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.
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