At your next 5k, watch the field and pick out the 3 worst bounders (have the most up and down hip motion in their stride). When they finish ask them how much they run on a treadmill.
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I dunno - I’ve done over 70% of my running for this entire year on a treadmill, and there’s no big bounding going on. I’m running the fastest I ever have for triathlon, with the lowest mileage I ever have (I can go pretty hard on the TM with less injury risk.)
Things are going so well TM runningwise that I will likely shoot for the BQ next spring/summer (I used to be marathon runner, but never ran a ‘fast’ marathon to BQ at. Came close at the SF marathon, but that’s not a BQ-friendly course and missed by minutes.)
That is a nice snowflake story. 
Note, you are running outside way more than Sanders. There is nothing wrong with running on a treadmill. You are losing something if you are doing 100% of your runs on a treadmill though. Especially if you are trying to be world champion at an event that requires running.
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The one thing he mentions that is seriously worth consideration is the reduced risk of injury on a treadmill.
For me, when I was running high-mileage as a pure marathoner (all outdoor), I was constantly on the brink of a season-ending injury, like a stress fracture or a tendon injury. Even now, the main thing that will likely destruct my good forward motion (even at age 40+!) of running is an unexpected injury.
This is the first year that I’ve really gravitated toward bulk treadmill training, and in retrospect I do think it’s responsible for keeping me injury free despite the continued progress. It’s partly the reduced impact, but I think that might actually not be as critical as the ability to make incremental tiny progress on a treadmill, reliably.
I’ve cut 20sec/mile off a near-plateaued 40 minute tempo effort, dropping from 6:24/mi to 6:04/mi in the past 4 months by inching that speed up on notch every few weeks. I def wouldn’t be able to control the granularity of that gain outdoors, and in additoin, I know from history that when I’m running those low-6 miles for tempo runs, I’m always at a big risk for a strain, esp if I have a ‘good day’ and overdo it accidentally.
The TM has been great for keeping me in check - no injuries for me despite running my fastest TM paces yet. I really do think that incremental tiny gain is a big contributor to that.