On this forum, Flyinfree, Sparrow, BikeSwimLaugh, Drex, and I (up until a recent medical issue came to light) are all heavy cardio folks but we all incorporate weight training as well.
OMG...I am honestly so flattered to have been sited & included in this group!!! Thanks!
Also, everything Wrangel wrote is uber-valid....really read & re-read that info!
In my opinion, we are each given different talents & abilities in life...seems like you've stumbled onto something you do very well. For me, I take 2 spinning-classes back-to-back and then swim a mile or two....about 3 hours & 2k calories. I think nothing of it, others think I'm crazy. I can bike and swim....but running has never been my thing. I'm looking into it pending my knee-injury recovery. Anways, back to you....
The following is what I've been taught, told and understand.....I'm not stating this as The Law, but as something to think about and consider:
I've been taught again and again that weight-training is something that is very demanding on your body and you want to come into it fully fueled with lots of energy at the ready. My understanding is that weight-training is so intense that much of it is done anaerobically and consumes a great deal of creatine-phosphate/ATP & glycogen. For that reason, you want to do it first in your routine and make use of all that primo at-ready energy to get the most out of your workout.
I've also been told that weight-training should not exceed more then 1 hour because after an hour your energy is diminished and this is where catabolism starts to come into play. So; weights first, cardio after. You mention you do running and then weights...you may wanna reconsider this sequence.
You ask "how much cardio is too much"? Well...the thing I've found is that your body is very adaptive to the demand you place upon it. My first mountain bike rides were about 14 miles and they were done in my lowest gears with me huffing & puffing and on the verge of taking rest. Today I can crank-out 24 miles rides on much steeper hills and I'm in higher gears moving faster. Same thing with swimming...the first time I did a mile it was crazy, my record now is 4-miles. If you wanna talk crazy-long, FF is the king....this guy is capable of like 100-mile bike rides and runs 26 miles!
Point is, your body will adapt. Science tells us that maximum health benefits derived from cardio are reached at one hour...anything more is fat-burning. Is this accurate? Who knows, science is constantly revising it's position.
What I have found, recently (wth my injury) is that your body has a very keen sense of how much is going out and how much is coming in. If you are in deficit, you'll be hungry and your body will attempt to reconsile the situation in a survival-like manner. With my injury I lost my racquetball, spinning & biking...which accounted for about 4,800 calories per week. In all, I just ended-up eating about 700 calories less per day and everything stayed at equillibrium. 700 calories doesn't sound like much, but we often forget how packed with calories food is and after a solid workout we feel pretty entitled to eat a bit and replace what we've burned.
The other thing is, your body will also adapt to the demand and become more efficient. I noticed my bike rides were requiring less and less calories.....which is why I extended them.
I say, if you enjoy the cardio, then do it....but from a practical perspective, I think an hour a day is probably good enough. If you want to do more, you can....but to reap the turbo-charged kick-ass benefits of accelerating your weight-loss, you'll have to really focus on how many calories go in. Or as Wrangell might point out, you can burn an extra 800 calories, but if you replace them, it's a wash.
Suggestions:
Mix it up....
Try some swimming, it's great upper-body cardio and can really build your chest, arms & back! Woman often mention how much they love a swimmers body!
Biking is also great...it's much lower impact on your joints and uses different muscles in your legs. Since you're in a gym, you may wanna check-out a spinning class. Like me, most people are very skeptical of how much fun it can be working on a stationary bike...but with the right music, instuctor and lycra-clad hotties.....it's an addictive blast!!!!!
And most of all...enjoy what you do for the health benefits. I'm sure you're bloodwork looks great, you're feeling good about yourself and nothing...NOTHING beats that natural endorphin feeling you get after getting in a good workout!
Oh...and on a last note (just to stay consistend with my novel-length replies)....this may sound like another one of my sex-related jokes...but seriously, at least for me and others I've talked to:
If you feel horny and are looking at woman like they're meat....everything is fine. BUT....if you're overdoing it on the cardio and pushing yourself too much (excessive), you may notice your sex-drive will diminish sharply. Don't ask me why, but I've found this consistent with other people. It's probably because the body is stressed or you're watchign too much Oprah!
