Exercise-entrained breathing and non-invasive determination of anaerobic threshold

Incremental cycle exercise was performed by 17 subjects under two breathing conditions: spontaneous breathing (Non-ENT run) and deliberate entrainment of breathing frequency (f) to cycling rate at preferred coupling ratios up to possibly high work rates (ENT run). The purpose was to investigate the influence of entrainment on two non-invasive determinations of anaerobic threshold (AT): the break points of VE/VO2 (VAT) and VCO2 (V-slope AT) changes against VO2. Compared to the Non-ENT run, VAT in the ENT run was greater in 12 subjects entrained at higher f accompanied by relative hyperventilation at low work rates, while it was similar in five subjects entrained at lower f accompanied by relative hypoventilation. Relative hyperventilation and hypoventilation during the ENT run tended to elicit greater and lower VCO2, respectively, relative to VO2, as compared to the Non-ENT run. These different VCO2, responses between the two runs exerted little influence on the V-slope AT determination. It is concluded that breathing patterns and ventilatory response during incremental work tests can affect the VAT method but not the V-slope method.