here the variance in age for any given level was high, precluding the clear identification of the age of any individual. The results of this cross-sectional study suggest that even when many confounding variables are removed the relationship between function and healthy ageing is complex and likely to be highly individualistic and that physical activity levels must be taken into account in ageing studies.The Journal of Physiology 01/2015; · 4.38 Impact Factor