Triceps Surae Neuromuscular Activity During Single-leg Jumping Tasks in Individuals After Anterior Cruciate Ligament Reconstruction.

Background: Modifiable risk factors for anterior cruciate ligament (ACL) injury and re-injury have been widely investigated to inform rehabilitation strategies and return-to-sport decision-making. However, less attention has been given to the electromyographic (EMG) activity of the triceps surae after ACL injury and reconstruction. Hypothesis/Purpose: The primary objective of this study was to compare triceps surae EMG activity during single-leg jumping tasks between individuals who had undergone ACLR and healthy controls. The secondary objective was to examine whether any observed neuromuscular differences were present bilaterally within the ACLR group. It was hypothesized that individuals after ACLR would demonstrate lower triceps surae EMG activity compared with healthy controls and that any observed differences would also be present in the non-operated limb. Study Design: Cross-sectional case-control study. Methods: Twelve individuals with ACLR (mean 5.6 ± 0.7 months postoperatively) and nine healthy controls performed four trials of single-leg countermovement jump (SLCMJ) and single-leg drop jump (SLDJ) tasks. Bilateral surface EMG activity of the triceps surae muscles (gastrocnemius medialis, gastrocnemius lateralis, and soleus) was recorded and normalized to maximal voluntary isometric contraction (% MVIC). For the SLCMJ, peak EMG activity during the propulsion phase was analyzed, whereas for the SLDJ, mean EMG activity was computed over a 0.5-second window preceding peak EMG following ground contact. Between-group and between-limb comparisons were performed using independent and paired t-tests (α = 0.05). Results: Compared with controls, individuals after ACLR demonstrated significantly lower soleus EMG activity during both SLCMJ (p < 0.01) and SLDJ (p = 0.02). Gastrocnemius medialis activity was also significantly lower in the ACLR group during the SLDJ (p < 0.01), whereas no significant differences were observed for gastrocnemius lateralis. No statistically significant differences were found between the operated and non-operated limbs within the ACLR group (all p > 0.05). Conclusion: Individuals with ACLR demonstrate lower triceps surae EMG activity during single-leg jumping tasks, particularly for the soleus. These findings suggest the presence of altered neuromuscular patterns that may be bilateral and muscle specific. Level of Evidence: Level 3, cross-sectional case-control study.