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Ten peer-review articles [1-10] have studied the physiological response of using oval vs. circular chainrings. I report a summary of their conclusions.

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Five papers [1-5] reported improvement in power delivery. Three discussed general improvements [1-3] , and two identified only an improvement for short sprint activities [4].

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The remaining six articles demonstrated no benefit [5-10].

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Looking at it in the inverse, none reported a disadvantage to having an oval chain ring.

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Experiment:  The time and cadence were measured (Garmin Edge 520) for  3-mile road relatively flat circuit (<100 ft of elevation change) on a mountain bike (S-works Epic) with the same cassette gear selected, power held constant at 275W (as measured by Quarq's powermeter). Measurements were repeated 3 times for each chainring and averaged.

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Results:

Chain ring                                       Time                 Cadence

36T circular  (SRAM sync2)             8m 24 +/- 3s     70 +/- 1rpm 

34T oval (Rotor Q-ring 34T)             8m 31 +/- 2s     72 +/- 1rpm

34T circular (SRAM sync2)              8m 35 +/- 2s     74 +/- 1rpm

Conclusion: The main conclusion is that 34T oval is not equivalent to 34T circular, rather it is equivalent to a larger circular chainring (approximately 35T). Research studies maybe could consider comparing oval to multiple circular chain rings to determine the effective equivalent for any comparison. The differences in performance for this brief study are associated with the difference in cycling technique at different cyclist cadences, and the chainring selection effected cadence. There was no clear benefit nor negative to an oval chain ring.

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References:

1. Hintzy & Horvais. Non-circular chainring improves aerobic cycling performance in non-cyclists, JournaEuropean Journal of Sport Science Volume 16, 2016 - Issue 4 Pages 427-432

2. Hintzy et al. Effects of a Non-Circular Chainring on Sprint Performance During a Cycle Ergometer Test, J Sports Sci Med. 2016 Jun; 15(2): 223–228.

3. Mateo et al. Effects of the Q-Ring non-circular pedaling system on sprint performance in the BMX cycling discipline, J Sports Sci Med. 2014 Jan; 13(1): 97–104.

4. Hue et al. Enhancing cycling performance using an eccentric chainring Med Sci Sports Exerc. 2001 Jun;33(6):1006-10.

5. Cordova et al. Physiological Responses during Cycling With Oval Chainrings (Q-Ring) and Circular Chainrings, J Sports Sci Med. 2014 May; 13(2): 410–416.

6. Sinclair et al. The effects of conventional and oval chainrings on patellofemoral loading during road cycling: an exploration using musculoskeletal simulation, Sport Sci Health 14, 61–70 (2018).

7. Strutzenberger et al. Effect of chainring ovality on joint power during cycling at different workloads and cadences,  Sports Biomechanics 204 April, 15:4, pages 97-108.

8. Cordova et al. Physiological Responses during Cycling With Oval Chainrings (Q-Ring) and Circular Chainrings  J Sports Sci Med. 2014 May 1;13(2):410-6.

9. Hull et al. Physiological response to cycling with both circular and noncircular chainrings Med Sci Sports Exerc. 1992 Oct;24(10):1114-22.

10. Ratel et al. Physiological responses during cycling with noncircular "Harmonic" and circular chainrings, European Journal of Applied Physiology volume 91, pages 100–104(2004).

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