swollen feet
Pumped,
Swollen feet and ankles occur when blood and interstitial fluids pool in the soft tissues of lower extremities.
This can result from many factors but one of the reasons is due to lack of blood return.
The large vains in the lower extremities have one way valves to assist blood in the return to the heart. The normal contractions of the large muscles in the legs act as the pumping mechanism to assist the valves in blood return.
My guess is your legs are not used to being worked in a way that requires a large blood flow with minimal change in muscle range of motion.
Once you have started walking on the treadmill by prior to the swelling, try getting off the treadmill and stretching the larger muscles of lower extremities through full range of motion to assist in blood return. This should help.
Also, check your blood pressure.
It will probably just take some time for your body get used to it.
Good luck,
B.D.