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

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; 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 ( V ˙ o2max/ 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% V ˙ o2peak) oxygen uptake ( V ˙ o2) values at GET1 with those obtained at fRT1, nor between V ˙ o2 values at GET2 with those at fRT2 (76-78% V ˙ o2peak). Heart rate (HR) at fRT1, and 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 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 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.