Pulling up on the pedals through the top of the pedal stroke is a very common technique taught to mountain bikers. They are told that by pulling up with the trail leg they can generate equal tension on the pedals through the entire pedal stroke. Driving down hard with the leg, a.k.a “mashing”, is discouraged and is said to decrease power and efficiency.
However, some recent studies have called that advice into question (Mornieux et al. Int J Sports Med 2008; 29:817-822 & Korff et al. Med Sci Sports Exerc 2007; 39:991-995). Two studies in particular have shown that top level cyclists are not actually applying force to the pedal when pulling the trail leg up and, in fact, the power is coming almost exclusively from the lead leg. However, this does not mean that you do not want to “pull up” with the trail leg.
When looking at a good pedal stroke I keep going back to what a good running stride looks like since both are just ways to power lower body locomotion. I call it Barefoot Pedaling, which is an attempt to restore and apply natural movement to the bike, not actually pedaling without shoes.
When running, you need to flex the thigh with the hip flexors to return the trail leg to the start position so it can drive down hard into the ground to propel you forward. This means that you are pulling up with the trail leg but you are not trying to apply force into the running stride. If you are lazy with this return portion of the running stride you will have a weak overall stride and you will have to work on it, however you never try to add to your forward momentum with the trail leg.
That’s where the difference lies on the bike as well and where the confusion over good advice stems from. There is a HUGE difference between pulling up with the hip flexors to get the trail leg back into position and purposefully applying force into the pedals in an attempt to “add to” to the pedal stroke’s power. Top cyclists are pulling through the top and spinning circles, they are just doing it through a much different mechanism than most riders arrive at when given the same advice.
You don’t want to relax the trail leg and let it create drag on the pedals, which interfere with power being generated by the lead leg. However, when you tell a rider that they want to apply force through the top of the pedal stroke they can accomplish it in a variety of ways that have nothing to do with maintaining a solid core and proper use of the hip flexors. The most common way is to pull up on the pedals by bringing the knees towards the chest using the abs, which will usually place a lot of strain on the lower back.
This is also why riders have trouble switching from clipless pedals to flat pedals, which is indicator of a bad pedal stroke. In fact, one of the studies mentioned earlier showed that top riders apply the same pedal stroke technique regardless of the type of pedal they were on (Mornieux et al. Int J Sports Med 2008; 29:817-822). You can still pull up with the hip flexor to get the trail leg over the top and in position with flat pedals but you can’t apply force into the pedals any more – flat pedals simply highlight which technique you are using.
If you find that your feet fly off the pedals when you try flats then you have developed some bad habits that are being exposed – concentrate on the lead leg drive and focus on pulling the top of your thigh up towards your belly button, not on pulling the pedals up with your feet.
I think that this explains why there is so much confusion when it comes to proper pedaling technique – top riders explain what they “feel”, but what they feel and what drives that feeling are two different things. By focusing on the symptoms of a good pedal stroke we’ve missed the boat on the true cause, which is a focus on the hips and not the feet/ pedals. This will help you restore natural movement to the bike and help you develop a pedal stroke that you can apply to any type of pedals and see better power and efficiency.
The #1 lie is that you want to pull the foot and pedal up – you instead need to focus on pulling the thigh up at the hip. This technique will help you develop a smooth, consistent pedal stroke to flats or clipless pedals.