Blood volume changes are controlled centrally not locally - A near-infrared spectroscopy study of one legged aerobic exercise

It is well known that blood flow increases in an exercising limb to match increases in oxygen consumption. However, it is less clear what effects occur in the opposite limb. We performed a one legged incremental cycling protocol and used near-infrared spectroscopy to measure changes in muscle blood volume and oxygenation in the exercising and non-exercising leg. As expected during exercise the exercising leg was deoxygenated relative to the non-exercising leg. However, there were similar increases in blood volume to both legs during the exercise, and during the post-exercise recovery period similar volume and oxygenation increases were seen in both legs. We conclude that blood volume increases may be signalled locally, but the effect is expressed globally. Previous studies have demonstrated a training effect in the non-exercising leg following one legged aerobic exercise. The large haemodynamic changes in the non-exercising leg observed here may be partially responsible for the cross-training effect.