Combination of eccentric exercise and neuromuscular electrical stimulation to improve quadriceps function post-ACL reconstruction

•Eccentric exercise restored levels of quadriceps function that were better than NMES.•Eccentrics are attractive alternative to NMES, as it is easily delivered, safe and well-tolerated.•We report preliminary results of therapies that positively influence quadriceps function.•To determine the true clinical effect, larger sample sizes and patient randomization are needed.

BackgroundNeuromuscular electrical stimulation (NMES) has been shown to reduce quadriceps activation failure (QAF), and eccentric exercise has been shown to lessen muscle atrophy post-ACL reconstruction. Given that these are two critical components of quadriceps strength, intervention combining these therapies may be effective at reinstituting quadriceps function post-reconstruction. Thus, the aim of this study was to evaluate the effectiveness of a combined NMES and eccentric exercise intervention to improve the recovery of quadriceps activation and strength post-reconstruction.MethodsThirty-six individuals post-injury were placed into four treatment groups (N&E, NMES and eccentrics; E-only, eccentrics only; N-only, NMES-only; and STND, standard of care) and ten healthy controls participated. N&E and N-only received the NMES protocol 2 × per week for the first 6 weeks post-reconstruction. N&E and E-only received the eccentric exercise protocol 2 × per week beginning 6 weeks post-reconstruction. Quadriceps activation was assessed via the superimposed burst technique and quantified via the central activation ratio. Quadriceps strength was assessed via maximal voluntary isomeric contractions (Nm/kg). Data was gathered on three occasions: pre-operative, 12-weeks-post-surgery and at return-to-play.ResultsNo differences in pre-operative measures existed (P > 0.05). E-only recovered quadriceps activation better than N-only or STND (P < 0.05). N&E and E-only recovered strength better than N-only or the STND (P < 0.05) and had strength values that were similar to healthy at return-to-play (P > 0.05).ConclusionEccentric exercise was capable of restoring levels of quadriceps activation and strength that were similar to those of healthy adults and better than NMES alone.Level of evidence: Level 3, Parallel longitudinal study