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 (fTs = fT1 and fT2) obtained from a novel, low-cost, and simple method of breakpoint determination.

METHODS

Fifty middle-aged males (age: 50-58 years; o: 37.5 ± 8.6 mL·Kg·min), either healthy or with chronic illnesses, underwent an incremental cycle exercise test to determine maximal oxygen uptake ( o/ o), GETs and fTs.

RESULTS

There were no statistical differences [P > 0.05; ES: 0.17 to 0.32, small] between absolute and relative (56-60% o) oxygen uptake ( o) values at GET1 with those obtained at fT1, nor between o values at GET2 with those at fT2 (76-78% o). Heart rate (HR) at fT1, and o and HR at fT2 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 o at GET1 from fT1 was moderate (SEE = 15%), while those of power output at GET1 (SEE = 23%) and GET2 (SEE = 12%) from their corresponding fTs values were very poor to moderate.

CONCLUSION

HR at fT1 and o and HR at fT2, 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.