Comparison of explosive power, balance and muscle morphology in female volleyball players with and without chronic ankle instability

Ankle sprains are among the most common injuries in athletes, accounting for approximately 80% of all athletic injuries. Recurrent ankle sprains often progress to chronic ankle instability (CAI), which can impair athletic performance. Optimal transmission and control of power and movement to distal segments during sport-specific tasks depend on effective control of trunk positioning and movement relative to the pelvis and lower extremities. The aim of this study was to compare the explosive power characteristics, balance, and morphology of muscles of the lower extremity and trunk between volleyball players with and without CAI.

The study involved 40 volleyball athletes who recruited based on the inclusion criteria of the International Ankle Consortium. Dynamic postural control via Y Balance Test, core stability via Sahrmann’s Stability Test, explosive power via countermovement and squat jump tests was assessed. B-mode ultrasonography was used to examine the morphology muscles including the transversus abdominis (TrA), multifidus, vastus lateralis (VL), gastrocnemius muscles and anterior talofibular ligament. Statistical comparisons between groups were performed using the Mann–Whitney U test for non-normally distributed data and the independent samples t-test for normally distributed data. Intra-rater reliability was calculated using intraclass correlation coefficients.

Although the morphological characteristics of all muscles were similar between the CAI group and the control group (p > 0.05), TrA and VL muscle thickness change ratio were higher in control group than CAI group (effect size CAI_TrA:1.83 Control_TrA:2.21; CAI_VL:0.87 Control_VL:1.60). There was no difference between the groups in terms of the explosive power, high jump, core stability, and dynamic balance results (p > 0.05). The intra-rater reliability of ultrasound measurements ranged from moderate to excellent with values of 0.42 to 0.98 for all assessed muscles.

The morphological characteristics of the trunk and lower-extremity muscles involved in explosive power were similar between athletes with and without CAI, and CAI did not affect dynamic balance, explosive power, core stabilization, or jump height results. It is thought that athletes with CAI adapted to morphological characteristics, except for TrA and VL muscle thickness. These findings suggest that athletes with CAI may develop neuromuscular adaptations that preserve functional performance despite chronic instability.

The study is registered at ClinicalTrials.gov (Identifier: NCT05746663; Registration date: 30-01-2023).