Oval Chainrings : Do they work? What's research say?

The main idea: Oval chainrings are meant to make the chainring larger during the power phase, and take advantage of the extra potential power generation possibilities when we're at our strongest in the pedal stroke, and make the chainring smaller when we're in the weaker sections of our pedal stroke. You'll also see it referred to as eliminating the dead spots in a pedal stroke. On the surface it seems like a very simple and useful component change -- after all, it's well documented that a normal pedal stroke has portions, like the back side or recovery aspect where we don't generate power.But the big question is "Do they help?" Do these non-round chainrings improve a rider's power output or efficiency, either mechanical or metabolic? As with many things, the answer isn't very simple. The good news is that there's a fair amount of research looking at these so we have some decent information to judge them by.Starting with the manufacturers that make these rings, let's look at the evidence they present on their website. I skip all the marketing garbage and always look for peer reviewed journal articles that might be referenced, because in-house testing is terribly unreliable. Aero wheel manufacturers wind tunnel test and report the data from yaw angles that best support their wheels characteristics, frame manufacturers test the stiffness or vibration modulation of their bikes in a way that puts their best foot forward, it makes sense that a chainring manufacturer isn't going to be any different. They're not going to display or show you the tests that disprove their product's selling points.So I started with Rotor who makes the Q-Rings, and they have five links to studies and after reading and researching each one here's what I've found:The first study is by far their best foot forward. It seems like a pretty well thought out study. It actually has a decent read of the available literature heading into the experiment, even citing the studies that showed no effect with the use of non-round/Rotor chainrings. It was a little light on participants, they only used 8 subjects and an N=8 isn't particularly strong. They also used experienced cyclists because inclusion in the study required cycling at least 8 hours per week, a higher than average VO2 max (55 ml/kg/min), a Category 1-3 or Collegiate men's A racing license and be between the ages of 18-39 (the subjects, all male, ended up being age 19-24 years old). On the surface this may not seem like a big deal but when there are a few studies out there noting that asymmetric rings were only helpful to young, fit, healthy, advanced racers, this doesn't do much to widen the scope for usefulness of these cranksets. Additionally they were testing the for an all out 1-km time trial effort -- not exactly what you'd call the typical rider's effort or concern. But the results were good and they did show greater power, faster speeds, and lower times over 1 km. The best we can draw from this is that asymmetric rings can help if you're a young fit male racer over a very short and intense 1 km effort.The next four studies provide us with less:#2 relies on completely subjective reporting of test subjects on how much effort they feel like they're having to do as well as how much stress it feels like their knees are subjected to, but without any objective measures.#3 was not a published study but merely preliminary data from Francesco Conconi back in 1998 that showed promising data but was never expanded on or made it into an actual study to my knowledge.#4 Is a decent study of the metabolic effects of Rotor rings during a sub-maximal exercise. They measured heart rate, lactate concentration, and systolic blood pressure. This study also used very young subjects -- they were all male and age 17-20 -- and there were ten of them tested. For the Q-rings their systolic blood pressure, heart rate and blood lactate were all lower over the course of the 15-minute sub-maximal test. A couple things that weren't adequately explained:

• what the power output during the graded sub-maximal test was for these athletes -- they only noted that they pedaled for 10 minutes at a 3% incline and then 5 minutes at a 4% incline (with a 5-minute warm-up and cool down)
• why is the baseline number for lactate and systolic blood pressure at the "0" point in the recording of data not the same? If we're measuring these things at the begining of the 5-minute warm-up phase, shouldn't they be the same? And if they're not shouldn't this be taken into account when we see the curves remain separate through the testing? After all, the pulse rate shows the least difference between the curves in ths study (the largest differences is during the warm-up phase, not during the testing phases) and they ostensibly start at the same zero point for the subjects

So the more I read this study, the more questions I have about it. I'm not saying it's a bad study, but there are things that need to be clarified.#5 is actually just a training journal of sorts, where a single rider has noted their overall time and heart rate over the course of the same 30-km cycling loop. Interesting, but not research.I also went to the Osymetric website and looked at the research they had listed. The first study listed was from 1993 and a summary or poster presentation of it was badly translated into English so it's very difficult to discern what exactly it says with any reliability. The next three studies were broken links so we don't know what they're referencing.So I dug through the research a little and came up with 8 studies that looked at the efficacy of non-round chainrings. A ninth appeared to be about eccentric chainrings, even talking about non-round chainrings in the introduction but then they broke down the equipment being tested and it became clear they were testing an eccentric crankset which is something much different.Of the eight studies six found no significant difference between the non-round and round chainrings being tested while two did find supporting evidence. One of these tested non-cyclists and the other tested the asymmetric rings with cycling track specialists on a 1-km all out effort.It would take too much time to go through each study in depth, but I provided a link to each of them with a few notes about the setup of each and the pertinent information from the results section of the study. I can't provide links to the full articles since I don't want to violate the publishing rights, but the links below will take you at least to the abstract for each.

What did we learn about asymmetric chainrings?

So let's cut to the chase....do oval chainrings help? The answer to this is "maybe" or "it depends". (My readers should be used to this highly unsatisfying answer)Of course if you were to look at the manufacturers websites you'd assume that they absolutely do help, but unfortunately it's not that cut and dried.Based on my read of the literature I would say that the more experienced a cyclist you are, the more high effort riding and racing you do, and perhaps if you partake in short intense races then oval chainrings might help you. There's likely to be a learning curve for them, but I think that this is pretty shallow -- based on what I've seen you shouldn't expect to  become significantly more efficient with them three months down the line compared to a typical 3-week break-in period.If you're a cyclist who doesn't ride very aggressively and you spend most or all of your time in submaximal training zones, then I think your chances of benefiting from oval chainrings are fairly limited

Research about asymmetric chainrings

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3990898/     2014 study with 12 subjects. Measuring variables over short intense efforts with highly trained subjects. "These findings indicate that the oval chainring design, presented here as “Q-rings”, did not significantly influence the physiological response to an incremental exercise test as compared to a conventional chainring."https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3918574/ 2014v study looking at 16 BMX racers."there was no significant difference in power output for the Elite group, while the Cadet group revealed larger peak power with the circular chainring. Neither lactate level, nor heart rate showed significant differences due to the different chainring used. The non-circular chainring improved the initial acceleration capacity only in the Elite riders."https://www.ncbi.nlm.nih.gov/pubmed/26406359     2016 study looking at 10 male, non-cyclists. "Results showed a higher maximal aerobic power attained with the non-circular chainring, which could be explained by a significantly lower energy expenditure during the first increment at 100 W. It could be hypothesised that the use of the non-circular chainring allowed saving a small part of energy expenditure throughout the test, allowing the exhaustion of the subject at a higher increment for a similar maximal energy expenditure, in comparison with a CC. Although this improvement is obtained only for non-cyclists, it allowed highlighting the link between cycling equipment modifying the pedalling motion and physiological responses."https://www.ncbi.nlm.nih.gov/pubmed/12955523     2004 study looking at 13 male "sub-national" cyclists (non-elite). "comparison of the physiological response in this study did not translate into an advantage of the Harmonic over circular chainring during submaximal and maximal pedaling in trained cyclists."https://www.ncbi.nlm.nih.gov/pubmed/1435158     1992 study of 11 male cyclists. "None of the physiological variables including rates of oxygen consumption showed significant differences among the chainrings. Thus, the gross efficiency of cycling was not improved by any of the noncircular chainrings. For cycling events where efficiency is a determinant of performance, the noncircular chainrings do not offer any advantage over round chainrings."https://www.ncbi.nlm.nih.gov/pubmed/1601563     1992 study of 7 racing and elite cyclists. "The results indicate no significant difference in any of the parameters measured between the two chainrings for any of the experimental conditions. The data indicate that the noncircular chainrings used in this study were not more efficient than the standard circular chainring for trained cyclists."https://www.ncbi.nlm.nih.gov/pubmed/21266731    2010 study of 9 male cyclists looking at 10 km time trial performance. "Elliptical chainrings do not appear to provide a performance benefit over traditional circular chainrings during a mid-distance time trial."https://www.ncbi.nlm.nih.gov/pubmed/11404667    2001 study that references an eccentric chainring, but what it appears is that they were testing an eccentric crank which is a much different thing. "The eccentrically designed chainring was made of two crank arms sliding into each other, with the inside arm fixed on the center of the arm of a circular chainring and the outside arm sliding along the inside and revolving around an elliptical cam."This is clearly not just an oval shaped chainring that they're testing."We concluded that the eccentric chainring significantly improved the cycling performance during an all-out 1-km test. Further testing with indoor cycling specialists performing on a velodrome would be helpful to define the maximal possibilities of such a chainring." Again, not the same thing as what we've been discussing.https://www.ncbi.nlm.nih.gov/pubmed/16846753  2007 study looking at 12 cyclists in an all out 1-km test.     "We have interpreted our results cautiously and suggest that the subjects who had greater lower limb muscle volume and greater calf muscle volume, seem to have had a significant advantage in performing with the eccentric chainring. Further testing with track specialists performing at national or international level would be helpful to define the maximal possibilities of this chainring."