An investigation of asymmetries in cycling: methods and performance implications

Advancements in power meter technology have increased the availability of affordable, userfriendly power meters, resulting in a prevalence in their use amongst cyclists of all performance levels. Power meters present an array of live data, including cycling asymmetry metrics. Although cycling is a bilateral sport with no obvious lateral preference, asymmetries have been observed in uninjured cyclists, typically ranging between 5 to 20%. Contradictory findings within the literature can be attributed to the heterogenous methodologies in this field in relation to measuring, analysing and interpreting kinetic pedalling metrics. We critically evaluated the current methods to determine a best practice for assessing bilateral asymmetries during cycling and identified further investigations required to inform the methodological recommendations for this field, including assessing the measurement error of asymmetries during cycling. Comparing the torque measured by left and right Garmin Vector power pedals (GVPs) against a criterion measure during static load testing, we found that the GVPs were reliable and valid. By conducting a multiple visit study, we showed that the magnitude and direction of asymmetries during cycling are highly variable. An earlier review noted that cyclists exhibit higher asymmetries during low to moderate intensity exercise, whilst bilateral contributions at maximal intensities were suggested to be symmetrical. We revisited this research questions, using our methodological recommendations and benefiting from advancements in technology, and found no clear and consistent effect of intensity on the magnitude of asymmetry during cycling. Interestingly, asymmetries were negatively associated with gross efficiency, a key determinant of cycling performance. Greater resistive forces generated by the limb contributing least to net power could have resulted in the ipsilateral limb generating greater ii power to overcome the additional resistance, which could explain the increased oxygen cost of cycling with larger asymmetries. Further work is needed to understand the effect of technique on asymmetries in cycling.