OK -- It is a persistent myth that 'perfect circles' or 'technique training' w ill appreciably improve power, speed, or any other measurement of real cy cling efficiency. USAC recently did a fun webinar called 'mythbusters', m odeled in part after the Discovery TV show, and one they addressed was th e perfect circles bit. The presenter was Steve McGregor, PhD of Eastern M ichigan U. and USAC. As Steve said, pros pedal in squares, not circles.
He then presented data to prove it -- specifically invoking Ed Coyle's wo rk (see Coyle EF, FeltnerME, KautzSA, Hamilton MT, Montain SJ, Baylor AM, Abraham LD, and Petrek GW. Med Sci Sports Exerc 23: 93-107, 1991.)
You can google or go to http://www.smartttraining.blogspot.com/ and see f igure 1 for a different article that references the same study - and it's the chart that tells the story best. Note that the maximum torque is dev eloped at 90 deg from TDC - the horizontal part of pushing down. The full study looks at professional and ranked amateurs. Measurements were also done with people consciously trying to pedal in circles. Minuscule change in torque accomplishes in 'pulling,' and some potential loss of overall ability by using energy in ways that did little to really help - a net ne gative.
The upshot is that the studies - with real metrics - show that best pedal ing is using max power on the normal down stroke. It's muscle (fibre type and Lactate Threshold) that govern total power output. The best way to improve 'efficiency' is to include shorter intense workou t in the mix. Hills, sign-post & town line sprints, and working to push y ourself above your current 'max efforts' to raise the lactate threshold - the point (at or slightly below ~90% of max heart rate) where your muscl es are generating waste faster than the blood can flush it out -- it's no t actually lactic acid, but that's a whole 'nuther story. Raising LT allows you to do more work (power over time). Beyond the point of smooth pedaling (not stomping, choppy action), striving for elegance won't help on that next hill.
What's wild is that this myth persists -- note that Coyle's work was publ ished in 1991 ! -- in spite of consistent additional study that supports & affirms the original testing.
It's like the apocryphal story (one that may not be true, but should be b ecause it makes a good point) about Jaques Anquitil. It's said that at th e base of a steep climb, he'd shift his bidon from it's holder to his jer sey pocket ... he wanted the bike to be as light as possible for the clim b. !
Bob Hillery Retro Randonneur USAC level 2 coach, 240221 Stratham, NH US