The cause is frequently unknown. Hypertrophic cardiomyopathy is often and dilated cardiomyopathy in a third of cases, is inherited from a person's parents. Dilated cardiomyopathy may also result from alcohol, heavy metals, coronary heart disease, cocaine use, and viral infections.
Consider the number of reps. You can also confuse your muscles by increasing or decreasing the number of repetitions you do during any given exercise. For example, if you normally do 12 repetitions, do 15 or 18 repetitions, but with a lower weight than you would normally use.
Although you might think scientists figured out a long time ago why muscles get tired, you would be mistaken. Until recently, there was no straightforward explanation for why your arms and legs feel like limp noodles after vigorous exercise like lifting weights, doing aerobics or climbing a flight of stairs.