Relationship between tip-toe behavior and soleus - gastrocnemius muscle lengths in individuals with autism spectrum disorders

Background: About 20% of individuals with autism spectrum disorders (ASD) showed tip-toe behavior (TTB). This behavior may be related to a decreased ankle joint range of motion (ROM) in dorsiflexion. Physiologically, gastrocnemius (GM) and soleus (SM) muscles influence ankle ROM independently. However, no studies investigated the relationship between the amount of time individuals with ASD spend in TTB and GM and SM muscle lengths. Objective: To evaluate the relationship between three mutually exclusive clinical patterns of TTB i.e., during standing, walking and running (TTB Class 1), or during walking and running (TTB Class 2), or only when running (TTB Class 3), and GM and SM muscle lengths. Methods: Sixty-nine individuals with ASD (average age: 14.1 ± 3.6 years, 56 males) were enrolled. In a clinical setting, SM and GM muscle lengths of both legs were assessed through a manual goniometer. Measurements were performed by two trained assessors blinded to TTB classifications. Results: Individuals with ASD classified as TTB Class 1 demonstrated a shortening of both GM and SM compared with NO-TTB and TTB Class 3 individuals. Conclusions: Our results support the relationship between TTB severity and GM and SM shortening assessed by a decreased ankle joint ROM in dorsiflexion. Further studies are needed to determine the factors associated with TTB and decreased ankle ROM.