Persistent Human Quadriceps Muscle Volume Deficits Following ACL Reconstruction Are Associated With No Detectable...

Area of Science:

• Biomedical Engineering
• Orthopedics
• Muscle Physiology

Background:

• Quadriceps muscle deficits can persist years after anterior cruciate ligament reconstruction (ACLR).
• The molecular mechanisms underlying these persistent deficits are not well understood.
• Investigating hypertrophic signaling pathways post-exercise may reveal insights into muscle recovery.

Purpose of the Study:

• To investigate if persistent muscle deficits following ACLR are linked to impaired hypertrophic signaling pathways after resistance exercise.
• To compare muscle volume, strength, and molecular signaling between ACLR and contralateral legs.

Main Methods:

• Twelve participants (2.6 years post-ACLR) underwent MRI and 1RM testing.
• Resistance exercise (leg press) was performed unilaterally.
• Vastus lateralis muscle biopsies were collected pre- and post-exercise for immunoblotting of mTORC1 pathway proteins.

Main Results:

• ACLR legs showed significant deficits in total knee extensor (7.5%), vastus lateralis (7.7%), and rectus femoris (5.8%) muscle volumes.
• Muscle volume deficits correlated with time since injury, but no strength difference was found between legs.
• Exercise induced changes in mTORC1 signaling proteins, but no between-leg differences were detected.

Conclusions:

• Persistent muscle volume deficits after ACLR decrease over time but are not associated with strength deficits.
• No significant differences in mTORC1 signaling were detected between ACLR and control legs post-exercise.
• Further research is needed to explore signaling at different time points post-ACLR and post-exercise.