Korff, T., Romer, L. M., Mayhew, I., & Martin, J. C. (2007, June). Effect of Pedaling Technique on Mechanical Effectiveness and Efficiency in Cyclists. Medicine & Science in Sports & Exercise, 39(6), 991-995.
The article aims to determine the effects of various pedaling techniques on mechanical and gross efficiency during constant cycling. The study was participated by eight male cyclists whose four pedaling techniques were observed. The cyclists employed the preferred pedaling method, pedaling in circles, pull emphasized during upstroke, and push emphasized during downstroke. Researchers found that mechanical effectiveness is larger, while gross efficiency is lower when the cyclists pull on the pedal during the upstroke method. Moreover, no significant differences were noted in mechanical and gross efficiency during pushing and circling conditions.
Evenness of torque distribution greater during pulling compared to pushing and preferred
During pulling, index of force effectiveness was significantly greater than other conditions. Yet, gross efficiency (power output in relation to oxygen consumption) was significantly less than other conditions. Could this be generalized to highlight the importance of pulling during short bursts of power needs in races? Track cycling, sprinting, attacking, steep hill climbing? The authors allude to this in their conclusion.
During preferred pedaling, circling, and pushing a significant amount of negative torque occurred during the upstroke.
The authors speculate that in steady state cycling, the extensor muscles may be more efficient power producers.
"Interestingly, the preferred pedaling condition did not differ significantly from the pushing or circling condition in terms of mechanical effectiveness or gross efficiency. It is, perhaps, unsurprising that the preferred pedaling technique was metabolically the most efficient (although not significantly different from the circling and pushing conditions), because the participants are likely to have adopted an efficient pedaling style as a result of training and physiology adaptations. More importantly, however, the type of instruction did not influence gross efficiency unless participants were instructed to actively pull up on the pedal. We can speculate that during steady-state cycling, the pedaling technique may not be a major determinant of cycling performance, because a wide range of pedaling techniques results in similar levels of gross efficiency" (p. 994).
PowerCranks are intended to reduce negative torque during the upstroke. Within the context of the data from this study, would developing strength & efficiency in the flexor muscles overcome the inefficiency reported in this study (thus taking advantage of the better torque of the pull up style)? A study just like this should be done with subjects who ride PowerCranks regularly during training.
The authors indicate a limitation of the study is that it does not rule out the possibility a rider may learn a more efficient pedaling style if they are given enough time to adapt to it in training. Longitudinal studies are needed to explore this.
My conclusions from this study is that cyclists should intentionally improve their flexor muscles during training, in order to get the maximum torque benefits of a pull-up pedaling technique. This can be done through overload of the flexor muscles (hamstrings, soleus, hip fexors) through strength training, one leg pedaling, PowerCranks, steep hills works, sprinting, etc. Normal riding should emphasize the efficiency of the downstroke, activating mostly the extensors (quadriceps, calf). Concentration on developing flexors should be done before a race phase of training, and these should be maintained during the race phase with targeted workouts once per week assuming that racing itself will also provide overload on flexors.
This paper also mentioned the effects of gravity.
see reference list for other good articles to read