How fast does muscle strength decrease?

It doesn't really decrease along as you eat alot. you don't exactly have to work out to keep your muscle up if your happy with the size just do like 2 hours a week and make sure you EAT or it WILL decrease. I do Martial Arts not boxing or anything so i don't want to have huge biceps I'm happy with the size they are now and all i do to maintain them is eat and go on on the kickbag a few hours a week.