Work-related   musculoskeletal   disorders   (WMSDs)   are   a   group of   painful   disorders   of   muscles,   tendons,   and   nerves.   Carpal tunnel   syndrome,   tendonitis,   thoracic   outlet   syndrome,   and tension   neck   syndrome   are   examples.   Work   activities   which are     frequent     and     repetitive,     or     activities     with     awkward postures   cause   these   disorders   which   may   be   painful   during work or at rest. Almost    all    work    requires    the    use    of    the    arms    and    hands. Therefore,   most   WMSD   affect   the   hands,   wrists,   elbows,   neck, and   shoulders.   Work   using   the   legs   can   lead   to   WMSD   of   the legs,   hips,   ankles,   and   feet.   Some   back   problems   also   result from repetitive activities. WMSDs    are    very    difficult    to    define    within    traditional disease    classifications.    These    disorders    have    received many names, such as: • Repetitive motion injuries. • Repetitive strain injuries. • Cumulative trauma disorders. • Occupational cervicobrachial disorders. • Overuse syndrome. • Regional musculoskeletal disorders. • Soft tissue disorders. Most   of   the   names   do   not   accurately   describe   the   disorders. For    example,    the    term    "repetitive    strain    injuries"    suggests that   repetition   causes   these   disorders,   but   awkward   postures also   contribute.   These   terms   are   used   synonymously,   and   in the absence of agreement, WMSD is used in this document. WMSDs    are    recognized    as    leading    causes    of    significant human   suffering,   loss   of   productivity,   and   economic   burdens on    society.    The    data    available    are    limited    and    does    not represent   the   magnitude   of   the   problem   because   there   is   a great deal of under-reporting of these types of injuries. WMSDs   arise   from   ordinary   arm   and   hand   movements   such as      bending,      straightening,      gripping,      holding,      twisting, clenching   and   reaching.   These   common   movements   are   not particularly    harmful    in    the    ordinary    activities    of    daily    life. What    makes    them    hazardous    in    work    situations    is    the continual   repetition,   often   in   a   forceful   manner,   and   most   of all,   the   speed   of   the   movements   and   the   lack   of   time   for recovery between them. WMSDs are associated with work patterns that include: • Fixed or constrained body positions. • Continual repetition of movements. • Force   concentrated   on   small   parts   of   the   body,   such   as the hand or wrist. • A   pace   of   work   that   does   not   allow   sufficient   recovery between movements. Generally,    none    of    these    factors    acts    separately    to    cause WMSD.   WMSDs   commonly   occur   as   a   result   of   a   combination and interaction among them. Heat,   cold   and   vibration   also   contribute   to   the   development of WMSD. Pain   is   the   most   common   symptom   associated   with   WMSDs. In   some   cases   there   may   be   joint   stiffness,   muscle   tightness, redness   and   swelling   of   the   affected   area.   Some   workers   may also   experience   sensations   of   "pins   and   needles,"   numbness, skin colour changes, and decreased sweating of the hands. WMSDs may progress in stages from mild to severe: • Early   stage:   Aching   and   tiredness   of   the   affected   limb occur   during   the   work   shift   but   disappear   at   night   and during      days      off      work.      No      reduction      of      work performance. • Intermediate   stage:   Aching   and   tiredness   occur   early   in the   work   shift   and   persist   at   night.   Reduced   capacity   for repetitive work. • Late   stage:   Aching,   fatigue,   and   weakness   persist   at   rest. Inability to sleep and to perform light duties.