Powerlifting and other training (including conditioning) are not multi-taskable. It's very important to keep one's concentration and focus on the exercise. I cringe when I see people talking with each other while moving metal. Even during warm-up sets; perhaps especially during warm-up sets, when the low weight allows one to do a preflighting of the movement, check for any anomalies in mobility or weak or sore prime movers or stabilizers.
When walking short distances, cooking, or doing housework, I tend to listen to podcasts or sometimes to the audiotrack of YouTube hangouts (basically the equivalent of radio's Morning Zoo). These are ways to get some low-density information into the brainpan without distracting too much from the errands. (I also listen to podcasts on shared transportation, like shuttles. Too much entropy for anything else.)
Some podcasts I listen to (there are more; I usually only listen to a few episodes a week):
(Yes, I have a significant déformation professionelle.)
When I go for a real walk, what I call a walk-n-think, I typically listen to music, not any sources of information. The point is to think and clear the cobwebs of my mind. I find the Baroque a particularly good cobweb-solvent period. Here's a walk-n-think with a side-trip to exchange books at the SFPL:
Once in a repetitive-motion machine in the gym, for oxygenation not conditioning purposes, the main determinant of the type of content is the movement of the head, in particular the eyes.
When walking on treadmills (my preferred cool-down approach) or rowing on a machine (which for me is real exercise, but of form and rhythm, not muscle), the head moves too much to fix the eyes on a screen; as the activity itself requires less attention than the errands, freeing attention for content, my choices of media are audio lectures and audio books.
(I only run on treadmills for High-Intensity Interval Training, which is conditioning, which means it cannot be multitasked. When doing anything that stresses the body, I always want 100% of the attention to be on the exercise. I have this strange desire to avoid injury, ridicule, and absence of gains; sort of the philosophical opposite of CrossFit.)
I should clarify that I'm using "lecture" to mean all sorts of purposeful speeches, not just university lectures. I do have a number of these speeches and lectures which work out well, many of them extracted from videos of talks where there were no significant visuals (or the visuals were the dreaded "power points," which are speaker's notes not audience-centered visuals).
As for audiobooks, I've been a Platinum member of Audible for fifteen years, which means I have two new books per month, which I complement by filling up on the seasonal sales and the occasional extra purchase.
Here are a few of my latest Audible purchases:
On average I listen to around 30 audiobooks per year, some of which are re-listens.
(Yes, I re-read and re-listen to books. There are some books I read pretty much every year… Waugh, Wilde, and Wodehouse; certain Poirots and Maigrets; a few favorite Discworld pieces. There are 1000-page books I read every year, though that's just Anathem. And Cryptonomicon. And Reamde. And Seveneves, now on its second year. Guess who my favorite living author is.)
For other machines, like elliptical runners, stairclimbers, and exercise bicycles, the head doesn't move, so it's feasible to use the eyes. My old-but-trusted iPad 1.0 has seen this gym duty pretty much from the first day I bought it, which was the day it came out. (100% impulse purchase, as I was coming back from brunch and passed an Apple Store.)
Though in the past I've read books (paper books), journals (academic magazines), and magazines on paper on these machines, and have evolved to read electronic versions of these, I find that I prefer to give the eyes a break by letting them watch video instead of processing written words. I tend to watch lectures (again including speeches, but in this case a lot more real lectures) on the elliptical and the stairclimber, and to read books (ebooks with large type) only on the exercycle.
(Basically I use elliptical, exercycle, and stairclimbers in my building exercise room. It's not a "gym event," rather a "I need to take a break and instead of vegetating in front of the TV, which I no longer have service for, I can go do some movement while imbibing some basic knowledge.)
I hasten to point out that despite the déformation professionelle mentioned above, I tend to think of these books and lectures as leisure, so I keep them broadly within my areas of interest but not focussed on my actual area of work. For example, here are a few courses that I've enjoyed on the elliptical machines in the exercise room:
It's worth mentioning that real intellectual work cannot be multitasked, as indicated by the position of textbooks and research papers in the diagram. Anytime I'm looking to learn something, that requires dedicated attention, note-taking, and a block of dedicated time.
I don't mean work-related textbooks (though american textbook prices do their darndest to discourage the intellectually curious from serious study) or research papers (ditto with the gating, but public libraries and authors' own webpages are a good workaround), but even when I'm trying to learn something, say geology, our of pure curiosity, reading textbooks and research papers has been a much better experience than the materials that now pass for science popularization.
(My opinion on the decline of science popularization is well established in this blog.)
One thing I used to do at the gym (the real big gym, not the exercise room and not the powerlifting gym I occasionally go to instead of driving to the big gym) and eventually stopped due to social pressure, was to watch FoodTV network on the gym TV while cooling down on a treadmill or an elliptical, after 90-120 minutes of iron and conditioning. For some reason, those whose entire workout is 30 min of slow walking on the elliptical (what I call a Potemkin workout, still better than Planet Fatness or CrossFit) were not happy with my selection of programming.