this is very common during exercise particularly during walking and especially so when it gets hot and humid. fluid tends to accumulate in the extremities as the result of the arm swing and holding arms straight. it can be bad enough that people need to remove their rings before exercising. one solution is that every few minutes raise your hands over your head and clench and relax your hands. some people will carry a squeeze ball which keeps the blood and other fluids flowing in and out of the hands. you can also hold your arms at 90 degrees and use a race-walk style arm swing.
when i walk for exercise my fingers tend to swell and get numb. why does this happen?