Can high intensity workloads be simulated at moderate intensities by reduced breathing frequency

Objectives: This study was designed to investigate whether reduced breathing frequency during moderate intensity exercise produces similar metabolic responses as during exercise with spontaneous breathing at higher absolute intensity. Methods: Eight healthy male subjects performed a constant load test with reduced breathing frequency at 10 breaths per minute to exhaustion (B10) at the peak power output obtained during the incremental test with RBF (peak power output increased every two minutes for 30 W). The subjects then performed a constant load test with the spontaneous breathing to exhaustion (SB) at peak power output obtained during the incremental test with spontaneous breathing. Results: Respiratory parameters (V E, PETO2, PETCO2), metabolic parameters (V O2, V · CO2) and oxygen saturation (SaO2) were measured during both constant load tests. Capillary blood samples were taken before and every minute during both constant load tests in order to measure lactate concentration ([LA-]) and parameters of capillary blood gases and acid base status (PO2, PCO2, pH). Regardless of the type of comparison (the data obtained at the defined time or maximum and minimum values during the exercise), there were significant differences between SB and B10 in all respiratory parameters, metabolic parameters and SaO2 (p ≤ 0.01 and 0.05). There were significantly lower [LA-] and PCO2 during B10, when compared to SB (p≤0.01). However, there were no significant differences in pH during the exercise between different breathing conditions. Conclusion: It can be concluded that reduced breathing frequency during exercise at lower absolute intensity did not produce similar conditions as during the exercise with spontaneous breathing at higher absolute intensity. KEY WordS: reduced breathing frequency, respiratory acidosis, constant load exercise In some previous studies, swimmers reduced their breathing frequency during tethered front crawl swimming [3, 24, 29], during front crawl interval sets [8], during front crawl swimming at OBLA velocity [13] and during maximal front crawl swimming [14]. These studies were unable to demonstrate hypoxia conditions by analysing the air expired during the exercise [3, 8, 29] or by measuring capillary blood sampled after the exercise [13, 14]. Considering the obtained higher partial pressure of CO2, they concluded that this kind of training is more likely hypercapnic training. Due to the technical limitations of measuring respiratory and blood parameters during swimming, the idea of RBF during exercise on land has been also investigated; examples include cycle ergometry [12, 25, 32] and treadmill running [21]. These studies confirmed marked hypercapnia as result of RBF during exercise. In addition, they also obtained hypoxia by measuring capillary blood sampled and oxygen saturation (SaO2) during exercise with RBF. All of the reported studies compared the subjects’ response during exercise with different breathing conditions (spontaneous and RBF) at the same absolute intensity. However, the question is whether RBF during moderate Original Pap r Biol. Sport 2010;27:163-168