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

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 (f R Ts = f R T1 and f R T2) obtained from a novel, low-cost, and simple method of breakpoint determination. Methods Fifty middle-aged males (age: 50–58 years; V̇ V ˙ o 2peak : 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 ( V̇ V ˙ o 2max / V̇ V ˙ o 2peak ), GETs and f R Ts. Results There were no statistical differences [ P > 0.05; ES: 0.17 to 0.32, small ] between absolute and relative (56–60% V̇ V ˙ o 2peak ) oxygen uptake ( V̇ V ˙ o 2 ) values at GET1 with those obtained at f R T1, nor between V̇ V ˙ o 2 values at GET2 with those at f R T2 (76–78% V̇ V ˙ o 2peak ). Heart rate (HR) at f R T1, and V̇ V ˙ o 2 and HR at f R T2 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 V̇ V ˙ o 2 at GET1 from f R T1 was moderate (SEE = 15%), while those of power output at GET1 (SEE = 23%) and GET2 (SEE = 12%) from their corresponding f R Ts values were very poor to moderate . Conclusion HR at f R T1 and V̇ V ˙ o 2 and HR at f R T2, 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.