i am an athele too ..n that best way to improve your time ..is just as swanso5 said...improve your start ...build more power in your legs. doing explosive stuff...such as jump...go down do a push up..n then jump as high as u can..keep doing this..with time your gonne developpe endurance n explosiven...

well it depends ..if your trying to get cut or burn the extra fat well runs after cuz u ill burn more like that cuz the body s gonna be tired ...but you could do them on separt day too so that u can go all out in each giving the 100% of your cencentration, time, energie... it all depents on your goa...