As a long time track and cross country coach I have heard many excuses. I am making a list. I will start with a few. Add to it. Thanks!
Too cold
Too hot
Too wet
Too windy
New shoes
Old shoes
Stolen shoes
Shins hurt
Knee problems
Forgot my running clothes
Headache
Backache
Dehydrated
Over-hydrated
Competition too tough
Competition too weak
Ham string pull
Achilles problem
Broken toe
Track too hard
Track is too soft
Track was too long (can you believe this one?)
And finally,
I have to get my sister off the bus
I have to go watch my girlfriend play soccer!