The parts of the body affected by early symptoms of ALS depend on which muscles in the body are affected first. About 75% of people have limb onset ALS. In some of these cases, symptoms first affect one of the legs, and patients have awkwardness when walking or running or they notice that they are tripping or stumbling more often. Other limb onset patients first see the effects of the disease on a hand or arm as they have a difficult time with simple tasks requiring hand dexterity, or ability to move small things, such as buttoning a shirt, writing, or turning a key in a lock.