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Impact G question

Alan Grose

July 02, 2015 01:51

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I've always assumed that the impact forces of running on a treadmill would be less than road running.

I did a series of treadmill runs this week using just the treadmill and a Lightspeed Running device. It has the effect of making the runner up to 35 lbs lighter. That's not me in the picture. My hair isn't that dark, but I have more of it.

The runScribe results were pretty amazing. My usual Stride rate is around 170 and Footstrike 4-5. I was able to get it comfortably up to 200 and Footstrike of 14. The Lightspeed seems to provide a little buoyancy in addition to weight loss.

The surprise was the Impact G numbers. I've been seeing 7g on average recently, but was consistently seeing 12-13g on the treadmill. This was the case with both Heel and Lace mounted runs.

I'm not questioning the accuracy of the runScribes, but wondering if it's normal to see these high G numbers on a treadmill. One of the Physical Therapists did a few runs with a runScribe and saw numbers in the same range. 

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2 comments

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  John Litschert July 03, 2015 00:23

  I've seen a similar relationship to yours although not so dramatic.  8 to 10 outside and 10 to 12 on a treadmill.  Pace will affect these numbers so make sure you are comparing similar speeds.  As I go faster my G's go up no matter where I'm running.  Typically in the 11 to 13 range.

  I don't really have a good explanation for the increased G's while you are on the treadmill.  Were you seeing the 12-13g while running at 200 st/min?  Sometimes mid foot striking can generate higher Gs than rear foot so that might have something to do with it as well.

  The lightspeed looks like a pretty interesting contraption.  Do the vertical poles telescope up to help create different amounts of bouyancy.

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  Alan Grose July 04, 2015 13:26

  The highest G impact numbers on the treadmill were at a higher cadence and faster pace than I normally run.

  13.31 G's 202 Stride Rate 7 mph with an approx. 35lb weight reduction.

  11.2 G's 184 Stride Rate 6 mph with weight reduction

  9.2 G's 174 Stride Rate 6 mph no weight reduction

  This morning on the street 6.7 G's 166 Stride Rate.

  The 4 straps attach to the horizontal bars. Those bars can be raised or lowered to adjust the percent body weight reduction.