Fatigue-related neuromuscular outcomes following ACL reconstruction: a systematic review and meta-analysis
TL;DR
Individuals with ACLR are associated with greater post-fatigue impairments in quadriceps CAR and muscle activation compared with healthy people, and Narrative evidence suggests potential impairments in TTS under fatigue conditions, while quadriceps PT reduction was sensitive in analyses and should be interpreted cautiously.
Abstract
Neuromuscular deficits after anterior cruciate ligament reconstruction (ACLR) are well documented, but fatigue-related changes in neuromuscular performance remain unclear. Evidence synthesis on post-fatigue outcomes such as central activation ratio (CAR), peak torque (PT), rate of torque development (RTD), muscle activation, and time to stability (TTS) is limited. This systematic review and meta-analysis were reported in accordance with the PRISMA 2020. PubMed, Web of Science, Scopus, and Embase were searched to 31 January, 2026. Non-randomized studies comparing ACLR and healthy controls under fatigue were included. Quality was assessed using the Joanna Briggs Institute tools. Random-effects meta-analyses were conducted using standardized mean differences (SMD) and 95% CIs, with heterogeneity and sensitivity analyses performed. Outcomes that could not be quantitatively pooled because of substantial heterogeneity or limited comparable data were synthesized narratively. Seventeen studies ( n = 477 participants; 242 ACLR, 235 controls) were included. Compared with healthy controls, individuals with ACLR demonstrated lower post-fatigue quadriceps CAR (SMD: -0.69, p < 0.001, I² = 30%); muscle activation patterns (SMD: -0.62, p < 0.001, I² = 21%) with moderate-certainty; and PT (SMD: -0.38, p = 0.035, I² = 0%) with low-certainty, whereas no significant differences were found for RTD with low-certainty. Due to the limited number of studies and substantial heterogeneity, TTS outcomes were synthesized narratively and suggested potential impairments following ACLR. Individuals with ACLR are associated with greater post-fatigue impairments in quadriceps CAR and muscle activation compared with healthy people. Narrative evidence also suggests potential impairments in TTS under fatigue conditions, while quadriceps PT reduction was sensitive in analyses and should be interpreted cautiously. No RTD differences were observed. Further studies with complete change-score reporting are needed. CRD420251276036.