Stride frequency and ventilation at constant carbon dioxide output.

To determine the consequences of two different stride frequencies on ventilation (VE) at similar levels of carbon dioxide production (VCO2), eleven male subjects performed two work tests on the treadmill. One test involved walking at a speed of 5 km/hr on a 15% grade while the other consisted of running on the treadmill at 9 km/hr on a 0% grade. Running increased stride frequency by 47%. The running and walking tests resulted in similar VCO2 levels, 1.85 +/- .18 and 1.9 +/- .20 l/min respectively, a non-significant difference. Ventilation during running was 43.73 +/- 6.51 l/min and during walking was 43.26 +/- 6.79 l/min, a non-significant difference. In addition the time constants for oxygen consumption (VCO2), VE and VCO2 were measured. The time constants for VCO2 and VE were not found to differ significantly during either the running or walking test. From our results, it can be seen that VE is more closely aligned to the metabolic state rather than stride frequency. In addition, the coupling of VE and VCO2 during the non-steady state is further indicative that ventilation is linked to the metabolic demands of the body.