While I was leaving the pharmacy today, I was behind a little, old, white-haired lady. She stopped and told me I should go around her, saying “I’m pretty slow.” I started to say “that’s alright, I’m catching up to you,” my intent being to convey that as I get older, I’m also getting slower and that her pace didn’t bother me.
As a currently “mobile but getting less so all the time” middle aged guy speaking to a “less mobile” senior citizen and trying to convey that I am aware that age stalks us all, would not the correct phrase have been “I’m catching down to you?”