Unstable surface training as a rehabilitation exercise modality improves strength, range of motion, and postural control in young adults with grade 1 ankle sprain

Background: Ankle sprains are one of the most common musculoskeletal injuries in young adults, often leading to chronic ankle instability if inadequately rehabilitated. Restoring range of motion (ROM), strength, and postural balance are critical to prevent recurrence. This study investigated the comparative effects of stable surface training (SST) and unstable surface training (UST) on ankle joint function and balance in individuals with Grade 1 ankle sprains. Methods: Twenty healthy adult males diagnosed with Grade 1 ankle sprains were randomly assigned to SST (n = 10) or UST (n = 10) groups. Participants underwent a 4-week balance training program, three times per week. Pre- and post-intervention assessments included ankle joint ROM (dorsiflexion, plantarflexion, inversion, eversion), isokinetic muscle function, and static and dynamic balance tests (eyes-closed single-leg stance test (ECSLT) and Y-balance test). Results: Both groups showed significant improvements over time in ankle strength and balance (p < 0.05). However, only the UST demonstrated significant increases in dorsiflexion, plantarflexion, and inversion ROM (p < 0.05), as well as in total and average ROM (p < 0.05). While both SST and UST enhanced balance, UST showed a greater tendency for improvement, particularly in dynamic postural control. UST was more effective than SST in improving multidirectional ankle ROM and enhancing postural balance. Conclusions: These findings suggest that proprioceptively challenging rehabilitation protocols should be prioritized in early-stage rehabilitation for Grade 1 ankle sprains to support comprehensive functional recovery. Clinical Trial Registration: This study was registered in the Clinical Research Information Service (CRiS), Republic of Korea, under the registration number KCT0010569 (https://cris.nih.go.kr/cris/search/detailSearch.do?seq=30039&search_page=L).