Relationship between pedal force asymmetry and performance in cycling time trial

It remains unclear if cyclists with better performance have less asymmetry. Therefore, this study aimed at assessing the relationship between cycling time trial performance and bilateral asymmetries in pedal forces.

Ten cyclists/triathletes performed an incremental cycling test to exhaustion to measure maximal oxygen uptake and power output. In a second session, bilateral pedal forces were acquired during a 4-km cycling time trial on the stationary cycle ergometer. Resultant and effective forces were computed along with the index of effectiveness at 500 m sections of the time trial using instrumented pedals. Intra-limb variability and the asymmetry index were calculated for each force variable.

Multivariate analysis assessed bilateral differences in pedal forces accounting for power output, pedalling cadence and oxygen uptake of each cyclist. Force variables did not change throughout the test (effective - P=0.98, resultant - P=0.90 and index of effectiveness - P=0.99) with larger force applied by the dominant limb (11-21%). The relationship between asymmetries and performances was strong for the effective force (r=-0.72) but weak for the resultant force (r = 0.01) and for the index of effectiveness (r=-0.29). Substantial asymmetries were observed for the effective force (36-54%), resultant force (11-21%) and for the index of effectiveness (21-32%) at greater range than intra-limb variability (effective force =8-22%, resultant force =5-10% and index of effectiveness =1-3%).

Larger asymmetries in effective force were related to better performances during the 4-km time trial with low intra-limb variability for force measures suggesting consistence in asymmetries for individual cyclists.