The effect of venous obstruction on effort tolerance is not well. appr
eciated. We studied a patient with severe lower body venous obstructio
n (with near normal heart and lung function) who had marked exercise i
ntolerance. Peak O-2 uptake for leg exercise ,vas reduced, but peak O-
2 uptake for upper extremities was normal. This difference indicates t
hat severe venous obstruction can lead to exercise limitation.