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Steven F. Viegas, MD, Galveston, TX
Hand and upper extremity overuse and repetitive injuries in astronauts have been and continue to be a common problem in the space program. The demands on upper extremity use in the astronaut training program, the zero gravity environment of space, extremes of the conditions in space, the effects of space travel on human physiology/anatomy and the constraints and pressures of space suits and gloves can all negatively impact on upper extremity function in ways that can result in overuse/repetitive injuries.
Even prior to space flight, high demands on the hand and upper extremity are seen during under water training in the Neutral Buoyancy Laboratory (NBL). Traumatic onycholysis, hand pain and neuropathies can develop as a result of the six-hour training sessions. Shoulder problems can also occur, particularly during inverted (head down) activities, which although a good simulation in the NBL, the earthbound training cannot eliminate gravity and therefore results in restricted scapulo-thoracic motion and concentrated loads at the shoulder.
Muscle atrophy and bone demineralization is a well-documented and recognized concern for humans who remain in microgravity environments for extended periods of time. The upper extremities, however, have not typically shown the muscle atrophy and mineral loss which have been observed in the back and lower extremities. In fact many of the astronauts detail symptoms that are consistent with significant, and even overuse of the hand and upper extremity musculature. The hand and upper extremity is used to stabilize, accelerate, decelerate, interact with the environment and to counteract any action that would displace and/or malposition an individual in zero gravity. During extravehicular activities (EVA's) and/or during extraterrestrial lunar and/or possible future planetary (martian) exploration, the hand/upper extremity is still involved in all of these activities while additionally working against the 4.3 atmospheres of pressure in the space suit and the resistance of the gloves.
In zero gravity, spinal elongation of one to two inches can occur with resulting tethering of nerves and/or brachial plexoraphy. Fingertip trauma and infections along with other upper extremity problems are a concern, and their treatment may be a greater challenge with the limited supplies, facilities and capabilities in the environment of space.
Future plans for space exploration include continued servicing of the Hubble telescope, construction and maintenance of the International Space Station, contingency EVA's for shuttle tile inspection/repair and hopefully further lunar and future Mars exploration. With any and all of these endeavors there will be continued and even greater demands on the hand and upper extremity.
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