I do this now on our LMS for each course section but not necessarily for each assigned reading. For example, this week after students complete their reading quiz for enzyme properties we will be considering enzyme mechanisms in class. I could, for example, the evening before write a short email detailing why I want students to know well the example of the serine proteases and how it illustrates the influence of amino acid residue charges on enabling transition-state and catalysis. Then in-class we could address student concerns and explore in detail the enzyme mechanism and perhaps even have time for an application of the knowledge. Sometimes I do include an overview explanation in my reading guides to provide context for the reading assignment and what we are learning in this section of the course. But mostly I rely simply on providing for students the learning objectives for that particular reading assignment.
I am not sure that preparing a podcast is better than preparing a reading guide. Dr Bowen makes the case that a personal podcast from the instructor is more inviting. But it is still a talking head. Is that better than text? Is listening better than reading? According to Bligh, talking heads are no better than text at conveying information. But Bowen is not arguing for using these introductory podcasts necessarily simply for transmitting information to students. I get the sense that this is more of an invitation to learning. Is that done better in a podcast than inside the classroom in real-time? But then again, this is the introduction to encourage students - to invite students - to prepare for the classroom so it needs to be done outside of class. I'll continue to provide overviews of the point of the reading assignment. Even if students don't read them, at least it provides me a point to refocus myself on why I am teaching the material.
One of the things that I am finding out about myself as I work through this book is that I tend to really focus on the cognitive domain and not so much on the affective domain of learning. And this may be what causes some of the resistance I experience when I implement active learning in my classrooms. We know that learning works best when students feel invited to learn, welcomed to learn, made comfortable while learning. Of course, learning is about effecting change in students' thinking - in how they conceptualize the world - and thus will require students to move out of their comfort zone. But are there ways/approaches/strategies/considerations that better support students as they enter the learning environment in which they may need to feel uncomfortable while what they are learning does not match their mental models of the world?
Bligh, D. A. (1998). Evidence of what lectures achieve. In What’s the use of lectures? (5th ed., pp. 10–23). Exeter: Intellect.
Bowen, J. A. (2012). Technology for information delivery. In Teaching naked: How moving technology out of your classroom will improve student learning, Chapter 5. San Francisco, CA: Jossey-Bass, an imprint of Wiley. p 103-127.