Question: How can I minimize the time spent working out?

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I've been walking quite a bit lately but it's getting so monotomous and takes 60 minutes. I'm not much for jogging because it hurts my knees. I do low impact workouts a few times a week but see that I am burning about the same calories there. How can I get the most out of my workout? I don't have a gym membership, I do have two pound weights. I'm not interested in the shred or insanity workouts. Is there any way I can make better use of my exercise time? Can someone give me examples of their own workouts that they have been able to stick to? I am 41 with 3 little kids and I need to work around that. Can anyone suggest a good youtube workout video that is about 30 minutes? I'm desperate for something new. Thanks in advance. I won't be able to read thread til tomorrow.