Sedentaristic courses shorten lifespan, reduce end-of-life quality? More for seated students than standing instructors?

"Stand Up for Fitness" for BETTER, longer life: 
DON'T sit more than 20 mins(?) without movement break
DO include multiple weekly sessions of aerobics + balance + weight training


That's my synthesis of recent advice accumulating from many sources - especially the article cited below. The questions that follow were prompted by that article and my search for more amusing, challenging, and memorable ways of communicating important information that is too often ignored.

1. Doesn't this anti-sedentary advice conflict with our customary practice of requiring students, audiences, meeting attenders, restaurant patrons, bus passengers, etc. to remain seated for at least an hour per session? 
2. Do traditional face-to-face classroom sessions shorten the lifespan and reduce end-of-life quality for students while ergonomically favoring instructors? 
3. Do synchronous online course sessions shorten the lifespan and reduce end-of-life quality more equitably for students AND instructors? Same for asynchronous course activities?
4. Is the 20 minute maximum for staying seated significantly more beneficial than a 50 or 60 minute maximum?  
5. Why in the traditional classroom, is the instructor often the only one in the room permitted to stand or move about?  Both in the earliest grades and in higher education, we expect students to remain seated and mostly immobile until the instructor gives permission to depart.

- Excerpts, quotes, references from "Don't Just Sit There," by Gretchen Reynolds, The New York Times, "A version of this news analysis appeared in print on April 29, 2012, on page SR8 of the New York edition with the headline: Don't Just Sit There"
The full-text of Don't Just Sit There charmingly and clearly summarizes rapidly accumulating evidence
that lengthy sitting sessions are harmful but can be made much less so by interrupting them with brief non-sitting activities. The article urges that we add non-sedantariness to the widely advised practice of daily and weekly schedule of aerobics (at least 30 mins of brisk walking per session, at least 4 or 5 sessions per week) AND several weekly sessions of balance training and weight training.
Here are the 2 closing paragraphs:

"So every 20 minutes or so, I now rise. I don't have a desk treadmill; my office is too small, and my budget too slim. But I prop my papers on a music stand and read standing up. I prowl my office while I talk on the phone. (I also stand on one foot when I brush my teeth at night, which has little to do with reducing inactivity but may be one of the more transformative actions I've picked up from researching fitness. My balance and physical confidence have improved, and my husband is consistently amused, which is not a bad foundation for marital health.) 

"I run for three or four miles most days, too, and grunt through 20 push-ups most mornings. There are health and fitness benefits from endurance and weight training that standing up can't match. In particular, aerobic workouts have been shown to improve brainpower, and I shudder to imagine the state of my memory if I didn't run. But I'm not planning any marathons (been there, done that, walked down stairs backward for days). I want foundational health. I want my insulin levels in check and my fat-fighting enzymes robust. I have plans for those extra 18 months of life span that not sitting might provide."

IMAGE selected by Steve Gilbert 20120430
Photo of person "Stand up paddle surfing in Okinawa" 6 July 2009, author/source:  " babibox's file; BoBA"
http://upload.wikimedia.org/wikipedia/commons/a/ad/Happy_Stand_up_paddle_surfing.jpg
http://commons.wikimedia.org/wiki/File:Happy_Stand_up_paddle_surfing.jpg
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