Currently, assessing the severity and progression of symptoms in a subject diagnosed with muscle dysfunction, in particular SMA, involves clinical monitoring and testing of the subject every 6 to 12 months. However, more frequent monitoring and testing of the subject is preferred, but increasing the frequency of clinical monitoring and testing may be expensive and not very convenient for the subject. Thus, as described herein, the severity and progression of symptoms are assessed via remote monitoring and testing of the subject outside the clinical environment, providing advantages in terms of cost, ease of monitoring, and convenience for the subject. Systems, methods, and devices according to the present disclosure provide a diagnostic for assessing distal hypomyotonia in a subject suffering from muscle dysfunction, particularly SMA, based on active testing of the subject.