How much exercise is too much.. What is your WO Schedule.

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I have been doing Zumba (1 hour), abs class (15 minutes) and an WOD class (1/2 hour) 3 days a week in the morning. Then I do Zumba at night 2 to 3 days a week and I also started C25K. I lost my weight doing this now I am at a plateau. I would like to incorporate a weight training schedule ... I need to lose 40 Pounds, I am 5'5" and about 191 pounds and I am 51 years old. I am not sure if I can do Zumba the same day as working my legs and all that other complicated stuff for a newbee... I read on here Cardio hurts your weight lifting days. Should I do a whole body circuit or break it down to only certain body parts different days. HELP where do I start...