Endurance markers are related with local neuromuscular response for the intact but not for the ACL reconstructed leg during high intensity running

Aim. It has been demonstrated that the local neuromuscular response during high intensity exercise has a strong relationship with endurance markers. However, a diminished neuromuscular response has been reported for the operated leg in athletes having undergone anterior cruciate ligament reconstruction (ACLR). The purpose of the present study was to examine the relationships between endurance markers and the EMG response during high intensity running in ACLR athletes. Methods. Fourteen ACLR soccer players underwent a GXT test to volitional exhaustion and a 10-min bout of high intensity running. During the 10-min bout, EMG data were recorded at the 3 ^rd and 10 ^th minute from the vastus lateralis bilaterally using a telemetric system. The final EMG levels were expressed as a percentage of the initial values. Pearson moment product correlations were used to assess the relationship between the endurance markers of VO _2max, velocity at lactate threshold (vLT), velocity at 4mM (V ₄) and the final EMG levels. Results. Final EMG levels for the intact leg had a very strong relationship with vLT (r=0.77, P=0.001) and a strong relationship with V ₄ (r=0.68, P=0.008). Final EMG levels for the reconstructed leg had moderate relationship with vLT (r=0.47, P=0.09) and V ₄ (r=0.52, P=0.06). Conclusion. The neuromuscular response of the intact leg during high intensity running shows strong to very strong relationships with endurance markers. Failure of the ACLR leg to present relationships of similar strength may indicate that chronic perturbations modify the ability of the local muscular environment to tolerate sustained high intensity efforts.