XXXX release is higher across arm than leg muscles during whole-body exercise.

@entity1 @entity650 @entity844 @entity455 @entity1009 @entity26 @entity880 @entity413
Exercising muscle releases @entity650 ( @entity650 ), but the mechanisms controlling this process are poorly understood. This study was performed to test the hypothesis that the @entity650 release differs in arm and leg muscle during whole-body exercise, owing to differences in muscle metabolism. Sixteen subjects (10 @entity1 and six @entity1 , with body mass index 24    1 kg m(-2) and peak @entity26 uptake 3.4    0.6 l @entity1009 )) performed a 90 min combined arm and leg cycle exercise at 60% of maximal @entity26 uptake. The subjects arrived at the laboratory having fasted overnight, and catheters were placed in the femoral artery and vein and in the subclavian vein. @entity455 was sampled and arm and leg blood flow were measured by thermodilution. Lean limb mass was measured by dual-energy X-ray absorbtiometry scanning. Before and after exercise, biopsies were obtained from vastus lateralis and deltoideus. During exercise, @entity650 release was similar between @entity1 and @entity1 and higher (P < 0.05) from arms than legs (1.01    0.42 and 0.33    0.12 ng @entity1009 ) (kg lean limb mass)(-1), respectively). Blood flow (425    36 and 554    35 ml @entity1009 ) (kg lean limb mass)(-1)) and @entity844 uptake (26    7 and 47    7  mol @entity1009 ) (kg lean limb mass)(-1)) were lower, @entity413 uptake similar (51    12 and 41    8 mmol @entity1009 ) (kg lean limb mass)(-1)) and @entity880 release higher (82    32 and -2    12  mol @entity1009 ) (kg lean limb mass)(-1)) in arms than legs, respectively, during exercise (P < 0.05). No correlations were present between @entity650 release and exogenous substrate uptakes. Muscle glycogen was similar in arms and legs before exercise (388    22 and 428    25 mmol (kg dry weight)(-1)), but after exercise it was only significantly lower in the leg (219    29 mmol (kg dry weight)(-1)). The novel finding of a markedly higher @entity650 release from the exercising arm compared with the leg during whole-body exercise was not directly correlated to release or uptake of exogenous substrate, nor to muscle glycogen utilization.
