A nomogram for assessment of breathing patterns during treadmill exercise

Objective: To assess the breathing patterns of trained athletes under different conditions. The hypothesis is that the breathing pattern during a progressive treadmill exercise is independent of the protocol, at least in healthy people, and can be assessed using a nomogram. Methods: A total of 43 male and 21 female athletes from different sports were studied. They performed one of two different protocols (steps or ramp) on a treadmill. The two protocols started at the same speed and had the same rate of increase in work. During the test, the expired air was analysed for CO2 and O-2. Ventilation (VE) was continuously recorded, and tidal volume (Vt) and breathing frequency (BF) at the same intensity were analysed for both protocols, as well as Vt/T-i and T-i/T-tot. Results: No significant differences were observed in Vt and BF between the two protocols in either the men or women at any level (confidence intervals up to 0.958 in all the groups). T-i/T-tot remained constant, and all increases in VE were strongly related to the respective increases in Vt/T-i. Plots of data for men and women showed a curvilinear relation between Vt and BF which could be fitted with an exponential function with a strong correlation (R-2 = 0.98 for men and 0.97 for women). Conclusions: Graphic expression of Vt v BF is a useful nomogram for the routine assessment of ventilatory response during exercise in healthy trained subjects.