Does training with PowerCranks™ affect economy of motion, cycling efficiency, oxygen uptake and muscle activation patterns in trained cyclists?
Masters Thesis - Jack Burns
Edith Cowen University
PowerCranks™ are claimed to increase economy of motion and cycling efficiency by reducing the muscular recruitment patterns that contribute to the resistive forces occurring during the recovery phase of the pedal stroke. However, scientific research examining the efficacy of training with PowerCranks™ is lacking. Therefore, the purpose of this study was to determine if five weeks of training with PowerCranks™ improves economy of motion (EOM), gross efficiency (GE), oxygen uptake (Error! Bookmark not defined.V.O2) and muscle activation patterns in trained cyclists. Sixteen trained cyclists were matched and paired into either a PowerCranks™ (PC) or Normal Cranks (NC) training group. Prior to training, all subjects completed a graded exercise test (GXT) using normal bicycle cranks. Additionally, on a separate day the PC group performed a modified GXT using PowerCranks™ and cycled only until the end of the 200W stage (PCT). During the GXT and PCT, FeO2, FeCO2 and V.E were measured to determine EOM, GE and V.O2max. Integrated electromyography (iEMG) was also used to examine selected muscular activation patterns. Subjects then repeated the tests following the completion of training on their assigned cranks. No significant improvements were observed for EOM, GE, V.O2max or iEMG in either the PC or NC group when subjects were cycling with normal cranks during the GXT. Likewise, no significant training effects were observed when PC subjects cycled with PowerCranks™ during the PCT. PC group subjects were significantly less efficient and economical, before and after training when cycling with PowerCranks™ compared to cycling with normal cranks. The results from this study do not support benefits claimed by PowerCranks™, however further research is needed to examine the influence of training with PowerCranks™ on various physiological variables over a more prolonged training duration.
This is really an interesting study. It demonstrates the difficulties that users experience when they first get on the cranks and it demonstrates the improvements that people see in the first weeks as they adapt. The only problem is the study didn't quite last long enough (5 weeks) to demonstrate statistical significance in the changes that were seen but that surely were coming. The changes seen were best demonstrated in table 7, which is reproduced below. The NC(NC) group were the normal crank controls testing on normal cranks. The PC(NC) group was the PowerCranks group testing on normal cranks and the PC(PC) group is the PC group testing on PC's. Note the big drop in efficiency when riding on PC's but as one adapts and improves this is transferred to the testing on normal cranks also.
One problem in his study (other than it didn't last very long) is the drop in efficiency seen in the control group over this time is not well explained. In my view, this study does a good job of confirming the findings of Luttrell despite the fact that statistical significance was not reached. The study is part of a masters thesis by the author and is available as a pdf in two parts. Part 1 Part 2 or from the source.