Intensity and Blood Pressure

The other day, I walked a block at a normal speed on a slight incline as if I were healthy. Soon after,  light-headedness and subdued feeling came over. I checked my blood pressure and the top number was 15 points below normal while the bottom one was off by 5. It lasted for several hours before my blood pressure returned to normal. This is a common occurrence for me with intense activities in a short spurt.