The purpose of this investigation was to examine the change in pulmonary ventilation (V_E), ventilatory equivalent of oxygen (VE_O_2) and lactic acid (LA) in relation to oxygen uptake (V_O_2) as predictors of the lactate threshold (LT). Eight healthy male (21.9 ± 3.0 years) subjects conducted three incremental-load tests. In each test the initial work rate consisted of 4 minutes of unloaded pedaling ("0" load) followed by incremental-load work of 360 Kgm • min^-1 at 60 rpm for trial I and trial II, while during trial III the work rate consisted of 540 Kgm • min^-1 of incremental-load work at 90 rpm. Work load was increased every third minute until the subject reached voluntary exhaustion. Blood samples from a forearm vein were collected during trial II (60 rpm) and trial III (90 rpm) and analyzed for lactic acid. In our subjects the measured (x̄ ± SD) lowest VE_O_2 for O_2 in relation to V_O_2 for trial I of 22.9 ± 1.9 occurred at a V_O_2 of 1.27 ± 0.8 L • min^-1. For trial II the VE_O_2 of 22.4 ± 1.3 occurred at a V_O_2 of 1.30 ± 0.09 L • min^-1, while for trial III a VE_O_2 of 24.4 ± 2.5 occurred at a V_O_2 of 1.84 ± 0.15 L • min^-1. The lowest VE_O_2 and onset of LA accumulation as calculated from individual exponential equations relating V_E to V_O_2 yielded V_O_2 values at 1.77 ± 0.18 L • min^-1 and 1.74 ± 0.25 L • min^-1 for trial II, and 1.83 ± 0.19 L • min^-1 and 2.02 ± 0.53 during trial III. Utilizing ln[LA]-ln V_O_2 equations, the LT occurred at a V_O_2 of 1.30 ± 0.07 L • min^-1 during trial II and 1.85 ± 0.12 L • min^-1 during trial III. It was concluded that during the 60 rpm test that the lactate threshold was best predicted by measured lowest VE_O_2 and the plot of the In[LA] to In V_O_2 relationship. The methods used in this study provide a valid and reliable estimate of the lactate threshold and support the use of measured lowest VE_O_2 , a respiratory gas exchange measure, as an indirect measure of the lactate threshold.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc331769 |
| Date | 12 1900 |
| Creators | Duvillard, Sergei Petelin von. |
| Contributors | Miller, James R., Patton, Robert W., Hagan, Raymond Donald |
| Publisher | North Texas State University |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | xi, 140 leaves : ill., Text |
| Rights | Public, Duvillard, Sergei Petelin von., Copyright, Copyright is held by the author, unless otherwise noted. All rights reserved. |
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