In timing your swim to determine your optimal aerobic training pace, you will need a pace clock and a friend with a lap counter to keep track of the distance you have covered. Immediately after ceasing exercise, count your pulse for 10 seconds and compare with your target rate. By comparing your pulse rate with elapsed exercise time and target rate, you can judge the intensity of your workout. Two minutes later another check of your pulse should show considerable recovery — a 10-second count of less than 20 is desirable.
