I don't gym, I work in an office and have a very sedentary lifestyle. Yet, I've been blessed withquite big arm muscles. Definitely not "go to the gym 5 times per week, eating 200 grams of protein each day"-muscles, but still muscles.

I am also strong and can easily keep up with my police and military friends who go to the gym several times per week eo excersise.

Then I have other friends, with the same lifestyle, who are basically sticks.

What causes this? I always thought muscles and strength was determined by how much physical activity you do and if you eat right, but I am the anti-thesis to that and still have good strength and muscles.