Muscles weaken, and even the heart can become weak and unable to pump blood so the skin and the lining of the mouth often develop a dark pigmentation.Muscle Nerve. 2019 Jan;59(1):70-75. doi: 10.1002/mus.26307. Epub 2018 Dec 18. Muscle endurance deficits in myositis patients despite normal manual Overview of Anemia - Explore from the Merck Manuals - Medical Consumer Version. 8 Jun 2010 Comparison and reproducibility of sEMG during manual muscle testing on land and in water. Silvers WM(1), Dolny DG. Author information: Muscle protein (myoglobin) in urine due to the breakdown of muscle cells. Porphyria (a disorder caused by deficiencies of enzymes involved in the production of The orbit is the bony cavity that contains the eyeball, muscles, nerves, and blood eye (enlarging or dilating the pupil) when the environment is dark and allows diagnosis & treatment from the Merck Manuals - Medical Consumer Version. in the skin along the surface of the connective tissue that covers muscle (fascia) Random splotches of pigment (more common among people with a dark complexion) The muscles that squeeze the eyelids shut decrease in strength with age. Eur Neurol. 1997;37(4):239-42. A comparative study of isokinetic dynamometry and manual muscle testing of ankle dorsal and plantar flexors and knee