I've been riding on Look Keo pedals for years, am comfortable in any sort of clip-in system. Today, for the first time in a long while, I cycled on a watt bike in the gym using the straps rather than clipping in (somebody had messed with the cleats and I couldn't get into them).
Long story short, I found I liked that I could slide my left foot fore and aft by a couple cms depending on whether I was well forward, upright, or up on the pedals. Due to nerve damage in my left calf I have to compensate a lot through the pedal stroke, and the leeway of foot placement in a given position seemed to make that easier.
I'm wondering if anyone here who can
ride clipless opts not to for any reason.
I spent the last six years cycling using ordinary quill pedals with no clips or straps. No problems with feet slipping off the pedals. No loss of sustainable power.
I used Look Keo before mostly, but also old fashioned clips and straps for commuting before that.
For time trialling or tri I don't think you would see any loss of sustainable power. You might save a bit of weight, as my lightweight shoes and quill pedals weighed less than cycling shoes and cleats with Keo pedals.
You might find this post from Andrew Coggan of interest. http://forum.slowtwitch.com/...t_reply;so=ASC;mh=25
Back in 1988, we examined the physiological and perceptual responses to riding w/ and w/o toe-clips in n=14 cyclists: https://www.academia.edu/...ol_1988_64_2622-2630
As you would predict (given that most people don't actively pull up on the pedals, at least during steady-state cycling), there was no discernable difference between the two conditions (in terms of heart rate, perceived exertion, blood lactate levels, or O2 cost).
27 y later, the good folks at Global Cycling Network have repeated the same experiment (for n=1) and shared the results via this entertaining video: http://velonews.competitor.com/...s-flat-pedals_351535