Ventilatory responses of trained and untrained subjects during running and walking

To investigate the influence of stride frequency on ventilation in different subject populations, the ventilatory responses to walking and running at similar metabolic loads were studied in 29 males. Ten of the males were well-trained, highly fit runners (HFR), ten were well-trained, highly fit cyclists (HFC), and nine were healthy low-fit males (LFM) who did not engage in any form of regular exercise. All subjects completed two separate exercise bouts, a level run and an uphill walk, at 90% of their ventilatory threshold. Stride frequency was found to increase by 49% between the walk and run trials. Minute ventilation (VE), tidal volume (VT), breathing frequency (f), end-tibial CO2 tension (PETCO2), end-tidal O2 tension (PETO2), and inspiratory time (TI) were all significantly different (P less than 0.05) between the walk and run trials for the HFR. Minute ventilation and expiratory time (TE) did not differ significantly between the walk and run trials for the HFC; however, VT, f, PETCO2, PETO2, and TI were significantly different. Only PETCO2 and TI were found to be significantly different between the walk and run trials for the LFM. These results suggest that stride frequency affects ventilation to varying degrees dependent upon the subject population and that the mechanisms for the hyperpnea of moderate exercise operating in each of these subject populations involve a complex interaction of many factors.