YOU WEIGH MORE AFTER A WORKOUT BECAUSE ,YOUR MUSCLES EXPAND TO COPE WITH THE EXTRA BLOOD FLOW. ALSO,EVEN THOUGH YOU ARE LOSING SOME FLUIDS DURING CARDIOVASCULAR ACTIVITY, YOU USUALLY ARE DRINKING TO REPLACE MORE THAN YOU HAVE LOST . WITH MUSCLE EXPANSION AND INCREASED FLUID INTAKE YOU WILL WEIGH SEVERAL POUNDS MORE AFTER A WORKOUT. USUALLY THE EXTRA POUNDS GO AWAY IN A COUPLE OF HOURS.