Are you able to meet the physical demands of this position?

This position requires visiting several sites, some of which might be fairly remote. You might find yourself walking or hiking with field supplies up to 30 pounds, so your interviewers want to ensure that you are physically capable of completing the job.

For xample: "Maintaining good physical health is important to me, so I keep myself in shape and exercise regularly. So, yes, I am absolutely able to meet the physical demands of the position!"