"For example, in any culture, it is customary to offer your help to pick a heavy item, but this act can offend your female coworker because it also indicates you don’t think women have strength."

To be honest, I'm not sure this is true. We know that we're usually out-ranked in the strength department.

There are ways to offer help that don't irritate women. For example, simply saying "Need a hand" or "Can I help?" with no condescension, is usually not going to cause offense. It's when a guy swoops in unasked, or offers help while laughing, that women get a tad pee'd off.