Effects of neuromuscular electrical stimulation combined with blood flow restriction training on lower-leg neuromuscular function in individuals with chronic ankle instability: a randomized controlled trial

Abstract Background Chronic ankle instability (CAI) is characterized by recurrent giving way, impaired function, and persistent neuromuscular deficits. Although neuromuscular electrical stimulation (NMES) and blood flow restriction training (BFRT) have both been proposed as adjunctive rehabilitation strategies, their combined effect in CAI remains unclear. This study examined whether NMES combined with BFRT provides additional benefits beyond exercise alone or isolated modalities in individuals with CAI. Methods In this assessor-blinded, randomized, sham-controlled trial, 60 participants with CAI were randomly allocated to control group (CON, n  = 15), BFRT group ( n  = 15), NMES group ( n  = 15), or BFRT combined with NMES group (CMB, n  = 15). All groups completed an identical 8-week standardized exercise program. The FAAM-Sports subscale was designated as the primary outcome. Secondary outcomes included normalized surface electromyography (sEMG) amplitudes of the tibialis anterior, medial gastrocnemius, and peroneus longus during eyes-closed single-leg standing and unanticipated single-leg landing tasks; peak torque during ankle maximum voluntary isometric contractions (MVICs); the star excursion balance test (SEBT) composite score; and the FAAM-ADL subscale. The data were statistically analyzed via SPSS software, and a p -value  Results Fifty-five participants completed the intervention. Significant Group × Time interactions were observed for normalized sEMG amplitudes of the TA, MG, and PL during both functional tasks; EV, DF, and PF peak torque; SEBT; and both FAAM subscales. Within-group analyses showed increases in all six task-related sEMG measures in the CMB group, compared with five in the NMES group (except PL RMS amplitude during eyes-closed single-leg standing) and one in the BFRT group (MG RMS amplitude during inversion landing). All groups improved in EV, DF, and PF peak torque, SEBT, FAAM-ADL, and FAAM-Sports. At post-intervention, the CMB group had higher PL RMS amplitudes than the other three groups during both tasks and higher EV peak torque and FAAM-ADL scores than all other groups. However, CMB did not differ from NMES in TA or MG RMS amplitude, from BFRT in DF or PF peak torque, or from BFRT in FAAM-Sports. Conclusions Adding NMES and BFRT to an 8-week exercise program was associated with higher post-intervention FAAM-Sports scores than exercise alone and NMES alone, but not BFRT alone. The combined intervention also showed a broader pattern of favourable changes across several secondary outcomes, particularly PL activation amplitude and EV strength. However, its advantage was not consistent across all outcomes. These findings suggest that NMES and BFRT may provide complementary short-term benefits when added to exercise. Trial registration Chinese Clinical Trial Registry, ChiCTR2600120401, registered on 03/13/2026. Prospectively registered.