Aerobic exercise improves the efficiency of your heart, blood vessels
and lungs. Swimming is an excellent aerobic exercise because it strengthens
your entire cardiovascular system. Studies have shown that aerobic
workouts strengthen a swimmer's heart, increase the number of blood
vessels and increase lung size and capacity.
Swimming has another special benefit. Because you are in a horizontal
position, you experience less gravitational pull. Also, when immersed
in water, your heart increases slightly in size, known as the "diving
reflex." Combined, these result in 10% to 20% more blood pumped through
your body with every heartbeat. You can actually work harder and longer
in water than on land.
Pulse rate is a good indication of how hard you are exercising. As outlined
by Harvey S. Wiener in Total Swimming, your Target Zone is the heart rate
you need to experience the maximum aerobic conditioning. To calculate
your heart's Target Zone, first subtract your age from 220. This gives
your Maximum Pulse Rate or MPR. If in good condition, your Target Zone
should be between 70 and 80% of your MPR.
For swimming to enhance fitness, maintain a pulse rate in your Target
Zone for 20 to 30 minutes three times a week. As you train and improve
your cardiovascular conditioning, it will take more effort to reach your
Target Zone. More advanced techniques like Interval Training involve short,
fast swims broken up by brief rest periods. Of course, before starting any
swimming or water exercise program, check with your doctor.
