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

Assessment of forearm oxygen uptake ([Formula: see text] O(2)) 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 ([Formula: see text]) and blood gas drawn from a deep forearm vein has been utilized to calculate forearm [Formula: see text] O(2) 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. [Formula: see text] O(2) and work rate (WR) exhibited a linear relationship (1.0 W: 43.8 ± 10.1 mL·min(−1); 1.5 W: 53.8 ± 14.1 mL·min(−1); 2.0 W: 63.4 ± 16.3 mL·min(−1); 2.5 W: 72.2 ± 17.6 mL·min(−1); 3.0 W: 79.2 ± 18.6 mL·min(−1); r = 0.65, P < 0.01). In turn, [Formula: see text] O(2) was strongly associated with [Formula: see text] (1.0 W: 359 ± 86 mL·min(−1); 1.5 W: 431 ± 112 mL·min(−1); 2.0 W: 490 ± 123 mL·min(−1); 2.5 W: 556 ± 112 mL·min(−1); 3.0 W: 622 ± 131 mL·min(−1); r = 0.96; P < 0.01), whereas arteriovenous oxygen difference (a‐vO(2diff)) remained constant following all WRs (123 ± 11–130 ± 10 mL·L(−1)). Average [Formula: see text] O(2) test–retest difference was −0.4 mL·min(−1) with ±2SD limits of agreement (LOA) of 8.4 and −9.2 mL·min(−1), respectively, whereas coefficients of variation (CVs) ranged from 4–7%. Accordingly, test–retest [Formula: see text] difference was 11.9 mL·min(−1) (LOA: 84.1 mL·min(−1); −60.4 mL·min(−1)) with CVs between 4 and 7%. Test–retest difference for a‐vO (2diff) was −0.28 mL·dL(−1) (LOA: 1.26mL·dL (−1); −1.82 mL·dL(−1)) with 3–5% CVs. In conclusion, our results revealed that forearm [Formula: see text] O(2) determination by Doppler ultrasound and direct venous sampling is linearly related to WR, and a reliable experimental design across a range of exercise intensities.