A type of weakness that occurs after a muscle group is used and lessens if the muscle group has some rest. That is, there is diminution of strength with repetitive muscle actions. The phenotype is Fatigable weakness (HP_0003473). Also known as: Fatigable weakness of limb muscles, Generalised muscle weakness due to defect at the neuromuscular junction, Generalized muscle weakness due to defect at the neuromuscular junction, Myasthenia, Myasthenic weakness, Proximal muscle weakness due to defect at the neuromuscular junction.