If you’re extremely fatigued after a mild workout, it just might be that your CMT is to blame rather than your exercise routine. Published in Nature Advance, the study identifies a faulty signaling pathway that appears to cause exercise-induced fatigue in mouse models of muscular dystrophy. Strangely enough, the study shows that the erectile dysfunction drug, Viagra, can overcome the signaling defect and relieve the fatigue by increasing blood flow to the muscles.