Effects of isolated gastrocnemius tightness on foot posture, strength, function, and balance in children aged 7–16: a case-control study

Abstract

Background: Isolated gastrocnemius tightness (IGT) has been linked to foot conditions, but its clinical relevance in children remains unclear. This study aimed to evaluate foot posture, muscle strength, functional performance, and postural control in children with IGT. Methods: Fourteen children diagnosed with IGT, defined as having passive ankle dorsiflexion < 10° with the knee extended and ≥ 10° with the knee flexed according to the Silfverskiold test, and 14 age-matched children without IGT were included in the study. Foot posture was assessed using the Foot Posture Index (FPI-6), while lower extremity muscle strength was measured with a MicroFET2 handheld dynamometer. Functional performance was evaluated through single-leg and double-leg horizontal jump tests, and postural control was analyzed using the Biodex Balance System (BBS). Results: Children with IGT exhibited significantly poorer foot posture and ankle mobility compared to healthy controls, with very large effect sizes in foot posture index (FPI-6; d = 3.59 right, 3.31 left) and dorsiflexion range (e.g., active dorsiflexion in knee extension: 0.21° vs. 19.14°, d = 3.59). Muscle strength was also lower, particularly in the iliopsoas (right: 8.16 vs. 10.76 kgf, d = -1.24) and gluteus maximus (left: 8.71 vs. 11.42 kgf, d = -1.30). In functional assessments, the IGT group performed worse in horizontal jump tests, with reduced distances in both double-leg (126.10 vs. 142.75 cm, d = -0.50) and single-leg jumps (103.82 vs. 136.00 cm, d = -0.98). BBS data showed impaired postural stability (e.g., overall stability index: 0.76 vs. 0.43, d = 0.90) and lower limits of stability scores, especially in backward (37.79 vs. 66.00, d = -1.27) and diagonal directions (e.g., backward/left: 43.07 vs. 63.50, d = -1.08). Furthermore, sway scores were higher in the IGT group during the sensory organization test, particularly under eyes open/firm surface (0.89 vs. 0.52, d = 1.12) and foam conditions, indicating balance deficits. Conclusions: Children with IGT exhibit notable impairments in foot posture, muscle strength, functional performance, and postural control compared to their healthy peers. These findings underscore the need for further research to confirm the observed associations in children with IGT and may help guide early identification efforts and the development of future intervention strategies aimed at improving functional outcomes. Trial registration: ClinicalTrials.gov ID: NCT06363136 Registration date: 04.09.2024.