Rodger Kram wrote:
Hi
I'm the senior author of the scientific article and I'd like to clarify a few things.
1. Is this a new study? Yeah, it was just published earlier this month. The data were collected in summer/fall 2019. The university shut down in 2020 which prevented us from collecting the biomechanics data as we had planned. The first author, Clarissa Whiting, started med school in 2020 and the middle author, Wouter Hoogkamer started a faculty position at U Mass Amherst in 2019. We held off publishing for a while, hoping that the lab would re-open. We decided to just publish what we had.
2. Grade: We chose 3 DEGREES (about a 5% grade) to approximate the hills of the Boston Marathon, the hilliest marathon major on roads.
3. Speed: We chose 13 km/hr because up a 3 degree hill, the rate of oxygen consumption at 13 km/hr is just about the same as 6:00 min/mile pace (16 km/hr) on level ground. So, about a 2:36 marathon pace.
To measure running economy, the subjects must be sub-maximal, i.e. ~ below lactate threshold.
It is feasible in Boulder to find a nice group of 2:36 marathoners. It is not easy to find a group of 2:20 marathoners who are willing to come to the lab.
Our previous studies (i.e. the first one from which the 4% got its name), studied level running at 14, 16 and 18 km/hr and the per cent savings were the same at the three speeds. In the present study, we wanted to study the effects of incline/decline, the level condition was just a sanity check and we found the same thing was we (and others) did in 2017, 18 etc.
4. Shoe choices: We already had the fresh Vaporfly 4% shoes and Streak 6s. The 4% savings have been replicated by several other studies and to my knowledge, nobody has yet published a study of the Next% or Alphafly shoes. There is one study hopefully forthcoming that compared 7 different shoes to the Alphafly and Nxt%2. That paper was discussed on these boards maybe 2 months ago. The Streak 6 shoes are a bit outdated, but we needed some shoes for comparison and since they were the de facto standard for the infamous 4%, it made sense to use them since our main question was whether the 4% would hold up or be exaggerated up or down hills. We could have used any shoes for a comparison. For examples we could have used a pair of classic Nike Cortez and maybe we'd find 12% savings. Our question was whether that would change to 11 or 13% up/down hills. Since Nike seems to make the same Nike Cortez shoes every year, I do recommend that they would be a nice "gold standard" to use in future studies. Any other model we choose will become extinct in a year or two.
5. Yes, as we note in the paper, studying steeper inclines/declines would be interesting and more relevant for trail running/racing. Science is incremental.
6. Are we shills for Nike? Nike pays me very modestly as a consultant and they have supported our research in the past. This study received no separate funding from Nike. Clarissa Whiting has no Nike affiliation. Wouter Hoogkamer has been supported by Nike in the past when he was my post-doc, he has done and is doing research supported by Saucony and Puma in his own lab. Some folks accused us of being shills in 2017 and our findings have been since confirmed by at least 4 other independent labs since then.
7. We and just about everybody else we ask/asked (Geoff Burns, Alex Hutchinson...) have/had hunches about how the results would come out. Most predictions were wrong. Intuition is fine, but experiments are how we gain knowledge. Everything is clear and obvious in hindsight.
OK, time to put on my Nomex suit.
rk
Rodger Kram, Ph.D.
Associate Professor, Emeritus
Integrative Physiology Dept.
University of Colorado Boulder