Respiratory responses to running and walking at the same metabolic rate

The ventilatory responses of ten subjects were evaluated during walking and running on a motor driven treadmill. The treadmill grade was adjusted so that the oxygen uptake was the same walking as running at 0% grade. Ventilation (gasometer) and PETCO2 (infrared CO2 analyzer) were monitored breath-by-breath. It was found that running, compared to uphill walking, significantly increased ventilation by an average of 7.80 1 X min-1 BTPS. Respiratory frequency increased by approximately 27% while tidal volume was reduced by an average of 7.2%. The R value of running was 0.88, significantly greater than the 0.81 calculated for uphill walking. Walking resulted in a mean PETCO2 of 46.9 +/- 0.8 Torr, while running significantly reduced the PETCO2 by 4.3 +/- 0.4 Torr. The time components of the breathing cycle were also different for walking and running. These results suggest that by changing gait, at a constant metabolic cost, a dissociation VCO2 and VO2 may occur. These results also suggest a variation in the control of respiration when comparing walking and running.