Mass is static [in this context], but weight is a force and will apply differently based on angles. I'm no physicist but they might have got it right here.
Weight doesn't vary like that. What varies based on angle are the counterbalancing forces applied by your various body parts to keep it in place. That's vaguely similar to what the article said, so they may be basing this on an original claim that isn't nonsensical -- but if so it got badly garbled.
Well we all know holding you arm straight up or holding it out perpendicular to your body for 30 seconds are very different in terms of effort, perceived force, and pain. I think that's what they were going for.
Okay, but where did they get 20 kg / 200 Newtons / 44bs? I can see the assertion that there's zero transverse force across the neck when the head is held strait up, but how do they come up with a force greater than the weight of the head and neck? A.x cos(x) <= 1.0. Holding your neck out horizontally, the full weight of your head and neck is exerted transversely across your neck, but that's nowhere near 200 Newtons, and that's the worst case.
Giving an exact figure implies they've done some calculation, and either their understanding of the physics is way off, or their arithmetic has gone far off the rails.
Someone who remembers their physics should probably reply with actual numbers but I think lever forces are what is at play. A downward force approximate to the mass of the head (6-8kg) is applied, the neck is a lever, and the force at the other end reacts appropriately.
Wikipedia says: if the distance a from the fulcrum to where the input force is applied (point A) is greater than the distance b from fulcrum to where the output force is applied (point B), then the lever amplifies the input force.
So that says that you can get a higher output force than the input force, which in this case is the force applied due to gravity and mass (plus your walking motion).
