Yup, but there's also the reverse factor that those who are approaching death rarely are capable of walking that far. I strongly suspect that most measurements

Yup, but there's also the reverse factor that those who are approaching death rarely are capable of walking that far. I strongly suspect that most measurements of factors related to longevity are actually measures of health. That being said, I think both strength and cardiovascular fitness matter. If nothing else, strength matters in terms of being able to save yourself from a stumble.