Year: 2000
Type: article
Abstract: The purpose of this study was to better clarify the VO2 response to exercise to VO2max by comparing data derived from different time averaging intervals and exercise protocols. Sixteen active subjects (12 men and 4 women, mean age, height, weight, and VO2max = 31.6±8.9 yr, 172.0±6.6 cm, 70.8±12.7 kg, 3,212±652 mL/min) completed three different VO2max tests on a cycle ergometer (a 25 Watt/min ramp protocol (R), a 75 Watt/3 min step protocol (S), and a 25 Watt/min ramp protocol (H) under hypoxic conditions (FIO2 = 15%, P B = 635 mm Hg) on separate days. During each test, subjects breathed humidified air from a Tissot tank, and breath-by-breath gas exchange was obtained by a Medical Graphics metabolic cart. All breath-by-breath data were smoothed using an 11-breath moving average. These data were then time-averaged into 15, 30, and 60 s sampling intervals. Criteria for attainment of VO 2max included two of the following: RER ≥ 1.1, maximal heart rate (HR) within 10 b/min of the calculated value, or an O2 plateau (ΔVO2 ≤ 50 mL/min) with an increase in power output. Average VO2max was significantly lower (F (2, 30) = 84.37, p < .001) for the H (2,532±562 mL/min) compared to the S (3,112±660 mL/min) and R (3,212±651 mL/min) protocols. Average maximal RER was significantly different (F (2, 30) = 3.77, p < .05) across protocols, however no differences were exhibited between means. Average HR at VO2max was significantly lower (F (2, 30) = 12.26, p < .001) during the H trial (169±13 b/min) compared to the R (176±9 b/min) and S (178±9 b/min) protocols. The incidence at which subjects demonstrated a plateau in VO2 for all protocols combined were 100, 100, 57 and 8% for the 11 breath, 15 s, 30 s and 1 min averaging, respectively. Data of the change in VO2 between VO2max and the closest neighboring data point revealed that variability was greatest for the longer time averaged data. This response was similar for each protocol. These findings show that shorter sampling intervals (breath-by-breath and 15 s) are most suitable for the detection of the VO2 plateau during progressive exercise to VO 2max. In addition, ramp and step protocols produce similar results, and acute normobaric hypoxia does not decrease the incidence of a VO2 plateau at VO2max using 11 breath or 15 s time averaging procedures.
Language: English
Subfield: Complementary and alternative medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2188867302