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Examination of the relationship between the slow component of oxygen uptake kinetics and plasma ammonia concentrations during cycle ergometer exercise

Moh H Malek, University of Nebraska - Lincoln

Abstract

The purposes of this study were to: (1) compare the patterns of responses for plasma ammonia concentration ([NH3]) during moderate- and heavy intensity cycle ergometry; and (2) examine the relationship between the V˙O2 slow component (V˙O2SC) and plasma [NH3]. Thirteen healthy, untrained college males who performed less than a total of two hours of aerobic and/or resistance exercise per week visited the laboratory on six separate occasions. The initial visit included a V˙O2max test, whereas subsequent visits involved constant power output exercise (7-minutes in duration) at two different intensities [moderate 60%GET = 60% of the gas exchange threshold; and heavy, Δ50% = 50% of the difference between GET and V˙O2max)]. Plasma was collected from an antecubital vein prior to the exercise, during the last three minutes of the six minute warm-up, and during each minute of the seven minute constant power output workbout. The time course of changes in plasma [NH3] and V˙O2 during the two constant power output exercise intensities (60%GET and Δ50%) were assessed separately using 2 (intensity: 60%GET and Δ50%) × 7 (time: each minute of 7-minute workbout) repeated-measures ANOVAs. When appropriate, Scheffé's post-hoc analyses were used to determine significantly different mean values. In addition, a Pearson's correlation coefficient was calculated to assess the relationship between plasma [NH3] and the amplitude of the V˙O2SC for the heavy intensity exercise. For moderate intensity exercise (60%GET), there were no significant differences in the mean normalized plasma [NH3] during the 7-minute workbout. In addition, the mean normalized V˙O2 values were not significantly different from each other during the final 5-minutes of the exercise workbout. For heavy intensity exercise (Δ50%), there was a significant increase in the mean normalized plasma [NH3] during the 7-minute workbout. Similarly, the mean normalized V˙O 2 response increased significantly during the entire 7-minute workbout. Pearson's correlation coefficient indicated a significant (r = 0.76, p < 0.05) relationship between [NH3]Δ7-3 (the difference in normalized [NH3] between the 7 th- and 3rd-minute ([NH3]Δ7-3 ) of the Δ50% constant power output exercise) and the V˙O2SC amplitude. The results indicated that during moderate intensity exercise, the V˙O2 response reached a steady-state with no change in plasma [NH3] from baseline values. For the heavy intensity exercise, however, there was a V˙O 2SC and plasma [NH3] increased continuously until the end of exercise. These findings suggest a potential relationship between exercise-induced increase in plasma [NH3] and the V˙O 2SC during heavy intensity exercise.^

Subject Area

Health Sciences, Recreation|Biology, Physiology

Recommended Citation

Malek, Moh H, "Examination of the relationship between the slow component of oxygen uptake kinetics and plasma ammonia concentrations during cycle ergometer exercise" (2007). ETD collection for University of Nebraska - Lincoln. AAI3252440.
http://digitalcommons.unl.edu/dissertations/AAI3252440

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