Blood flow response to treadmill running in the rat spinotrapezius muscle.

The rat spinotrapezius muscle has been utilized to investigate the microcirculatory consequences of exercise training. It was the purpose of this investigation to determine whether, and to what extent, this muscle is recruited during treadmill exercise. Radioactive 15-micron microspheres were used to measure blood flow to the spinotrapezius and hind limb musculature as well as to the abdominal organs of female Wistar rats. Blood flows were measured at rest and during two levels of treadmill-running exercise (i.e., 0% grade, 15 m/min and 10% grade, 24 m/min). As expected, exercise increased blood flow to the soleus, plantaris, red gastrocnemius, mixed gastrocnemius, and white gastrocnemius muscles, whereas blood flow to the stomach, intestines, pancreas, spleen, and kidneys was decreased (P < 0.05). However, contrary to our expectation, blood flow to the spinotrapezius muscle decreased from 61 +/- 6 ml.100 g-1.min-1 at rest to 39 +/- 2 ml.100 g-1.min-1 at 0% grade, 15 m/min and 46 +/- 4 ml.100 g-1.min-1 at 10% grade, 24 m/min (P < 0.05). These findings support the premise that treadmill running does not recruit the spinotrapezius muscle and suggest that previous training-induced arteriolar adaptations produced in this muscle may result from mechanisms unrelated to augmented exercise blood flow or muscle metabolism.