Maximal strength training and increased work efficiency: contribution from the trained muscle bed

Barrett-O'Keefe Z, Helgerud J, Wagner PD, Richardson RS. Maximal strength training and increased work efficiency: contribution from the trained muscle bed. J Appl Physiol 113: 1846-1851, 2012. First published September 13, 2012; doi: 10.1152/japplphysiol.00761.2012.-Maximal strength training (MST) reduces pulmonary oxygen uptake ((V) over dotO(2)) at a given submaximal exercise work rate (i.e., efficiency). However, whether the increase in efficiency originates in the trained skeletal muscle, and therefore the impact of this adaptation on muscle blood flow and arterial-venous oxygen difference (a-vO(2diff)), is unknown. Thus five trained subjects partook in an 8-wk MST intervention consisting of half-squats with an emphasis on the rate of force development during the concentric phase of the movement. Pre- and posttraining measurements of pulmonary (V) over dotO(2) (indirect calorimetry), single-leg blood flow (thermodilution), and single-leg a-vO(2diff) (blood gases) were performed, to allow the assessment of skeletal muscle (V) over dotO(2) during submaximal cycling [237 +/- 23 W; similar to 60% of their peak pulmonary (V) over dotO(2) ((V) over dotO(2peak))]. Pulmonary (V) over dotO(2peak) (similar to 4.05 l/min) and peak work rate (similar to 355 W), assessed during a graded exercise test, were unaffected by MST. As expected, following MST there was a significant reduction in pulmonary (V) over dotO(2) during steady-state submaximal cycling (similar to 237 W: 3.2 +/- 0.1 to 2.9 +/- 0.1 l/min). This was accompanied by a significant reduction in single-leg (V) over dotO(2) (1,101 +/- 105 to 935 +/- 93 ml/min) and single-leg blood flow (6,670 +/- 700 to 5,649 +/- 641 ml/min), but no change in single-leg a-vO(2diff) (16.7 +/- 0.8 to 16.8 +/- 0.4 ml/dl). These data confirm an MST-induced reduction in pulmonary (V) over dotO(2) during submaximal exercise and identify that this change in efficiency originates solely in skeletal muscle, reducing muscle blood flow, but not altering muscle a-vO(2diff).