This was a test that Greg Romero put together....(Warning it is a pretty long read, but worth it)

So I conducted a test with 1 subject: a 17 year old expert. The test was to see if utilizing the "upstroke" with clips vs. focusing on just 100% of the downstroke using clips. The test protocol was of the following: A road bike equipped with an SRM Professional Power Meter with a 15.2 slope with a 322 zero offset. The cranks were 172.5 in length and the gear roll out was approximately 50.5 inches (fairly easy). The sprint protocol was a stand start, clipped in, full out acceleration for 5 full cranks (relative average distance to the first jump of any track). This sprint was done standing up holding the handlebars in the drops.

The subject did a set of 4 sprints focusing on a standard pedal stroke, focusing on the downstroke of the pedal (timing of 1-5 o'clock). The next set was 4 sprints was using the same downstroke with an intention of using the upstroke at 7-11 o'clock. The following numbers are the average of the 2 sets of sprints and the results are as follows:

Focusing on the downstroke only:
1426 Peak Power Watts/ 122.25 RPM/ 19.2 Max Speed/ 987.5 lb. in

Focusing on downstroke and upstroke:
1241 Peak Power Watts/ 108 RPM/ 17.67 Max Speed/ 966 lb. in

Obviously the decision is unanimous across the board in all 4 categories: Trying to use the upstroke to help accelerate the bike is acutally inhibiting overall peak performance of power. The difference was 185 watts of peak power or approximately 13%! That is the difference of about a half a bike length! The speed was a difference of 1.53 MPH! Obviously the cadence (RPM) tells a bigger story of leg speed with a difference of 14.25 RPM! This tells me that implementing the upstroke from the start, to the first jump is a significant disadvantage in Peak power, speed, RPM and torque! I draw the conclusion that focusing on just the downstroke, unassissted by the upstroke is some how neurologically uninhibited and the power of 1 leg doing the work will be just as good as both legs trying to do the same work.

*and just for fun, we put on flat pedals and did the same protocol and those average numbers are:
1165 Peak Power Watts/ 118 RPM/ 18.2 Max Speed 834.3 lb. in

After seeing the Flats pedals out performing the Clips implemented with the upstroke, it gives us a solid
conclusion, no matter what pedal, focus on the hardest straight forward downstroke that you can possibly power! Clips still rule over flats too! Why? Like I had mention before, the clips eliminate the phenomenon of "flat pedal drift" or that the pedal stroke is more stabilized with it being 100% secured to the pedal. The prime movers of the leg muscles producing concentric/eccentric contractions can focus on what it does best without hesitation of trying to keep the ball of the foot attached to the pedal.

I will soon have a set of Shimano Saints equipped with the SRM power meter spider (it's in Germany being engineered right now) and I will put those on Mike Day's bike soon and he will race with it. I'm going to try to get a few more on a few other women/men. I will do the test with the BMX bike soon, but I do feel a sprint standing up regardless of bike is still just that; a sprint. I replicated the gearing and went easier than harder. Now, these numbers could change on a BMX bike, perhaps someone like the OG, who has a PowerTap hub, can conduct the same test. I felt body positioning when I was doing it, or when my subject was doing it, was relatively the same on both separate sets (downstroke only vs. downstroke/upstroke combo). Will it change on a BMX bike? The chances don't look good.

The plan wasn't to prove that clips are producing more power than flats (in which you know that, I don't need to tell you that), but perhaps guys like K Robinson wanted to know about training for clips. I always heard parents and other riders talk about this "upstroke" phenomenon as this is the reason why they're faster. So far my theory is right on track: It's the attachment component (shoe to pedal) that lets the prime movers of the knees (quads/hams) to take a break from stabilizing the foot through the lower leg (which is part of knee flexion). Follow me? This lets the prime movers, again, be uninhibited of the dynamic elastic component of a powering a pedal stroke. The best analogy is this: A free weight squat vs. a smith machine (barbell attached to rails in which you don't have to use stabilizers laterally speaking) squat.

Is this meant to persuade those who prefer flats to cross over? No. It's simply to tell those who choose to use clips, to not focus on the upstroke so much. If you noticed, according to my flat pedal numbers, they are not far behind in speed with the clips (downstroke only). This tells us that kids like Corben Sharrah were not so much at a disadvantage using flats than it's preferred counter part. Simply the talent was taking over. Also, this tells us that kids should start off on flat pedals and learn how to pedal the downstroke powerfully and also fluidly as possible. Maybe then when skills are well developed and they're looking for speed enhancement, the skills will be able to handle the extra speed. So it's in my opinion that kids of any age can very well be competitive and make up the deficit through specific strength training development on the bike doing sprints and also basic body weight bearing exercises (such as the ones in the 8-12 year old programs I offer). I think everyone should use the off season to develop the stabilizers and perhaps even through the preparation and competition season depending on timing of event and tapering for an event. You can even look t using flats as developing power by taking a step back to take 2 steps forward. Again, BMX is a power sprinting sport. The limiting factor to power is also strength. Using flat pedals will call in stabilizers, strengthening them to enable strength of prime movers to aid in power. It's in indirect way. Flat pedals are okay too! Your not a disadvantage so start sprinting, start developing strength in the gym! Get to work and stop looking for the equipment component being the deciding factor to your racing.

Greg Romero