there are some researchers that support that theory, but in my experience it isn't the case.

Yes,we have met some individual that were incredibly strong. There's a girl that we know her nephew is 8 years old,mentally challenged & he can lift a full size couch to retrieve items from underneath

This has been demonstrated for the senses. Deaf people have stronger acuity in their other senses, as if the body compensated for it's handicap. The same is for blind people, etc. Blind people tend to have excellent hearing.

Yes it is true but not only in strength. People with autism are mentally challenged, although most people with pervasive developmental disorder or PDD have normal or even above-average intelligence. In contrast to being mentally challenged, which is characterized by relatively even skill development, people with autism show uneven skill development. Those with autism may have problems in certain areas, especially the ability to communicate and relate to others. But they may have unusually developed skills in other areas, such as drawing, creating music, solving math problems, or memorizing facts. For this reason, they may test higher perhaps even in the average or above-average range on nonverbal intelligence tests. Best regards.

I don't know WHY it is, but it is true that a lot of mentally challenged, or in my own experience the mentally retarded, people are incredibly strong. Some theories suggest that it is because their pain receptors are not all firing, due to their brains being wired a little differently than the average person. So they are able to do more physically to improve their strength, because of that. Like when I lift something heavy very many times, I get sore and stop. They don't get that pain reaction, so they continue. Makes it difficult when you work in a jail, because we do have people that are mentally impaired that are arrested and brought to us. Due to the mental challenges, they are not always as able to control emotions, get angry or scared and start fighting us. Unfortunately, we have to restrain them in order to protect them from hurting themselves or others. This is easier said than done. We try to use pressure points and joint locks to induce pain and gain compliance without doing any physical damage, but a mentally retarded person just doesn't usually feel that pain and keeps on swinging. It usually comes down to having to get many officers and use brute strength to restrain the individual. And it is hard on us, too, because we know it is not that persons fault. But as I said, we have to keep them from hurting themselves or others until their legal situation is sorted out.