A new objective method for determining exercise gas exchange thresholds by respiratory frequency in middle-aged men

Abstract

Abstract Purpose To evaluate the agreement between the two Gas Exchange Thresholds (GETs = GET1 and GET2), identified by the conventional V-Slope method, and two Respiratory Frequency Thresholds (fRTs = fRT1 and fRT2) obtained from a novel, low-cost, and simple method of breakpoint determination. Methods Fifty middle-aged males (age: 50–58 years; $$\dot{V}$$ V ˙ o2peak: 37.5 ± 8.6 mL·Kg−1·min−1), either healthy or with chronic illnesses, underwent an incremental cycle exercise test to determine maximal oxygen uptake ($$\dot{V}$$ V ˙ o2max/$$\dot{V}$$ V ˙ o2peak), GETs and fRTs. Results There were no statistical differences [P > 0.05; ES: 0.17 to 0.32, small] between absolute and relative (56–60% $$\dot{V}$$ V ˙ o2peak) oxygen uptake ($$\dot{V}$$ V ˙ o2) values at GET1 with those obtained at fRT1, nor between $$\dot{V}$$ V ˙ o2 values at GET2 with those at fRT2 (76–78% $$\dot{V}$$ V ˙ o2peak). Heart rate (HR) at fRT1, and $$\dot{V}$$ V ˙ o2 and HR at fRT2 showed very large correlations (r = 0.75–0.82; P < 0.001) and acceptable precision (SEE < 7–9%) in determination of their corresponding values at GET1 and GET2. The precision in the estimation of $$\dot{V}$$ V ˙ o2 at GET1 from fRT1 was moderate (SEE = 15%), while those of power output at GET1 (SEE = 23%) and GET2 (SEE = 12%) from their corresponding fRTs values were very poor to moderate. Conclusion HR at fRT1 and $$\dot{V}$$ V ˙ o2 and HR at fRT2, determined using a new objective and portable approach, may potentially serve as viable predictors of their respective GETs. This method may offer a simplified, cost-effective, and field-based approach for determining exercise threshold intensities during graded exercise.