How to plan workouts!
When I travelled to Ontario I visited my brother Thurlow who wrote a program based on the German science of training. With this program you ad the resting heart rate, your age, and the time you want to swim for 25, 50, 75, 100, 400, 500, etc. etc. yards or meters any stroke, bike ride, or run and it gives you your work out. It tells how fast you should train and how to do - Max V02 or anerobic training.

He sold these programs for $295 to several coaches.

I am starting to follow the prescribed work outs and will let you know what I find out.

If you are age 33

Your Resting HR is 50

Aerobic minimum HR 132.2
Anaerobic threshold min HR 159.6
Anaerobic threshold max HR 173.2
Max V02 min HR 173.2
Max V02 max HR 180.15
Lac tolerance HR 182.52

If you do 5 x 25 on 15 sec rest 30 sec then do 7 more sets at Max VO2 along with your regular warm up of 1000m and 1000m warm down you will have a very nice little work out.

When I do this workout I swim my 25 in 15 sec rest 15 sec x 5 rest 30 sec and repeat this 7 times. A female swimmer to get the same effect as a male should do 10 of these sets.

You can also do 5 x 50, 5 x 75 same number of repeats. Do not do max V20 workouts more than twice a week