Efficacy of different frequencies of extracorporeal shockwave on plantar flexor spasticity of the ankle in patients with stroke: a single-center, prospective, single-blind, randomized controlled trial

Extracorporeal shockwave therapy (ESWT) can effectively relieve post-stroke spasticity; however, research comparing the impact of different ESWT frequencies is limited. In this study, we investigated the therapeutic efficacy of different ESWT frequencies for post-stroke ankle plantar flexor spasticity. In this prospective, single-blind, randomized controlled trial, we recruited patients treated in the Rehabilitation Department of Shenzhen Second People’s Hospital for post-stroke ankle plantar flexor spasticity between January 2024 and September 2024. The participants were randomly assigned to the control (n = 15), 4 Hz ESWT (n = 15), and 10 Hz ESWT (n = 15) groups. All groups received conventional rehabilitation therapy; the 4 Hz and 10 Hz ESWT groups received additional ESWT. The ESWT intervention lasted for 3 weeks, with two interventions per week. ESWT was administered at 2 bar, 4 Hz, and 2000 pulses for the 4 Hz group and 2 bar, 10 Hz, and 2000 pulses for the 10 Hz group. Assessments were conducted before treatment, after the first treatment, and at the end of intervention using the modified Ashworth scale (MAS), passive joint range of motion (PROM), ankle clonus score, medial gastrocnemius muscle oscillation frequency (MGF), lateral gastrocnemius muscle oscillation frequency (LGF), medial gastrocnemius muscle dynamic stiffness (MGS), lateral gastrocnemius muscle dynamic stiffness (LGS), and the Fugl-Meyer assessment of the lower extremity (FMA-LE). Visual analog scale (VAS) tool was used before and after each ESWT session. The 4 Hz and 10 Hz ESWT groups showed significant difference in LGS after a single treatment (P < 0.05). Following 3 weeks of treatment, both ESWT groups exhibited significant improvements in MAS, PROM, MGF, and LGS compared with the control group (P < 0.05). The 4 Hz ESWT group also demonstrated a significant improvement in MGS compared with the control group (P < 0.05), and the 4 Hz and 10 Hz ESWT groups differed significantly in LGS (P < 0.05). We found that only five patients reported mild pain, which resolved rapidly after treatment and rest. Both single and 3-week ESWT treatments safely reduced the severity of ankle plantar flexor spasticity. The results showed the possibility of superiority of 4 Hz intervention to 10 Hz intervention. Trial registration: This study was registered in the Chinese Clinical Trial Registry on 10 January 2024 (registration Number: ChiCTR2400079721), https://www.chictr.org.cn/bin/project/edit?pid=217074.