When i was younger , i used to be such a good athlete , now when i finish i keep breathing heaps!!?

im still really fast , my bestfriend is very!!! athletic does little athletics and stuff , and she is skinny , im not exaclty skinny :S . (im 14 btw) . andd i bet her . literally i was heaps far infront , i am still a heaps fast runner the only problem is when we both finished she wasnt breathing heavily she was breathing a lil for like few seconds but thats it . but me i was breathing heaps. like is that because i am not skinny and like actually rann really fast or like ? yee im confused . i lovee running fast , i hate!!! jogging i cant do it . i just like start to runn. when i was younger i got HEAPS of 1st place medals for running . im hoping to be fit again . but i dont know how to do that. just keep running everyday? and then ill become fit. tbh when i versed my friend i hadent actually ran fast in ages. she goes little athletics every weekend and she does dance , netball and surfing . mee im not doing any activitys. does this mean im on my way to becoming fit?