How to relieve thinness in arms?

Use weights. Depending on your age and strength, use weights to do arm exercises--certain exercises build up your biceps and others your triceps. Start with 10 lb weights if you have never done it before and do 15 repetitions. Use internet to look up how. Also good nutrition, make sure you take in a balanced diet of whole grain, fruits, vegetables, and lean protein which will help build healthy muscle.
Increase muscle. Size. Hese exercises help to build arm muscle: push downs, pin presses, dumbbell wrist curls, dips, rolling extensions, barbell wrist curls, preacher curls, chin ups, lying barbell triceps extensions, thick grip curls, concentration curls ; lying dumbbell triceps extensions.