Muscle capillarization, O2 diffusion distance, and VO2 kinetics in old and young individuals |
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Authors: | Chilibeck, P. D. Paterson, D. H. Cunningham, D. A. Taylor, A. W. Noble, E. G. |
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Abstract: | Chilibeck, P. D., D. H. Paterson, D. A. Cunningham, A. W. Taylor, and E. G. Noble. Muscle capillarization,O2 diffusion distance, andO2 kinetics in old andyoung individuals. J. Appl. Physiol.82(1): 63-69, 1997.The relationships between muscle capillarization, estimated O2diffusion distance from capillary to mitochondria, andO2 uptake(O2) kineticswere studied in 11 young (mean age, 25.9 yr) and 9 old (mean age, 66.0 yr) adults. O2kinetics were determined by calculating the time constants () forthe phase 2 O2 adjustment to andrecovery from the average of 12 repeats of a 6-min, moderate-intensityplantar flexion exercise. Muscle capillarization was determined fromcross sections of biopsy material taken from lateral gastrocnemius.Young and old groups had similarO2 kinetics(O2-on = 44 vs. 48 s;O2-off = 33 vs. 44 s, for young and old, respectively), muscle capillarization, andestimated O2 diffusion distances.Muscle capillarization, expressed as capillary density or averagenumber of capillary contacts per fiber/average fiber area, and theestimates of diffusion distance were significantly correlated toO2-off kinetics in theyoung (r = 0.68 to 0.83;P < 0.05). We conclude that1) capillarization andO2 kinetics during exerciseof a muscle group accustomed to everyday activity (e.g., walking) arewell maintained in old individuals, and2) in the young, recovery of O2 after exercise isfaster, with a greater capillary supply over a given muscle fiber areaor shorter O2 diffusion distances. |
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