ERGONOMICS
Differences in body dimensions, range, movement strengths, vision and understanding - to name a few
Designing for worldwide users is part knowing standards and guidelines, and part testing. References for dimensions, geometry, material properties and functionality helps to form starting points for testing - but the rest of the user experience must be verified with the aid of testable prototypes - the earlier the better.
Testing required strength for body postures at various functions is especially important - as user strength for certain body movements can vary enormously.
Hand size: Hand size and grip variation between a 10% small and a 50% medium user
Head support: Variations in height between 10% small and 50% medium users, requiring a height adjustable head support. Upper back thickness also comes into play, requiring 30mm depth adjustment to fit 5% to 95% users.
Body dimensions: Example of design dimension matrix collated from ISO 7250-2.
Body dimension limits (percentiles) are available for countries from all continents representing the largest variations.