I know a number of coworkers who spend 2+ hours a day in the car. What can they do to burn more calories and stay healthy while behind the wheel?
I am rather convinced that there is nothing productive to do relating to fitness while actually driving. For the duration they're going to be sitting in a bad position, they're going to be slightly asymmetrical with their limb usage, they're going to be sedentary.
The Inescapable Tragedy of Sitting
Here's the thing, as Joseph Stromburg summarizes for Vox:
Research has shown that increased exercise for an hour or so per day can't undo the negative effects of sitting for eight hours, any more than running a mile can erase the damage caused by a smoking habit.
The large prospective study by Alpa V. Patel, Leslie Bernstein, Anusila Deka, Heather Spencer Feigelson, Peter T. Campbell, Susan M. Gapstur, Graham A. Colditz and Michael J. Thun concluded "that time spent sitting was independently associated with total mortality, regardless of physical activity level." (emphasis mine) You can't burn calories to negate the pernicious transition to immobility that driving creates.
Those coworkers should find a way to reduce their commute, period. Live closer to work. Work closer to home. Telecommute some days.
In the meantime, they should aggressively address the specific mobility problems that driving causes. They are generally similar to the ones that sitting causes, namely hip and back dysfunction. At the same time they should take on a general strength and conditioning routine that is appropriately challenging.
If the concern is keeping up their fitness while in the car, thats not possible nor is it wise. While driving, focus on driving, not fitness.
However, if you look at this part of your question:
What can they do to burn more calories and stay healthy while behind the wheel?
If they (or you on their behalf) are interested in their calorie deficit, instead of trying to burn more, instead focus on consuming less.
Ultimately, you can't change peoples behaviour for them. If they wish to be unfit, they will. Perhaps you need to come to grips with that?
Focus on the ~14 waking hours per day. As outlined in Dave's answer, sitting for long periods is bad, no way around it.
- Where I work, I have a stand up desk with a high chair. If I want to stand up, I hop off the chair. If I want to sit, I sit my butt down.
- A few times a day I work on my third-world-squat.
- Stand up in meetings.
- Have walking meetings. If someone wants to talk to me about something, I'll usually ask if they want to go for a walk around the building while we discuss. There's no particular reason to sit in my office for most discussions.
A lot of workplace cultural norms are there only because they haven't been challenged yet. Things like standing desks, moving around a bit during meetings in a non-disruptive way, and taking a walk around the building are easy to implement.
You could re-ask the question as what can someone do who sits down in meetings for two hours a day? The answer is basically the same: focus on the remaining time and try to make those two hours be the worst, not the norm.