false,
immune system boost last as long as the exercise its no different then any aerobic exercise its a result of the increase in blood pressure and heart rate, and of course the opposite occurs after its over the blood pressure and heart rate plummet as you relax and so does the immune system.
and of course you spend more time in relax mode then you did exercising so the overall average effect is actually immune system suppression, but the study doesnt factor in anything other then during the exercise,