A chemical called triclosan, commonly found in soaps, deoderants and mouthwashes and many other household products (toys, trashbags, etc), has been found to impair muscle function.
Researchs at the University of California, Davis and the University of Colorado studied its effects on heart muscle cells. By applying electrical stimulation they were able to test its effects on muscle contraction. They found that two proteins involved in contractions were impaired by triclosan.
The researches found the the chemical reduced heart function levels by 25% within 20 minutes. More research is currently being conducted.