So physically demanding that it is inconceivable that any woman could ever be capable of doing it?
So physically demanding that the very best woman could always be bested by a ready, willing, and able man.
Moreover, even if you were in a situation where you could find a job where a rare woman could manage to be the best available candidate, the difficulty associated with employing that woman for the task really would outweigh the marginal benefit of choosing her over the next best qualified man.
Your question betrays a mode of thought very common in modern circles, that the decision about who should get a job should be based on who is best for the job. However, that's wrong, and dangerously so. In the military, it should be based on what is the best team that can be assembled, not on the individual capabilities of a given candidate.
But paragraphs like the one above often give people some opportunity to insist that the real problem here is the bigotry of the other members, so I want to emphasize the nature of my objection. When it comes to physically demanding jobs, like eighteenth century infantryman or WWII era tank driver, it is conceivable that you might find a woman who can meet the minimum requirements, but there would always be a better qualified man. For slightly less physically demanding jobs, you might find a case where the best qualified available candidate really is a woman, but that woman would be only slightly more qualified than a male candidate that was available, so the tiny benefit that could be gained from giving the job to the woman in that role would be offset by the disadvantages of employing one woman out of hundreds in that role. The good of the unit must take precedence in that case over what's best for one individual.
In the modern military, there are undoubtedly many things that are not traditionally women's' roles, but which no longer require the physical strength the corresponding role once did, and so it seems reasonable to believe that the quality of the unit could be improved by employing women. If so, it should be done.