How these muscluar contractions work?

How do they work, and what exactly do they do?

Is there any work outs, types of runs, or sports that can boost my staminaa,

does that ab belt achully work? you know that contoar belt?

Should I work out more or am I fine(normal)?

is running up and down stairs a good work out? if so, how many should I do a day?

I received an email about the Kangen Water and it sounds to good to be true, i just want to know if its a scam or is it leg...

what are the major superficial muscle groups? what do they do? how do they work?

Remember those machines where a belt wrapped behind you and made your fat shake while you stood there. how were those suppos...

What are good work out videos for yoga, pilates, aerobics, etc.? Is there a specific trainer and or brand that's good?

I am 13. can working out stunt my growth?