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Effects of Controlled Frequency Breathing During Exercise on Blood Gases and Acid-Base Balance
14 March 2008 (online)
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. V̇O2max and lactate threshold workload (LaT) of six 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 V̇O2max below the LaT (WI), followed immediately by 8 min at LaT (WII), followed immediately by 8 min at 10% of V̇O2max above LaT (WIII). Blood was taken from a heated fingertip at the end of each load and analyzed for lactate concentration, pH, PO2, and PCO2. Respiratory exchange was monitored continuously using open circuit indirect calorimetry. Minute ventilation (V̇E) was significantly reduced by CFB at all three workloads. The reduced VE resulted in lower (p < 0.05) blood PO2at each workload (p < 0.05), however, neither blood lactate nor V̇O2 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.
Hydrogen ion - hypercapnia - respiratory acidosis - tidal volume - ventilation