Validity Of Forearm Oxygen Uptake During Handgrip Exercise

Assessment By Ultrasonography And Venous Blood Gas

294 Board #115 May 31 11

00 AM - 12

30 PM

ABSTRACT: Assessment of forearm oxygen uptake (V[Combining Dot Above]O₂) during handgrip exercise is a keenly investigated concept for observing small muscle mass metabolism. Although a combination of Doppler-ultrasound measurements of brachial artery blood flow and blood gas drawn from a deep forearm vein has been utilized to calculate forearm V[Combining Dot Above]O₂ for more than two decades, this experimental design has, somewhat surprisingly, not been validated.

PURPOSE: To evaluate the reliability and accuracy of this technique following handgrip exercise.

METHODS: Test-retest measurements were performed with ~0.25 watt (W) steady state increments in ten healthy young (24±3(SD) yrs.) males during handgrip exercise.

RESULTS: V[Combining Dot Above]O₂and workload exhibited a linear relationship(p<0.01)following all submaximal workloads (0.50W:43.8±10.1mL·min^-1; 0.75W:53.8±14.1mL·min^-1;1.00W:63.4±16.3mL·min^-1;1.25W:72.2±17.6mL·min^-1), while the final increment before exhaustionwas non-significant, marking a V[Combining Dot Above]O₂-plateau (1.5W:79.2±18.6mL·min^-1). In turn, blood flow exhibited a concomitant relationship (p<0.01) with V[Combining Dot Above]O₂(0.50W:359±86mL·min^-1; 0.75W:431±112mL·min^-1; 1.00W:490±123mL·min^-1; 1.25W:556±112mL·min^-1; 1.50W:622±131mL·min^-1) while arteriovenous oxygen difference (a-vO_2diff) remained constant following all workloads (123±11-130±10mL·L^-1).The average V[Combining Dot Above]O₂test-retest difference was -0.4mL·min^-1 with ±2SD limits of agreement (LOA) of 8.4 and -9.2mL·min^-1, respectively, while coefficients of variation (CV) ranged from 4-7%. Accordingly, test-retest blood flow difference was 11.9mL·min^-1(LOA:84.1mL·min^-1; -60.4mL·min^-1) andagain CV ranged between 4-7%. Test-retest difference for a-vO_2diff was -0.28mL·dL^-1(LOA: 1.26mL·dL^-1; -1.82mL·dL^-1) with CV ranging from 3-5%.

CONCLUSION: Our results reveal that forearm V[Combining Dot Above]O₂-assessment by Doppler-ultrasound and direct venous sampling is a valid experimental design across a range of exercise intensities, and suggest that this method can be applied for assessment of small muscle mass metabolism in occupationally relevant forearm musculature.