Yohan Uhm

Anodal transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has been proposed as an ergogenic aid. Prior reviews pooled heterogeneous outcomes, and none isolated explosive lower-limb power or separated jump output from force–time kinetics. We asked whether anodal M1 tDCS versus sham improves explosive lower-limb power in healthy active adults, analysing these two outcome categories separately. Following PRISMA 2020 (PROSPERO CRD420261438841), four databases were searched up to 3 July 2026 for randomised and crossover trials. Random-effects meta-analyses (REML with Hartung–Knapp) pooled Hedges’ g by category; risk of bias (RoB 2) and certainty (GRADE) were assessed. Seven trials were included. tDCS did not significantly improve jump output (k = 6; g = 0.44, 95% CI −0.05 to 0.92; p = 0.069; I² = 19%). The kinetics estimate was moderate (k = 3; g = 0.67, 95% CI 0.53 to 0.81; I² = 0%) but did not survive a conservative small-sample correction (95% CI −0.23 to 1.57; p = 0.086). Certainty was very low throughout. Including a further trial whose comparator was a no-intervention control made both estimates significant, indicating a fragile evidence base. Current evidence does not establish an ergogenic benefit; adequately powered, pre-registered trials are needed.

Background: Non-contact anterior cruciate ligament (ACL) injury is common and disabling, often requiring reconstruction and predisposing individuals to early post-traumatic osteoarthritis, making scalable, exercise-based prevention a clinical and public health priority. Excessive peak vertical ground reaction force (vGRF) during landing is a modifiable biomechanical risk marker for ACL injury, although whether reducing it lowers injury incidence is unproven. We evaluated the effect of movement retraining on peak vGRF during landing in pivot-sport athletes and general athletic populations. Methods: MEDLINE (PubMed), Embase, and the Cochrane Central Register of Controlled Trials were searched from inception through to 25 May 2026. Two reviewers independently screened records and extracted data. Random-effects meta-analyses (DerSimonian–Laird) used Hedges’ g; risk of bias was assessed with RoB 2 and certainty with GRADE. The protocol was registered in PROSPERO (CRD42025116119). Results: Nine comparisons from eight randomised controlled trials (292 participants) were included. Movement retraining significantly reduced peak vGRF (Hedges’ g = −0.94, 95% CI −1.34 to −0.54; I² = 63%), with larger effects in general athletic populations (g = −1.50) than in pivot-sport athletes (g = −0.66; subgroup difference p = 0.005). Knee flexion angle at initial contact showed a non-significant increasing trend (g = 0.48; p = 0.18). Certainty of evidence (GRADE) was low. Conclusions: Movement retraining was associated with a reduction in peak vGRF during landing, a surrogate biomechanical marker for ACL injury, on the basis of low-certainty evidence with substantial heterogeneity (I² = 63%). A subgroup difference favouring general over pivot-sport athletes was observed but is exploratory, resting on only three general-athletic comparisons. Because no included trial measured injury incidence, whether these biomechanical changes reduce ACL injury is unknown, and the findings should be regarded as hypothesis-generating.