Good question....
Basically for the person who doesnt do any form of exercise, then any form of exercise is good, be it 10 minutes or 30 minutes. However, as you rightly pointed out some of us are used to exercise, then how much is enough? The answer if you believe all the latest studies is this. 1 hour per day of exercise. The old thinking was 30 minutes 5 times a week, but it has been found that this is not enough exercise to boost the metabolism or aid weight loss. For Women it has been found that a minimum of an hour is needed to boost the metabolism and to aid in the weight loss.
That being said I have posted on these threads before about training, what music to listen too and which exercises to do. I especially like the question about cardio or tonning and I will answer that bit quickly here.
TONNING.... with some cardio. It is a misconception that doing tonning exercises or free weights will turn you into Arnie! It wont, well not unless you are going to do it for years and eat a specialised diet. Tonning increses the lean muscle mass in the body, meaning you will burn more calories, and over a longer period of time. Cardio is a quick burst and has no sustained weight loss implications, except for the fact that you will burn 800 or so calories in an hour.
So, do both but a large proportion of your exercise should be resistance/free weights/tonning with a small section being cardio.
Read more on this forum:
www.clubdietplate.com/index.php/forum.ht...;catid=13&id=385