Triceps Surae Neuromuscular Activity During Single-leg Jumping Tasks in Individuals After Anterior Cruciate Ligament Reconstruction.
Florian Forelli, Ayrton Moiroux-Sahraoui, Jean Mazeas and 3 others
At about six months post-ACLR, soleus activation during single-leg jumps was significantly lower than in healthy controls, even in athletes who had met return-to-running criteria.
The operated and non-operated legs showed no difference from each other.
Key findings
1Soleus EMG activity was significantly lower in the ACLR group than in controls during both the counter-movement jump and the drop jump.
2Gastrocnemius medialis activity was significantly lower in the ACLR group during the drop jump but not during the counter-movement jump; gastrocnemius lateralis did not differ significantly in either task.
3No significant differences were found between the operated and non-operated limbs within the ACLR group for any of the three muscles in either task.
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What it does not show
Very small sample (12 vs 9) with no a priori power calculation; the authors themselves call the findings preliminary and note that non-significant results (gastrocnemius lateralis, between-limb) may reflect insufficient power rather than a true absence of difference. No concurrent measures of plantarflexor strength, jump height, ground-reaction forces, or joint kinetics were collected, so it is impossible to tell whether the lower EMG reflects lower force, a different movement strategy, or simply a different activation pattern. EMG amplitude does not directly reflect muscle force; the authors state this explicitly and note the EMG–force relationship is influenced by multiple physiological and methodological factors. Single centre, three surgeons, and a narrow postoperative window (mean 5.6 months) limit generalisability; two participants also had a meniscal repair, which may have altered early rehabilitation. Analysis was restricted to the propulsion phase of the counter-movement jump and a fixed 0.5-second window before peak in the drop jump; the full motor pattern and timing of activation were not examined. It is not possible to determine whether the observed activation differences were present before the injury or are a consequence of surgery and rehabilitation.
Declared interests
The authors declare no conflicts of interest.
The easy way to misread this
Do not read the lower soleus and gastrocnemius medialis EMG as proof that these patients have weaker ankles, impaired landing mechanics, or a higher risk of re-injury. The paper collected no force, ground-reaction, or jump-performance data, and the authors state plainly that EMG amplitude does not directly reflect muscle force production. With only 12 and 9 participants, the non-significant findings (gastrocnemius lateralis, between-limb) may simply be underpowered rather than truly absent.
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