Abstract

The purpose of this study was to determine the effect of a reduced ventilatory frequency (Vf) on blood gases and acid-base changes during three intensities of cycling exercise. VO2max and lactate threshold workload (LaT) of 6 subjects were assessed on a Monark ergometer. Experimental rides were performed 1) with no restriction on Vf (NB) and 2) with a prescribed Vf of 10/min (CFB). Each exercise period consisted of 8 min at 10 of VO2max below the LaT (WI), followed immediately by 8 min at LaT (WII), followed immediately by 8 min at 10 of VO2max above LaT (WIII). At the end of each load blood was analyzed for lactate concentration, pH, PO2, and PCO2. Respiratory exchange was monitored continuously using open circuit indirect calorimetry. Minute ventilation (VE) was significantly reduced by CFB at all three workloads. The reduced VE resulted in lower blood PO2 at each workload, however, neither blood lactate nor VO2 were significantly different between CFB and NB for the three loads. Blood (H+) was significantly higher in CFB than NB at all three loads with the greatest difference between trials at WIII (NB: 37.93+/-0.68 nM; CFB: 44.77+/-1.02 nM). This was accounted for by a significantly higher PCO2 during CFB in WII and WIII (WII, NB: 33.0+/-1.4 mmHg, CFB: 35.7+/-2.7 mmHg; WIII, NB: 31.2+/-1.7 mmHg, CFB: 38.9+/-2.4 mmHg). It is concluded that a reduction in breathing frequency during exercise caused respiratory acidosis at exercise intensities that were not associated with (H+) disturbance during normal ventilation. Verf.-Referat