I'm training for a marathon and I've recently noticed that when I run
more than 8 miles at once I have a hard time walking up stairs. My knees
do not hurt, but they just give out. Any suggestions???
Curious - do you cross train? Do you wear orthotics? Do you stretch before you run? Are your shoes in good repair? Do you have an old cartilage injury? Just too many issues to resolve your question into a likely source of your problem...Perhaps you should consider all of the above.