Early Neuromuscular and Co-activation Patterns After Anterior Cruciate Ligament Reconstruction In Males: A Case-control Exploratory Feasibility Study.
Roberto Ricupito, Marco Bravi, Fabio Santacaterina and 8 others
Two weeks after ACL reconstruction, the operated knee produced about half the quadriceps signal of a healthy knee, and hamstring co-activation was substantially higher across all muscle pairs.
The non-operated knee also showed elevated co-activation.
Key findings
1The operated limb had significantly lower quadriceps activation than healthy controls: VL p < 0.001, VM p < 0.001, BF p = 0.011, while medial hamstring did not differ (p = 0.250).
2Co-activation indices were significantly higher in the operated limb than controls for all four agonist-antagonist pairs (all p < 0.001), with the largest differences in the VM-BF and VM-MH pairs.
3Within the ACLR group, the operated limb showed lower activation than the non-operated limb for all four muscles (VL and VM p < 0.001, BF p = 0.030, MH p = 0.041) and higher co-activation for all pairs.
Still to come
How it was doneWhat they foundWhat it means for PTs
Read the rest of this summary
You get three full summaries a month, free, and we do not ask for a card. Search, the TL;DRs and your library stay unlimited either way.
What it does not show
Fifteen participants per group with no a priori power calculation; the authors call the study hypothesis-generating and note that statistical power may be limited. Males only, so the findings may not apply to female patients, who may show different neuromuscular and co-activation patterns after ACLR. No sEMG normalization was applied, so the raw microvolt values may reflect both genuine differences in neural drive and inter-individual variability in signal amplitude (subcutaneous tissue thickness, electrode-skin impedance). The authors caution that between-group RMS differences should be interpreted with this in mind. Single time point at approximately 15 days; the study cannot say how these patterns evolve over the following weeks or whether they persist. A single isometric task in full extension was used, which does not capture the dynamic, multi-joint control required for walking or sport-specific movements. No direct neurophysiological assessment of arthrogenic muscle inhibition (twitch interpolation, H-reflex, motor unit decomposition), so the mechanistic interpretation of the reduced RMS remains inferential. Single-site convenience sample recruited from one physiotherapy clinic in Rome over a three-month window. Surface EMG is susceptible to cross-talk from adjacent muscles, which may affect the specificity of the recorded signals.
Declared interests
The authors declare that they have no conflicts of interest.
The easy way to misread this
Do not read the raw microvolt values as absolute measures of muscle strength or weakness. No normalization was applied, and the authors state that the differences may reflect both genuine changes in neural drive and inter-individual variability in signal amplitude such as subcutaneous tissue thickness and electrode-skin impedance. In addition, this is a single time point in 15 males, so it describes what the pattern looks like at roughly two weeks post-surgery, not how it recovers or whether it applies to female patients.
Summarised by AI from the full paper, without a clinician reviewing it. Check it against the source before it changes what you do. Read it on PubMed →