IN MALES, AGE 50 YEARS IS WHERE OXYGEN UPTAKE KINETICS START TO CHANGE

Grey, T. M., Spencer, M. D., Murias, J. M., Belfry, G. R., & Paterson, D. H. (2013). The effect of age and training status on VO2 kinetics. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 2482.

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"Although slower oxygen-uptake kinetics is typically observed in older compared to younger adults, the oxygen-uptake kinetics responses across groups of adults of different ages has not been determined. Further, although a speeding of oxygen-uptake kinetics with endurance training is well-established it is not known if age-related slowing of oxygen-uptake kinetics occurs in a similar fashion in well-trained individuals."

This study determined the oxygen-uptake kinetics response across ages in trained cyclists and untrained controls. Trained cyclists and untrained (recreationally active) men, from three age groups were studied: young (18-39 years), middle-aged (40-59 years), and older (60-75 years). Ss completed a ramp incremental cycle ergometer test (20-30 W/minute) to the limit of tolerance (maximal oxygen uptake: VO2max). Subsequently, the time course of adjustment of pulmonary oxygen-uptake was examined from at least three repetitions of step-transitions from 20W to moderate-intensity exercise. Some Ssí data were obtained from previously conducted studies in this laboratory. Pulmonary oxygen-uptake was monitored breath-by-breath using a volume turbine and mass spectrometer in trained young (N = 6), middle-aged (N = 7), and older men (N = 4) and untrained young (N = 8), middle-aged (N = 9), and older (N = 6) men. The on-transient pulmonary oxygen-uptake response was modeled as mono-exponential using non-linear regression.

VO2max showed little change with age for both the untrained and trained groups until ~50 years of age. Thereafter, the rate of decline was 10.2 and 12.3 mL/kg/min per decade. The on-transient pulmonary oxygen uptake response showed little change in untrained controls until ~50 years of age but thereafter increased 11.6 seconds per decade whereas, in the trained group it was not changed (18 seconds) through the middle-ages. Then it showed a modest increase of 3.4 seconds per decade.

Implication. Not until approximately 50 years of age in the untrained group did both the on-transient pulmonary oxygen uptake response increase and VO2max decrease substantially. In contrast, in the trained group, despite the similar age-related decline in VO2max as in the untrained, the slowing of kinetics with age was appreciably less than that of the untrained.

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