Validity of Breathing Frequency to Monitor Exercise Intensity in Trained Cyclists

This study compared breathing frequency (f_B) during a ventilation threshold (VT) test with f_B during a simulated 40 km time trial (40TT) to assess whether f_B can be used to monitor exercise intensity. Twenty-six male cyclists (X ± SD VO₂max = 4.42 ± 0274 I · min^-1) performed an incremental VT ergometer test and a simulated 40TT on a set of wind-loaded rollers. During the 40TT, expired gas was collected for 3 min using open circuit spirometry at 10 km intervals. A significant correlation (r = 0.89; p < 0.05) was found between the f_B threshold (VT_f) and the gas exchange VT (VT_g) (3.42 ± 0.08 and 3.31 ±0.09 l · min^-1, respectively). No differences were found in VO₂ at the VT_f vs. X VO₂ (3.48 ± 0.08 I · min^-1) during the simulated 40TT. However, when f_B in br · min^-1 calculated from the VT test (32.5 br · min^-1), was compared with f_B during the 40TT (45.6 br · min^-1), there was a significant difference. Ventilation, heart rate and the respiratory exchange ratio were all significantly higher during the 40TT. Although a significant relationship was found between the VT test and the 40TT for VT, measured in I · min^-1 of VO₂ (r = 0.66; p < 0.05), f_B in br · min^-1 obtained from the incremental test should not be used to identify exercise training intensity. These data suggest that during competition, trained athletes exercise at a higher f_B than that determined when being tested, implying that f_B in br · min^-1 may not be a valid measurement of exercise intensity.

Key words

Validity - ventilation threshold - breathing frequency - endurance cyclists - training intensity