Magnesium and potassium, along with sodium and calcium, are examples of electrolytes that are present in the blood. Electrolytes help trigger and regulate electrical impulses in the heart and low levels of magnesium and potassium can lead to an electrolyte imbalance, which can contribute to arrhythmia.
Passing hard stools is usually as a result of constipation or the infrequent movement of the bowels. Most healthy people have at least three bowel movements per week, according to MedlinePlus. If you are unable to have a bowel movement or are having difficulty passing stool, contact your doctor.
So it makes sense that the most common reason of hard stools is irregularity of bowel movements causing constipation. To a smaller point, hard stools may be produced by insufficient fluid intake, as the colon is required to draw excess water from the stool.