These test results are only findings or data that can be used in conjunction with other findings to make a diagnosis and corresponding treatment plan, but are by themselves, insufficient for a definitive answer.
When nerve conduction is impaired, one expects a nerve disease -- generally some sort of demyelination of the large (and fast) A fiber type nerves, which are motor nerves.
Causes for loss of the myelin can be mechanical, for instance, from foraminal stenosis of spine disease, or due to disease, for instance, as in MS (multiple sclerosis).
Please keep in mind that I am providing information only, and am in no way suggesting that you have MS.
Proper diagnosis of this disease requires more testing -- a family history, a physical examination including a complete neurological exam, and other diagnostic tests.
Please ask your doctor for accurate information specific to your signs and symptoms.