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Indexed/Abstracted in: BIOSIS Previews, EMBASE, Scopus, Emerging Sources Citation Index
Online ISSN 1827-1812
Ayabe H. 1, 2, Hirakoba K. 2, 3
1 Department of Rehabilitation, Sone Hospital, Saiki, Japan;
2 Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu, Japan;
3 Department of Human Science, Faculty of Computer Science and Systems Engineering, Kitakyushu, Japan
AIM: The aim of this study was to investigate how VO2τ2 in pulmonary oxygen uptake kinetics changes from younger to older adults.
METHODS: Thirty-eight healthy subjects (8 female, 30 male), aged 24-69 yr, were divided into four age groups: 20-39 yr, 40-49 yr, 50-59 yr, 60-69 yr. VO2τ2 on-transient from rest to CLE during cycling was compared between the four groups. Time constant of heart rate (HRτ) during CLE was evaluated as an indirect indicator of oxygen delivery in respiratory and circulatory function.
RESULTS: VO2τ2 was found to be an almost constant value (approximately 30 s) in the first two age groups (20-30s and 40s), but began to slow gradually in the 50s age group (37.3±9.3 s), and was significantly slower (P<0.05) in the 60s age group (48.6±13.5 s) compared to the two younger age groups. Similarly, HRτ revealed a tendency to slow in the 50s age group (53.0±26.3 s), and was significantly slower (P<0.05) in the 60s age group (67.6±23.5 s) compared to the younger group (for this measure the two younger age groups were combined). Our results indicate that VO2τ2 remains at a constant level up to age 50, and then begins to slow gradually.
CONCLUSION: This slowing of VO2τ2 after age of 50 is thought to be due mainly to the decrease in the adaptive rate of the circulatory system and/or reduced oxygen delivery to exercising muscles.