but I really have to ask it! Why does running not make you more muscular??? I know that cardio burns muscle... but why? I thought what builds muscle is using the muscle... and I know when I am running, all my mucles are into it. The reason I am asking is because I adore cardio... and I really hate resistence training. I know I need the resistence training to build muscle... but I don't really understand how running will leave me all flabby as I lose weight. I would think it would make me lean and lovely, like most of the other runners I know. Just looking for some insight... thanks in advance!!!

and when I say lean, I mean you see the lovely muscle definition in their arms and legs, and they are quite thin. Do runners generally still do a lot of resistence training, and that's why they look that way?

First of all, cardio doesn't "burn muscle".

Running is a good fat burning activity, since it burns a lot of calories. People who run, if they have good muscle tone underneath, will look quite thin and muscular because running has burned off their extra fat, exposing the muscle underneath. Running can also do some mild toning on some of the leg muscles, most notably the quads, but doesn't do any serious sculpting like you would with strength training.

Muscle definition in arms is never going to come from running, except in that, when you burn off fat, it exposes muscle you already have in your arms since the fat layer isn't covering it up. Those muscles won't get stronger or more toned by running, but will get more exposed.

So runners = lower body fat % = existing muscle is more visible, which explains why a lot of runners you know have a muscular look. If their muscles are REALLY toned, though, not just peeking through, they are likely doing some strength training.

Amanda's right about the low body fat % allowing you to see muscle.

The reason that running, and other cardio, can't build muscle is the nature of the exercise. In a nutshell, muscle is build by stressing it with weight, which makes microscopic tears in the muscle. When the microscopic tears heal, the muscle grows back stronger. That's why bodybuilders say that muscles grow when you're resting, not when you're in the gym.

In order to stress the muscle and create the tears, you need to work it to fatigue in a period of 60 - 90 seconds, which is about as long as the average weightlifting set. In other words, your muscle needs to reach exhaustion in a very brief period of time.

Now think about running and other kinds of cardio. Obviously we aren't working our muscles to fatigue in 60 - 90 seconds, since most of us can do continuous cardio for at least 30 minutes without rest. So we're not putting muscle building stress on the muscles when we do cardio. You can build endurance with cardio (and burn a ton of calories!), but not build muscle. We have to add in weightlifting to our exercise routines for muscle building and strengthening.

I hope that makes sense! Both cardio and weights are important components of everyone's exercise programs.

The long distance runners I know do all-over resistance training for the most part when training for a race. A lot of "learn to run" programs encourage this as well. To gain muscle and improve definition you need to overload the muscles and running or any other form of cardio does not do this.

I definitely agree with what mandalinn82 said. What you're seeing in runners (if they do no resistance training) is probably a very low body fat percentage so they appear to have more muscle definition.

Why don't you like resistance training? I love running too and I find that mixing things up and lifting weights only progresses me further in that. Running is killer but if you do it everyday your body WILL get used to it and eventually you won't be getting the same benefits you were before.

I'm going to guess that I learned about putting your mind in your muscle (thinking hard about exactly what you are doing to get that dumbell raised) here on 3FC.
When you're comfortable, the right music, sunlight ... it's akin to meditation IMHO. It's an amazing feeling to listen to your body do something wonderful that it was designed to do.

I resisted resistance training (had to say it) for a long while because I found lifting weights boring. Then I realized my fitness center had several different classes using weights and I tried them. In a group setting I liked it, I worked harder, and there was a lot of variety in the activities we did, so I did not get bored. Now people compliment me on my shoulder and arm muscles. Who knew there were any in there? I am also very happy I started doing this since I have to consider osteoporosis issues. So maybe you might like a class involving reisitance work of some kind?

Wouldn't you have to run pretty hard and long, with no snacks, in order for cardio to resort to burning muscle stores (glycogen stores?) for fuel? I've been trying to understand this, as well, but still feel confused by the idea. Doesn't running just work a different type of muscle fiber (ie, not the type that can be bulked up with resistance training)?

Thanks everybody! Pink, I had never thought about doing a class. Maybe I should try something like that. I just can't bring myself to do weight training for any real period of time. After 10 minutes I am bored out of my mind, lol. I still try to do it a couple times a week, but it's hard to push myself to get off the treadmill or eliptical and go and do the machines or weights. I like how cardio makes me sweat and makes my legs burn and gets me all out of breath. I like feeling exhausted after my workout. When I do resistence training, I just don't feel like I am really accomplishing anything. I mean, my muscles get really tired... but it doesn't feel like a "good" tired, like what I feel with cardio. Are there ways that I can build muscle without getting on the machines or lifting weights? Could I successfully do it with pushups, crunches and leg lifts? Those, for whatever reason, feel a lot more... entertaining, lol.

Yes! Body weight exercises, with additional hand weights if you want them later, are great (and, from my current knowledge of how the body works, will actually work better for building muscle). Squats, lunges, pushups, tricep dips, etc. all get your heartrate up while building muscles, so you may get more of the tired feeling you're looking for.

I circuit train because I get bored easily...lol (it's also why I vary my cardio as much as possible). I do pushups, squats, lunges, ab exercises, with bursts of jumping rope, jumping jacks, mountain climbers...stuff like that. So I'll go like...pushups, then squats immediately afterwards, then jump rope for one minute. DEFINITELY not boring. I rarely use the machine and putting it in a circuit of exercises also makes that more bearable. The other thing about throwing in those cardio intervals is you get your heart rate up so it feels like a "better" workout.

So yes! Do body weight exercises! They're great and force you to control your movements instead of having a machine do it for you. Second...I think a class is a fantastic idea. There are ones that do "boot camp" at my gym which is mostly body weight and dumbbells as well as circuit classes. Third, try mixing it up as much as possible. Once you get the hang of it...maybe you'll start to enjoy it...

I think the circuit training idea is key for me in why I actually get any resistance work done. I really like my weights classes at the gym because they mix up hand weights and body weight work with a bit of cardio, and we never stop moving no matter what - we do lunges, then biceps, then squats, then triceps, a little cardio with the step to get our heart rates up, etc. etc. etc. I do come away from this class with the good kind of tired feeling - I know just what you mean - I burned some calories, I did strength exercises, the whole thing. Plus, there's no chance for me to think about what to do or whether to do it- the class just keeps rolling along and I go with it. Actually it's relaxing! (I know...) And it has helped me to have an instructor pointing out the correct way to do the work so as to get the most benefit and prevent injury. So if I sound like a commercial for classes, I am a believer, since I am sure I would not do this kind of thing on my own. (In fact I didn't. I'm still shocked that I actually like doing weights now after all that time really disliking it.) Makes me wonder what will happen next??? Life's full of possibilities!

This is a long and complex question and probably should have its own thread but...

Glycogen is the way that carbohydrates are stored in the muscles for later use. Burning glycogen does not burn muscle.

When you are at rest your body primarily burns stored fat for fuel. As your heart rate increases, the body starts to burn stored carbohydrates for fuel. The higher the heart rate the greater the percentage of carbohydrates to fat that is burned.

When running, the glycogen is released from the muscles, and burned as the primary source of fuel. When you stop running and eat and rest, the carbohydrates are restored in the muscles. The muscle is not damaged by this process.

The key point is what you mentioned....if you run a long time, HARD without fuel. Most people have enough glycogen stored in their muscles to support 60-120 minutes of aerobic activity depending on training and intensity. Long slow miles increase the muscles ability to store and use glycogen as fuel. They also train the body to use fat more efficiently as fuel so that at the same effort the ratio of fat burn to carb is higher.

The body will only burn protein for fuel under duress as a very last resort. It is usually only seen in people who run extremely long miles at extremely high effort repeatedly or who do not fuel properly or who have electrolytes out of whack - those who have entered overtraining syndrome.

Running can build muscle mass in specific cases. Sprinting builds muscle mass as does hill work. However, the stress put on the connective tissue during these kinds of workouts is too high to be done frequently. People who try to push with these type of workouts without a proper base end up injured. Weight lifting in general is easier on the body and more productive if muscle mass is the goal.

I have to say my legs have actually built some muscle from cardio, although I do really push myself when I'm doing it. For instance rather than spinning my legs rapidly with little resistance on a bike, I keep the resistance high as I can manage to maintain for more than a few minutes so each push of the pedal takes real effort. I'm not sure if that can be considered muscle building exercise or not? My calves bulge out noticeably when I flex my leg muscles, which they did not before so I assume it did some good. I hate lifting weights too, I do make myself do it here and there but I focus on the cardio as well, its a lot more fun for me. I wish there were classes where I work out like others have mentioned, I bet that would be a way for me to get it in without it feeling like a chore.