I'm with R41 -- 40 was the beginning of being middle-aged.. But my 50's have shown me it really is the beginning of the end. I had an sports injury @ 50 that made it difficult for me to exercise, and I put on 20 lbs. The knee surgery I had to try to correct it only left things worse.
According to the National Institute of Neurological Disorders and Stroke (NINDS), the sudden, involuntary jerking of a muscle or group of muscles while drifting off to sleep is called myoclonus. It is caused by sudden muscle contractions, also known as positive myoclonus, or muscle relaxation, which is referred to as negative myoclonus.
Frequent Muscle Twitches and Pulled Muscles in Upper Back. I frequently pull the muscles in my upper back while sleeping with even very normal, slight movements such as adjusting the covers, slowly repositioning myself, moving my arm, etc. Does anyone know why this might be? I would have thought that my muscles were warm and relaxed while I was sleeping and not prone to pulls.