Muscle memory doesn't apply to cardio as much as weight training and even then, it refers to the muscles ability to regain strength/muscle quickly after taking a long break from training. Not in the context you are using it.
As you become more fit and lose weight, your cardio will become easier to perform (less resistance, you'll have built more strength and endurance). This has less to do with the 'type' as much as the intensity you will have to perform at to create the same calorie burn that you once did. However, changing the type of cardio you perform may increase the intensity because you are using muscles that are less developed than the muscles used in the type of cardio your body has adapted to.
As long as your heart rate is in your target cardio zone, your cardio is efficient enough to burn calories. If you notice your heart rate is not getting as high as it once was (you are becoming more fit) at a certain speed, go faster or do intervals. It is natural however, that as you lose weight you will burn less calories through activity and exercise, you'll have less resistance (in the form of weight).
As far as weight training goes, as long as you continue to increase weight/resistance... you will continue to challenge your muscles enough to build strength/muscle (or simply maintain if that's your goal). It will just come down to whether or not you're feeding them enough but generally for a beginner (first year or two even) as long as you are increasing weight you won't have to worry much about stalling out due to nutrition unless you are on an extreme calorie deficit or on a low protein diet.
Edited by: JENNILACEY at: 9/16/2013 (11:27)
Take your focus off the Marshmallow. www.leangains.com/2010/01/marshmallo
"Toning" is marketing muscles to women who are afraid if they pick up a barbell, they'll leave the gym looking like She-Hulk. It doesn't happen, what does happen is you get results. Lifting Barbie weights does nothing but waste time.
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