I remember reading somewhere a study was done in a closed environment (IIRC a habitat within a cave) that ran a 25 hour day cycle using lighting to demarcate the time shift, and the result of that test was that the subjects were able to adapt to this schedule. If that was the case, adapting to a 24:40 day wouldn't seem to be much different - there may be an orientation period but something is tickling my brain that the study proved we can adapt to such a schedule without ill effects.

I'd need to do some research to find the original study.

I do know (from my various travels) that changing your daylight/night orientation from what one is normally accustomed to can create some sleep and performance issues initially; while this is not extending the planet rotation by 44 minutes, there are similar spans of "adaptation" needed to acclimate to both the skewed light cues and sleep pattern adaptation, so one can function during extended dark periods and sleep when light periods are similarly extended. (Think of someone traveling from Albuquerque, NM to Fairbanks, AK, or Petersburg, Russia...or vice versa.)

I think the stated problem is that the people trying to live and work on a Martian day schedule are still surrounded by the Earth lighting and rhythm cues - so when they get off their "shift" they're at a different part of the day than the day before - instead of seeing the sun set, they may be in mid-night, or full daylight. Just like having "rotating" shifts - some people can adapt to it, but not many. I suspect that once you are fully on the "Martian cues" instead of switching back and forth constantly, the human body will stabilize pretty quickly.

It's fascinating to think that humans are that unadaptable

Interesting. I never considered this as a problem to over come. Surely we could adapt to the 24:40 day.

In Kim Stanley Robinson's Mars trilogy, the extra time each day was a like a bonus, a little extra time each day at the expense of slightly fewer days in your life. This suggests that little extra time may be a curse.