For product interaction, reach & stretch ability can be broken down into the ability to move one or both arms in two perpendicular directions, as shown in the figures opposite.

Most products require the ability to put one hand in front of the body to use them. Where possible, requiring both hands to be placed in front of the body simultaneously should be avoided. Using products should be possible by reaching either the left or right arm. Requiring people to reach above their heads is more demanding than requiring them to reach out in front.

Reaching out to the sides is used to access items while sitting at a desk, or to put on a jacket. The further the arm has to reach out to the side or back, the more difficult it can be to reach items.