Reliability of forearm oxygen uptake during handgrip exercise: assessment by ultrasonography and venous blood gas.

Assessment of forearm oxygen uptake (V˙O ) 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 (Q˙) and blood gas drawn from a deep forearm vein has been utilized to calculate forearm V˙O for more than two decades, the applicability of this experimental design may benefit from a thorough evaluation of its reliability during graded exercise. Therefore, we evaluated the reliability of this technique during incremental handgrip exercise in ten healthy young (24 ± 3(SD) years.) males. V˙O and work rate (WR) exhibited a linear relationship (1.0 W: 43.8 ± 10.1 mL·min ; 1.5 W: 53.8 ± 14.1 mL·min ; 2.0 W: 63.4 ± 16.3 mL·min ; 2.5 W: 72.2 ± 17.6 mL·min ; 3.0 W: 79.2 ± 18.6 mL·min ; r = 0.65, P < 0.01). In turn, V˙O was strongly associated with Q˙ (1.0 W: 359 ± 86 mL·min ; 1.5 W: 431 ± 112 mL·min ; 2.0 W: 490 ± 123 mL·min ; 2.5 W: 556 ± 112 mL·min ; 3.0 W: 622 ± 131 mL·min ; r = 0.96; P < 0.01), whereas arteriovenous oxygen difference (a-vO ) remained constant following all WRs (123 ± 11-130 ± 10 mL·L ). Average V˙O test-retest difference was -0.4 mL·min with ±2SD limits of agreement (LOA) of 8.4 and -9.2 mL·min , respectively, whereas coefficients of variation (CVs) ranged from 4-7%. Accordingly, test-retest Q˙ difference was 11.9 mL·min (LOA: 84.1 mL·min ; -60.4 mL·min ) with CVs between 4 and 7%. Test-retest difference for a-vO was -0.28 mL·dL (LOA: 1.26mL·dL ; -1.82 mL·dL ) with 3-5% CVs. In conclusion, our results revealed that forearm V˙O determination by Doppler ultrasound and direct venous sampling is linearly related to WR, and a reliable experimental design across a range of exercise intensities.