Effects of Controlled Frequency Breathing During Exercise on Blood Gases and Acid-Base Balance

 

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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. 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 (V̇_E) was significantly reduced by CFB at all three workloads. The reduced V_E 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.