The ‘actuator lugs’ on the Newton Running Shoes

Just yesterday I had an email asking my opinion on the so called ‘actuator lugs’ on the Newton running shoes and as there was no research on them, my reply was essentially ‘no opinion‘. Not 24hrs after replying there is no research, there is now some research (see below). Before I replied, I did go to the Newton website to check if there was any research there before replying and was led to the section of the site on science and of course all the usual woo, quackery and snake oil alarm bells went off in my head, as there was no science there at all! At least by my definition of science, in that there is no scientific evidence to support the claims being made.  The ‘lugs’ are essentially elevations or protrusions under the metatarsal heads that expand out sideways under load and are claimed to return energy. The rationale behind the principle makes sense and is plausible, but that does not make it ‘science’, hence the alarm bells that go off in my head when they claim ‘science’. The company do claim some internal testing that they do lower the impact loads and increase the energy return.

newton

From what I can tell, opinions are divided on their effectiveness; some testimonials say they are great; other anecdotes are that they don’t like them (which is why we need science to make more generic recommendations). There have been concerns about the lugs increasing the risk for plantar plate dysfunction, but I not so sure of that.

Here is the research that was just published:

Influence of midsole ‘actuator lugs’ on running economy in trained distance runners
Matthew F. Moran & Beau K. Greer
Footwear Science; Volume 5, Issue 2, 2013
Introduction: Previous investigations reported the influence of running shoe design on running economy (RE) and determined that both shoe weight and midsole properties (hardness, stiffness, comfort) can alter RE. External forefoot actuator lugs have been reported to provide enhanced energy return during shoe mechanical testing, but it was unclear if this design feature would provide any improvement of RE. The current investigation measured the effects of external forefoot actuator lugs on RE in 12 highly-trained male distance runners during four submaximal running velocities.
Methods: All runners voluntarily completed a maximal graded exercise treadmill protocol followed 5–7 days later by eight randomised 6 min submaximal level-grade treadmill runs with two randomised footwear conditions (WL = with lugs, WOL = without lugs). Oxygen consumption, heart rate (HR), rating of perceived effort (RPE), and sagittal plane high-speed video were collected. RE (metres run per millilitre O2 per kg of body mass), stance duration (ST), stride rate (SR), and foot strike (FS) were computed for each trial. Data were analysed with factorial repeated-measures analysis of variance (ANOVA).
Results: RE, averaged over all submaximal velocities, was significantly greater (p < 0.05) in the WL condition (4.96 ± 0.12 m·ml−1·kg−1) as compared to the WOL condition (4.91 ± 0.10 m·ml−1·kg−1). Only one subject displayed a lower RE in the WL condition. No significant differences were found between HR (p > 0.05), ST (p > 0.05), or SR (p > 0.05) between footwear conditions, but running in the WL condition lowered RPE (p < 0.05).
Conclusions: The presence of external forefoot actuator lugs improved RE by ~1%, although the mechanisms explaining this improvement are not clear.

Basically, they did find the running economy was improved in the shoe with the actuator lugs by a small, but still statistically significant amount. Given that the effect sizes were also small, I am concerned about the practical significance of that small change. Of note was the subject specific variations: for running economy, one participant was more economical without the lugs; one no difference and 10 were more economical with the lugs. We are seeing this more and more in the response of individuals to different technologies in running shoes. The study was also an acute intervention and the differences reported may or may not be applicable to those who are habituated to the lugs.

The mechanism behind the improvement in running economy can only be speculated in the absence of evidence, but Newtons marketing mentions that some runners liken running in these shoes as to a ‘trampoline’ effect which may increase the energy return, but that is only speculation.

As always, I go where the evidence takes me.

Moran, M., & Greer, B. (2013). Influence of midsole ‘actuator lugs’ on running economy in trained distance runners Footwear Science, 5 (2), 91-99 DOI: 10.1080/19424280.2013.792878

Last updated by .

About Craig Payne

University lecturer, runner, cynic, researcher, skeptic, forum admin, woo basher, clinician, rabble-rouser, blogger, dad. Follow me on Twitter, Facebook and Google+

,

7 Responses to The ‘actuator lugs’ on the Newton Running Shoes

  1. Thomas Twomey May 24, 2013 at 2:05 am #

    Great to see some research done in this area. As I mentioned to you in these realms before I am very interested in the influence of Hoka One One on running economy and this study is somewhat related. The topic of Newton’s is interesting, I think from personal experience and anecdotes I have heard the lugs do more damage than good in many cases. I think if they just had overall more cushioned forefoot and maintain 2-3mm heel-to-toe drop they would have a more comfortable all round shoe but then they would not have their point of difference from other brands I guess. Never the less it is now good to have some science to refer to when selling these shoes.

  2. Peter Larson May 28, 2013 at 9:38 pm #

    Do you know if they controlled shoe weight in the comparison? Haven’t received my issue yet.

  3. Craig Payne May 28, 2013 at 9:46 pm #

    With lugs it was 254.8+/-18.8g
    Without lugs it was 240.3+/-14.3g

    They did not control for the weight difference, but if did, then assume the the ~1% difference would be minutely greater???

    (emailed you the paper)

    Here is what they said:
    Shoe mass was not controlled in this study as the removal of lugs for the WOL condition resulted in a lighter shoe by 5.7% (15 g per shoe). The relationship between shoe mass and energy cost is intuitive; energy demands during running are greater as shoe mass is increased (Frederick et al. 1982). Since the WL condition was slightly heavier than the WOL condition, the RE improvements reported for the WL condition were slighter diminished by the heavier shoe. Frederick et al. (1982) reported that 135 g shoe mass reduction equated to approximately a 0.7% energy savings. Since the shoe mass differential was small compared to this previous
    report, it is unlikely that a 30 g combined difference had a substantial influence on the study’s results.

  4. Nick Barkley May 30, 2013 at 2:51 pm #

    I bet the forefoot lugs increase the longitudinal bending stiffness of the MTP joint.

    Shoes with similar stiffining features like the sprint web technology found Adidas Tempo or forefoot trusstic system in the Asics DS Trainer probably produce the same effect.

  5. Dr. Steven King June 14, 2013 at 11:46 pm #

    Aloha,

    If increaseing the longitudinal bending stiffness of the MTP joint is important perhaps we should look into building our footwear with more advanced composite materials such as carbon fiber. There is a large difference in modulus of elasticity between rubber/foam systems and advanced composite systems.

    Don’t Get Weft Behind Its Warp Speeed Ahead with Advanced Composites.

    A Hui Hou,
    Steve

    Managing Member Kingetics LLC
    Co-Principal Investigator SBIR A11-109 “Advanced Composite Insoles for the Reduction of Stress Fractures.” US Department of Defense and Army’s Medical Research and Materials Command
    ASTM F13 Committee on Footwear Safety and Traction

  6. Beau June 17, 2013 at 4:41 pm #

    When I referenced the potential lack of practicality of a 1% improvement, Will Hopkins of Sportsscience (he’s somewhat of an out of the box statistics guy) told me that a 1% difference in economy equates to about three additional medal finishes for every 10 races in otherwise equally matched elite runners. However, switching from the relatively heavy Newton to a 4 ounce racer would get you about the same benefit…

  7. Ian Adamson November 22, 2013 at 4:57 pm #

    Craig Payne wrote: “The ‘lugs’ are essentially elevations or protrusions under the metatarsal heads that expand out sideways under load and are claimed to return energy.”

    As a matter of clarification, the lugs on Newton Shoes cause elastic deformation on the supporting membrane on load. The lugs themselves do not deform appreciably. An accurate analogy is pushing down on a trampoline, although this is upside down as the lugs push up into the trampoline membrane. The reason the lugs protrude is to facilitate compression of the technology and the resulting travel = reduction of loading rate during contact / loading phase of gait. All midsole cushioning technologies compress, however only springs and membranes do so without dissipating most of the kinetic energy as heat energy.

    The membrane material is highly elastic and resilient Dupont Hytrel which is also stable over a wide range of temperatures (-40 to +270F.) Midsole EVA by comparison is dissipates impact as heat when the air compresses in the foam. In addition it moves to provide useful return of kinetic energy to the runner (i.e. Ep to Ek.) Midsole EVA is temperature stable between +20 and +120F. It actually falls apart around 150F which has ramifications if you run on a hot road – just look at what happens to EVA shoes at eh Badwater Ultramarathon where the road can reach 190F.

    Another misunderstood feature of Newton Shoe technology is the structure between the ground and the foot, which consists (from the bottom up) of the lugs, membrane, semi-rigid chambers to accept the lugs, EVA support layer, flexible metatarsal plate and EVA top cover. Unlike regular foam shoes, this construction prevents the metatarsals from collapsing, facilitating splay of the metatarsals on load (in conjunction with flexible panels in the upper) and afferent feedback – also why people think they are feeling the lugs, when they are actually feeling the top plate.

    If you want real science, MIT is in the final review stages of a study they started in 2008 looking at the effect of Newton Shoes on running speed compared to regular shoes. High confidence level, solid science. Skeptics of Newton Shoes may be surprised. There are several unpublished studies with similar outcomes for various Universities around the world. These help us understand the neuromuscular and kinematic effects of the footwear and allow us to maintain continual improvement of the technology.

    Full disclosure: I am the director of research at Newton Running

Leave a Reply