Interlimb Asymmetry Thresholds that Negatively Affect Change of Direction Performance in Collegiate American Football Players.

Researchers and strength and conditioning practitioners have had an increased interest in the effects of interlimb asymmetries on different aspects of sport performance over the past couple of years. Interlimb asymmetries have been found to negatively affect performance in key performance indicators (KPI) such as jumping, sprinting, and changing directions, within various sports populations. However, there is no consensus about a meaningful threshold at which asymmetries start to negatively affect KPIs or performance. The aim of this study was to investigate a potentially meaningful threshold for three asymmetry metrics (mean peak velocity [mPV], mean peak power [mPP], mean average power [mAP]) that were extracted from the Bulgarian split squat and found to be significantly related to change of direction performance (via L-drill test) within a sample of collegiate American football players. Receiver operating characteristic (ROC) curves were used to identify asymmetry thresholds for all metrics that discriminated between faster and slower performers in the L-drill. Players with asymmetries over 10.65% (mAP), 14.59% (MPP), and 14.96% (mPV) were identified by ROC curves as more likely to be classified as low performers. These findings may be helpful for practitioners interested in screening athletes for interlimb asymmetries that may negatively affect their change of direction performance.