Age 45, male, caucasian, 5'8, 164lbs. i hike 40 - 50 miles a week. my blood creatinine is 1.1mg/dl. could this be due to the increased leg muscle?

This is normal: You're right and should be commended for your athletic activities. I'm really sorry for the silly fad that some labs are undertaking, using a reference range for creatinine levels based on people who don't exercise. When i was lifting weights every day, my creatinine ran 1.6-1.7. Today, every fitness buff is an instant "kidney patient" and both pathologists and nephrologists are tired of it.