Bulking up is not the way to go when it comes to lowering race time! Protein and carbs the night before a race, and a vigorous stretching warm-up before the race to limber up the leg muscles. If you're talking foot races, stationary bikes set at high tension are an excellent way to streamline thigh and calf muscles.

yes they will it works with me

The 800m is a prolonged sprint, so some bulk helps.... I wieghed 170 lbs in a race where some of the top competitors were wieghing in at about 140 and I was still successful... the most important part of your question was about the crunches... anything that strengthens your core will be beneficial to your run time... the best thing that you will gain from pushups is the fast twitch muscle fibers required to explode from race pace to your kick with three hundred meters left to go... be sure that if you incorporate pushup...

The 800m is a prolonged sprint, so some bulk helps.... I wieghed 170 lbs in a race where some of the top competitors were wieghing in at about 140 and I was still successful... the most important part of your question was about the crunches... anything that strengthens your core will be beneficial to your run time... the best thing that you will gain from pushups is the fast twitch muscle fibers required to explode from race pace to your kick with three hundred meters left to go... be sure that if you incorporate pushups you perform adequate stretching regimens afterwards to prevent you from tightening up for muscles during a race....