Integrating multi-session transcranial direct current stimulation with routine physical therapy to improve quadriceps strength and activation in athletes during subacute recovery following ACL reconstruction: A double-blind RCT

Abstract

Objective Anterior cruciate ligament reconstruction (ACLR) is often associated with persistent quadriceps weakness and impaired voluntary activation. Integrating active anodal transcranial direct current stimulation (a-tDCS) with routine physical therapy (RPT) may offer additional neuromodulatory benefits during the subacute phase of rehabilitation in nonprofessional male athletes. Methods Twenty male nonprofessional athletes (mean age: 27.50 ± 7.24 years, BMI: 25.83 ± 3.49) were randomly assigned to two groups: active M1 a-tDCS + RPT (n = 10) and sham M1 a-tDCS + RPT (n = 10). Both groups received 10 sessions of a-tDCS during RPT. The active group received 2 mA stimulation for 20 minutes per session, while the sham group received 2 mA for 30 seconds, followed by ramp-down and discontinuation. Quadriceps strength was measured using an isokinetic dynamometer, voluntary activation was assessed using the superimposed burst technique (Central Activation Ration (CAR) method) Baseline measurements were taken after 10 weeks of RPT, prior to the combined intervention phase. Results The active a-tDCS group demonstrated a significant improvement in CAR compared to the sham group (mean difference: 6.85%; 95% CI: 1.92–11.77; p = 0.01), while the sham group showed a slight, non-significant decrease (2.54%; p = 0/80). Within-group analysis revealed significant voluntary activation improvements in the active group (p = 0.005), with no significant changes in the sham group (p = 0.59). No significant between-group differences in quadriceps strength were observed (p = 0.4), although both groups showed significant within-group improvements (active: 21.8%, P ≤ 0.001; sham: 14.8%, p = 0.02), likely due to the effects of RPT. Conclusion The integration of multi-session a-tDCS with RPT during the subacute phase of ACLR recovery significantly enhanced voluntary activation and knee-specific function, as measured by the International Knee Documentation Committee (IKDC) score. These findings suggested that multiple-channel a-tDCS may facilitate neural activation and functional recovery, with clinically meaningful improvements in IKDC scores observed in the active group. Trial Registration: Iranian Registry of Clinical Trials (IRCT) Registration Number: IRCT20231113060048N1; Registered on December 28, 2023. URL: https://irct.behdasht.gov.ir/search/result?query=IRCT20231113060048N1