Hours worked in research vs teaching professorships Are there any studies that have compared the number of hours worked by faculty members who are teaching-focused vs. those at research intensive institutions?

I have the impression that faculty that balance teaching and research tend to work longer hours and on weekends more than faculty who do not have any research obligations. I don't know where I picked this idea up and I'm suspicious that it is biased and based more on opinion than fact.

Any studies/surveys out there to support / refute this idea?

I'm interested mainly in science departments in the USA.
Looks like Jacobs and Winslow (2004) address this issue.

"the average workweek for full-time faculty exceeds fifty hours. These long workweeks are characteristic of all groups of faculty, irrespective of rank and institutional type. In other words, assistant, associate, and full professors all work in excess of fifty hours per week, as do faculty at research, liberal arts, and comprehensive institutions."

Jacobs, J. A., &amp; Winslow, S. E. (2004). Overworked faculty: Job stresses and family demands. The Annals of the American Academy of Political and Social Science, 596(1), 104-129.