1. The Effect of Exercise on Neuromuscular Performance Post-ACL Tear

2. What does the ACL do? Joint stabilization Prevents Neural organ
anterior translation of tibia
excessive internal rotation of tibia
knee hyperextension
Neural organ

3. Mechanism of Injury Quick deceleration Hyperextension Rotation
Majority of tears involve zero contact with another person
“act of God”

4. Arthrogenic Muscle Inhibition (AMI)
likely helping to prevent painful and potentially detrimental movements
Treatement  TENS to allow for more motoneurons to be recruited during the voluntary contraction promoting more complete restoration of strength
The inability to completely activate a muscle
Potential factor contributing to quadriceps weakness
Reduced motor drive to muscles surrounding a joint as a possible protection mechanism
Occurs bilaterally

5. Mechanisms of AMI
Mechanoreceptors in ACL deliver sensory information to the spinal cord
joint movement, joint loading, and joint position
After rupture, less excitability of the quadriceps muscles and therefore atrophy
Posted with permission

6. Figure 1.Palmieri-Smith and Thomas’ proposed neural pathway for arthogenic muscle inhibition in the anterior cruciate ligament.

7. Figure 2. Konishi et al.’s proposed neural pathway for arthrogenic muscle inhibition in the anterior cruciate ligament.

8. Figure 3. Reduction of arthrogenic muscle inhibition over time.

9. Treatment Active contractions with TENS/EMS
Typical rehab exercises for ACL tears include: lunges, squats, hamstring curls, step ups, single leg bodyweight deadlifts
Used in conjunction with TENS/EMS can help activate muscle fibres during these exercises
Eccentric contractions have been shown to lessen muscle atrophy

10. Eccentric contractions
Lepley et al.
4 groups, NMES, NMES and E, E, standard protocol without NMES or E
NMES and E, and E > NMES alone and standard protocol
Eccentric exercises were eccentric repetitions on leg press (4x10, 2 min rest between sets)
Intensity was 60% eccentric 1RM

11. Eccentric contractions choose type II muscle fibre types
It is thought that these fibers are inhibited post-surgery
Eccentric contractions promote activation of these fibres resulting in greater force production

12. Implications for Future Rehab Procedures
Adding eccentric contractions with neuromuscular stimulation could help reduce arthrogenic muscle inhibition

13. References
American Orthopaedic Society for Sports Medicine. (March 2014). Anterior Cruciate Ligament (ACL) Injuries. Retrieved from Konishi, Y., Fukubayashi, T., & Takeshita D. (2002). Mechanism of quadriceps femoris muscle weakness in patients with anterior cruciate ligament reconstruction. Scandinavian Journal Medicine Science Sports, 12, Lepley, L. K., Wojtys, E. M., & Palmieri-Smith, R. M. (2015). Combination of eccentric exercise and neuromuscular electrical stimulation to improve quadriceps function post-ACL reconstruction. The Knee, 22, Padua, D. A. (2015, April 13). Influence of Vibratory Stimuli on Neuromuscular Function. Retrieved from Palmieri-Smith, R. M. & Thomas, A. C. (2009). A neuromuscular mechanism of posttraumatic osteoarthritis associated with ACL injury. Exercise Sports Science Review, 37,