An Integrated Analysis of Leg Length Differences and the Effect of Correctional Techniques on Stroke Mechanics and Performance Indicators in Competitive Cyclists

Abstract

Leg length discrepancy amongst the general population is relatively common, increasing susceptibility to a range of injuries potentially transferable to endurance cyclists. While the effects of such conditions are widely reported for the general population, little is known regarding a repetitive and constrained activity such as cycling. Therefore, the purpose of this study was to assess pedal mechanical asymmetries of trained cyclists with mild leg length discrepancies and the subsequent effects of compensatory strategies (crank length and cleat wedge) on physiological measures of gross efficiency. Participants completed three 15 min trials at a sub maximal intensity for each condition in a single blind (participants) and balanced order with 15 min recovery between conditions. Torque, vastuslateralis Electromyography (EMG), mechanical angles at the hip, knee and ankle, of both left and right sides were recorded along with expired air analysis and heart rate in order to calculate changes in gross efficiency. The main findings show that participants with 5.4 ± 2.9 mm differences in leg lengths showed small asymmetries in mechanical angles, torque production and muscle activity for which compensatory interventions made positive small changes. Interestingly, these changes resulted in a negative effect on gross efficiency, which would require an adaptation period to remedy any neuromuscular compensatory adaptations. Therefore, cyclists recognized as having leg length discrepancies are recommended to use compensatory interventions such as orthosis, rather than crank length modifications, and that a period of gradual adaptation period be allocated.