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A comparison of blood flow of the vastus lateralis during exercise in trained and untrained cyclists as measured by 133 Xenon clearance

University of British Columbia

The purpose of this investigation was to examine muscle blood flow (MBF) in the vastus lateralis of trained and untrained cyclists using the ¹³³Xenon clearance method. MBF was measured in five trained cyclists (V02max = 68.8 ± 4.2 ml/kg/min) and five untrained subjects (V02max = 48.2 ± 4.2 ml/kg/min) at 150 Watts, the anaerobic threshold (AT), and at 100% V02max. These workloads corresponded to an absolute (150 W), relative (AT) and maximal comparison between groups. ¹³³Xenon dissolved in saline (3-9 MBq in < 0.2 ml volume), was injected in the vastus lateralis muscle prior to ergometer work. Clearance of the isotope was monitored using a gamma camera positioned adjacent to the injection site (Chung et. al., 1987). MBF calculations are based on the half clearance time (T1/2) during the initial steep portion of the clearance curve, and the blood-muscle partition coefficient value of ¹³³Xenon (0.7) according to the formula MBF = (In 2/T1/2) * 0.7 * 100 (Clausen and Lassen, 1971). MBF was not significantly different between the two groups at 150 Watts (28.7 ± 3.7 vs. 27.5 ± 7.9 ml/100g/min for trained and untrained groups respectively) or at AT (35.1 ± 8.6 vs. 29.8 ± 2.6 ml/100g/min), but was significantly higher in the trained group at 100% V02max (35.6 ± 8.1 vs. 27.0 ± 4.3 ml/100g/min). It appears that the high variability in the MBF results may have masked some differences, thereby identifying this limitation in the gamma camera technique. No significant differences were evident across the three exercise conditions in either group, and no significant relationships were detected between MBF and workload (expressed in Watts, ml of oxygen, or % V02max). The lack of a strong correlation between workload and MBF indicates that the technique may not accurately track MBF across all exercise intensities. It appears that the gamma camera technique may not be suitable for measuring MBF at high exercise intensities due to the short time course of ¹³³Xenon washout.

Thesis/Dissertation

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2009-05-19

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http://hdl.handle.net/2429/7949

Human Kinetics

University of British Columbia

UBCV

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