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.
Errors in side sleeping occur when one leg overlaps the other. This causes an imbalance in the hips that can lead to tightness and pain in the hip flexors, IT band, low back and knees. Another common error is sleeping with hands under or over the head and scrunching the pillow so your head is elevated. Symptoms from this error in your sleeping position can include.