As an interesting point, in an old telephone company I worked at early in my career, there was a very specific rider in everyone's employment agreement that stated that the salaried, non-union employees could be expected to take on some union work in the event of a strike. This was not only allowed legally but enforced. Friends of mine in the research lab actually got a kick out of ending up working on telephone poles during a strike.

It's a mixed bag - no employer should ask you to do something that is dangerous to you - and if you had a bad back, or other condition, you should neither be expected to do it, nor penalized as "not a team player" for not doing it. That said, the norm is that some level of physical labor may be expected from some employees who traditionally do non-physical jobs because it's just not a perfect world. If you were in a state where you couldn't safely help, then you should have every right to mention this privately to your manager and be opted out.

The more polite way to handle it would be to:

• Send out a call asking for volunteers, preferably being cool about it and offering something nice but not expensive to helpers (like a free lunch).
• Send it to everyone, don't discriminate
• Give people advance notice, so they can bring grubby clothes or anything else appropriate to an unusual task.
• Don't assume who should help due to age, or gender, and don't discriminate against those who may not volunteer due to disability.

It may be worth pointing out to the office that this approach may yield more enthusiastic volunteers, better office spirit (it's nicer to volunteer than feel obligated) and gives a more easy going way of omitting those who would be injured if they helped.

Many offices just don't think ahead, it's not malicious, just thoughtless.