Optimum meaning the best out of a number of possible options or outcomes, In this case for best frequency (number of days per week) to workout for best results...
Everyones workout schedule is different so there is no set programme or frequency which could be applied to everyone.
It all depends on frequency(how often) intensity (difficulty level) time (how long) type (of activity eg weightlifting, running, body pump etc) (FITT)
OK taking the above into account some people are in the gym at least 5 times a week, while others go once or twice a week....
WHY? When you do a light workout it hardly takes anything out of you, your recovery is fast.....demands on your bodys organs (liver kidneys pancreas etc) is low....on the other hand after a tough gruelling workout your organs need time to recover and muscles need rest to grow.
More info on training coming soon!