Key result
Cycling correlates with ~50% lower SMA blood flow but post-exercise ultrasound lacks long-term reproducibility.
Why the study?
The reproducibility of superior mesenteric artery blood flow measurements before and immediately after exercise using Doppler ultrasound was uncertain.
Is Doppler ultrasound a reproducible method for measuring superior mesenteric artery blood flow before and after exercise in well-trained males?
Observational (n=12)
Is Doppler ultrasound a reproducible method for measuring superior mesenteric artery blood flow before and after exercise in well-trained males?
Duplex scanning of the superior mesenteric artery is not a reproducible method at the individual level for measuring intestinal blood flow immediately after exercise.
Answers are grounded in this paper and cite their sources.
Post-exercise SMA duplex scans lack individual reproducibility; leaves open validated protocols for mesenteric flow assessment in exercise studies.
This study examines the reproducibility of gastro-intestinal blood flow measurements in the superior mesenteric artery (SMA) both before and immediately after exercise with Doppler ultrasound measurements. Twelve well-trained males (mean +/- SD: age 25.9 +/- 3.8 yr; VO2max 4.8 +/- 0.91 x min(-1)) were measured twice (trial 1 and 2) with a 1 week interval before and immediately after 1 hr cycling at 70% VO2max. Duplex scanning was performed with the athletes in supine position immediately after transition from a chair (before exercise) or bicycle (after exercise). The variability of three measurements before exercise was studied within both trials (short-term reproducibility) and the mean pre-exercise values were compared between the trials (long-term reproducibility). In addition, post-exercise measurements were compared in the same way. Reproducibility was tested using the coefficient of variation and Cronbach's alpha. Mean pre-exercise blood flow was 424 +/- 66 ml/min (n = 12) in trial 1 and 375 +/- 38 ml/min (n = 11) in trial 2. Immediately after exercise blood flow had decreased by 49% to 214 +/- 36 ml/min (p <0.01) in trial 1 and by 38% to 234 +/- 36 ml/min (p < 0.01) in trial 2. Blood flow before and after exercise was not significantly different between trials (paired t-test) and therefore reproducible at the group level. Before exercise a good to fair reproducibility was observed both at the short-term (Cronbach's alpha: 0.88 in trial 1, 0.73 in trial 2, n = 11), and at the long-term (alpha = 0.80, n= 11). In contrast, long-term reproducibility immediately after exercise was poor (alpha = -0.99, n = 8 and alpha = 0.36, n = 7 after the first and second cycling period, respectively). In conclusion, duplex scanning of SMA after a sitting-supine transition in well-trained subjects is not a reproducible method at the individual level for intestinal blood flow measurements immediately after exercise.
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Peters et al. (2001) conducted an observational in Healthy (well-trained males) (n=12). 1 hour cycling at 70% VO2max vs. Pre-exercise (baseline) was evaluated on Superior mesenteric artery blood flow (p=<0.01). One hour of cycling at 70% VO2max significantly decreased superior mesenteric artery blood flow, but duplex scanning measurements immediately post-exercise showed poor long-term reproducibility.
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