Apple MacBook Pro (15-inch, 2.53 GHz, Mid 2009) - Manual (Page 72)

72 Chapter 5 Last, but Not Least
Understanding Ergonomics
Here are some tips for setting up a healthy work environment.
Keyboard and Trackpad
When you use the keyboard and trackpad, your shoulders should be relaxed.
Your upper arm and forearm should form an angle that is slightly greater than a right
angle, with your wrist and hand in roughly a straight line.
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