67-Year-Old Steve Martin — SHAPING UP for My Newborn Baby

Hoping to stay alive long enough to see his newborn kid graduate elementary school, 67-year-old Steve Martin worked on his fitness by hitting the road on his workout bike this week.

Martin”s rep just confirmed that the actor”s 41-year-old wife Anne Stringfield gave birth to their first child back in December … but the couple hasn”t revealed the sex or name of the child.

Whether it”s a son or daughter, he”s now working out for two.