running up/down stairs exercise?

Main muscles used would be the quadriceps, hamstrings, gastronemius, and glutes. You can go down stairs backwards (use the rail); it is easier on the knees. You can do 1 leg squats for 1 step and then increase it to 2 steps etc.

yes that is great excersice, make sure you stretch first though and make sure not to trip. running up and down stairs is good for weight loss as is skipping on a skipping rope. double jump skipping rope is best and both these exercises will rapidly get your legs into shape so fast it may scare you. another even better way is swimming. to start off (if your not too fit) try walking in water up and down the pool and then progress to laps. you can never ever be too fit for swimming, it makes you lose weight really quickly and gets you into shape. also with dieting try eating every 3-4 hours in small healthy proportions instead of 3 big meals a day because beleive it or not it keeps your metabolism going which burns fat. also try to cut out as many soft drinks and junk foods as possible and water it the healthiest thing you can drink. hope this helps.