Neuromechanical response to passive cyclic loading of the ACL in non-professional soccer players: A pilot study

To investigate the effects of passive cyclic loading (CYC) on anterior tibial translation (ATT), knee extensor and flexor muscle strength and activation in soccer players.

Cross-sectional study.

Functional Assessment Laboratory; Participants: Eight healthy competitive soccer players.

The knee of the dominant limb was subjected to 10 min of CYC at 200 N force.

ATT was measured before and after CYC. Percentage of variation was used to estimate ACL creep. Knee extension and flexion maximal voluntary contractions (MVCs) were assessed both before and after CYC. EMG amplitudes of both Biceps Femoris (BF) and Vastus Lateralis (VL) were recorded during both MVCs and CYC.

There was a 20.7% increase in ATT after CYC application (p<0.001). Post-CYC agonist and antagonist BF activations were 37.7% and 18.4% lower than pre-CYC ones during MVCs (p<0.05). BF EMG activity in the last 30s of CYC was 19.9% higher than in the first 30s (p<0.05).

The increased ATT and the variations in neuromuscular activation of the BF in response to loading may expose the knee at higher injury risk by increasing joint instability. Further studies are required to thoroughly investigate these aspects in both laboratory and real-field settings.