Your heart! It's your most important muscle by far, and the most neglected. Distance running is great for your heart! Heart disease is the #1 killer in the U.S. right now. However, I would not classify running in general as a muscle "builder" (even for the heart). Distance running is a low intensity aerobic exercise by definition, and as such does not stimulate hypertrophy (muscle building) to any great extent. You will however gain endurance in your legs, lower back, butt, calves, and even shoulder and neck!
Mostly your Quad muscles
you can build your abb muscles by doing sit ups and abb workouts also you can flex your abbs while you run or walk
Your triceps and biceps. Your calfs and thigh muscles. there, i think, are muscles in your tourso that are active. then your heart and lungs.
Absolutely. As you keep running more and more your endurance increases and you get more fit. If you get tired after running just a km, then your muscles are not yet ready for running. You need to build them slowly.
You do excersise to build muscle. Ballet, cycling, walking and running are great for this. You can also rise on to your tippy-toes and stay there for a while to help develop those leg muscles.
Quite a few muscles go to work while running. While there are the obvious muscles (Such as calf, thigh, hip, and hamstrings) other muscles are subtly at work also. The abdominal muscles are slightly worked, along with the arms and back muscles. The arms are constantly swinging, going against air friction/wind during the run. Your back helps keep you in the upright position and is constantly shifting while you take each step. So pretty much your entire body goes to work while running (even your toes which push you off the ground). Hope that helped :)
Pain in the stomach while running is called a side stitch. This may be due to membranes and muscles rubbing against each other.
Crunches build muscles while situps build abdominal muscles. Each workout is important based on individual needs.
This is just a regular cramp from running, run more, build up your endurance and all should be alright.
Running up stairs will build the quads, upper front of the legs and the calves from the pushing while running up on the toes. Over all tone will be the results. Adding the return of going down the stairs will balance the musle groups. going up will equal doing lunges.
The best way to build your stamina is to use it. The same is true for your muscles and your brain. You should begin a training regimen involving a lot of running. Many professionals recommend uphill running, wind sprints, and long-distance jogging. You cannot get quite the same benefits from a treadmill or stair climber type of machine; Most of your body weight stays stationary, and so your legs do less work. If you are carrying excess body fat, you my want to consider reducing that. Having to move less wait while running will automatically improve your stamina, because it will take less energy. If you smoke or take recreational drugs (including marijuana), they will reduce your stamina. Eliminate them. Build your leg muscles. While it is true that adding muscle weight will make it harder to run, stronger legs will counter-act this effect and then some.
After a while it helps your finger and hand muscles. It can also build forearm muscle after extensive playing on higher levels and harder songs.