Cardiorespiratory Kinetics: Importance of Age, Physical Activity, and Exercise Mode

Objectives: Maximal cardiorespiratory capacity in terms of maximal oxygen uptake (V˙O2max) declines with age. Submaximal exercise parameters, such as the regulation of the cardiorespiratory system (kinetics) as an indicator of cardiorespiratory fitness, seem to be less influenced by age and are preserved by sufficient physical activity. However, kinetics parameters seem to be affected by the habitual type of locomotion in daily life. Hence, kinetics parameters are compared between younger and older adults with similar levels of physical activity for treadmill and cycle ergometry. Methods: 16 younger (28±6 yrs) and 19 older (65±6 yrs) participants were tested on a cycle and treadmill ergometer, respectively. The protocols consisted of randomly changing moderate work rates. Kinetics parameters were assessed via time series analysis. Higher maxima at smaller lags indicate faster kinetics responses. Key results: Time courses for HR kinetics were similar in younger and older adults with equal levels of physical activity (p=0.763), while V˙O2 kinetics were slightly faster for older adults during treadmill but not cycling exercise for several lags (p<0.05). For the older adults, V˙O2 kinetics, but not HR kinetics were faster during treadmill exercise, compared with cycling for several lags (p<0.05), while for the younger adults, faster V˙O2 kinetics were noticed for cycling compared with treadmill exercise for several lags (p<0.05). Conclusion: The type of ergometry seems to be relevant to assess cardiorespiratory kinetics in younger and older adults. This should be considered in clinical practice, after the findings have been evaluated in a frailer group of participants.