Physioloigy lesson here:
Unless you are compensating with large amounts of clean food, it is impossible not to burn muscle doing cardio session of over 30 minutes. That's just how the biology works. Since staring to lift INTENSELY 2 years ago, the only times I have experienced muscle (and strength ) loss, has been doing Camp Pam Brown, which adds a lot of cardio, and training for the 1/2 marathon. I was lifting with max intensity during both those periods, but steadily losing muscle due to the horrific cardio loads.
When actually doing cardio, you burn no fat- once the glucose and glycogen stored in your liver are depleted, your body turns to muscle for it's fuel. That is why BFL is based on a 20 minute cardio session: during those 20 minutes, you are using glucose and glycogen for energy- it's called a glycolitic process- beyond that, it is a "catabolic" process (muscle burning). After long aerobic exercise, your muscles will eventually repair themselves if they have sufficient amino acid pools (food and stored fat) from which to pull nutrients.
Overweight beginning weighlifters can get away with excess cardio, tho it's not going to help you, unless it just plain makes you feel better. For about the first 4-5 months you have a golden window for developing muscle, despite too much cardio. However, your muscle gains would be greater if you keep your cardio in the less than 1/2 hour range. This only applies to intense cardio- HIIT or all-out sessions. Taking a walk- even a 5-7 km one or a bike ride, is healthy entertainment.
As your body fat get lower, unless you are doing real exact nutritional analysis and eating buckets of the right foods (like Robb or Rich at L&S), you'll finding it increasingly difficult to build muscle mass or even maintain it if you do excess cardio. Also, metabolisms adjust to a level of exertion, and the more cardio you do, the more you need to add to maintain or lose.
There is one other aspect to consider, tho. That's what do you want to look like? Not everyone (in fact a lot of my friends have pronounced her comp pictures "disgusting") don't want to look like Pam Brown. Given that the long, lean look is genetically impossible for me, I'm going for the muscular.
Well enough of that. This is all based on clinical studies which I can point you to if anyone is interested, and my own recent experience.
Adriana- I sure hope nobody blows up, too! I read the paper each morning with new trepidation now that I have a new friend in Israel. My cousins returned to the US about a year ago, so I no longer had such a personal connection.
Ledom- I second the motion that your workouts look real good! Have fun.
Karen- Sounds like you had a super weekend! It's been too cold here to think of doing anything. Even getting in the car seems like being under seige.
Lana- How are you? Must be pretty cold up there too! Dh did 2 co-op terms in Ottawa when he was at university (Waterloo) and tells me stories not condusive to visiting there in the winter
OK- gotta go help with homework. I took a 6th grade take home math quiz this morning and got 1 wrong.
mel