Researchers in Western Australia and Victoria have published an original research article in the British Medical Journal Open Sport and Exercise Medicine, investigating quadriceps motor cortex inhibition and facilitation during rehabilitation for patients who have undergone anterior cruciate ligament reconstruction (ACLR).

Following ACLR, maladaptive changes often occur in the motor cortex representation of the quadriceps, evidenced by increases in intracortical inhibition and facilitation.

The primary objective of this proof of concept study was to determine whether anodal transcranial direct current stimulation (tDCS) can alter quadriceps intracortical inhibition and facilitation within an early-ACLR population after six weeks of application during exercise.

The secondary objectives included the evaluation of whether anodal tDCS can alter quadriceps maximal voluntary isometric contraction and hamstring intracortical inhibition and intracortical facilitation in an ACLR population after six weeks of application during exercise (from week 2 post-ACLR).

Twenty-two participants were randomly assigned to either an anodal or sham tDCS group.

The primary motor cortex received either anodal tDCS or sham tDCS for 20 minutes.

This treatment occurred three times per week, for six weeks from week 2 post-ACLR.

Transcranial magnetic stimulation quantified quadriceps short-interval intracortical inhibition, long-interval intracortical inhibition and short-interval intracortical facilitation.

The researchers found significant group-by-time and time effects for short-interval intracortical inhibition and a group-by-time effect for anodal tDCS.

While there were no significant time effects for long- interval intracortical inhibition or short-interval intracortical facilitation, they did observe a significant group-by-time effect for anodal tDCS for short-interval intracortical facilitation.

This study provided proof of the efficacy of anodal tDCS post-ACLR in reducing maladaptive quadriceps inhibition and facilitation.

The researchers demonstrated that anodal tDCS improved facilitation and inhibition post-ACLR, which are drivers of arthrogenic muscle inhibition.

They state that the relationship of primary motor cortex changes to maximal voluntary isometric contraction post-ACLR requires further investigation.

Murphy et al. Anodal transcranial direct current stimulation (tDCS) modulates quadriceps motor cortex inhibition and facilitation during rehabilitation following anterior cruciate ligament (ACL) reconstruction: a triple-blind, randomised controlled proof of concept trial. BMJ Open Sport and Exercise Medicine 2024;10:e002080. doi: 10.1136/bmjsem-2024-002080