What is the role of the leg in individuals with Autism Spectrum Disorder (ASD)?

Role of the Leg in Autism Spectrum Disorder

Atypical leg and foot movements during walking serve as potential early markers for ASD identification, while lower limb motor deficits—including proprioception impairments, strength deficits, and coordination problems—contribute to the functional motor challenges seen throughout the lifespan in individuals with ASD.

Leg Movements as Early Diagnostic Markers

Atypical Gait Patterns in Early Development

• Atypical arm and foot movements during walking emerge as potential early markers of ASD during the second year of life, though the exact timing of emergence varies by study design 1.
• Specific gait abnormalities include waddling walk patterns and atypical foot movements that distinguish toddlers with ASD from typically developing children 1.
• These movement atypicalities encompass repetitive actions or posturing of the body, arms, hands, or fingers, including atypical foot movements during walking 1.

Clinical Significance for Early Identification

• Atypical body movements, including leg and foot movements, may emerge as important early markers, though evidence in this domain is less well established than social communication markers 1.
• When atypical leg movements are observed, children should be closely monitored not only for ASD but also for other developmental disorders 1.

Lower Limb Motor Deficits Across the Lifespan

Proprioception Impairments

• Adolescents with ASD demonstrate 1.3-times worse performance during plantarflexion position-based proprioception testing and 2-times worse performance during speed-based proprioception tests compared to neurotypical controls 2.
• These proprioceptive deficits in the lower limbs provide insight into mechanisms underlying reduced coordination and aberrant gait mechanics commonly seen in ASD 2.
• Poor integration of sensory information for efficient motor planning represents a core deficit affecting lower limb function 3.

Strength Deficits

• Individuals with ASD exhibit a 40% reduction in ankle plantarflexion strength compared to neurotypical controls 2.
• Both gross and fine motor performance deficits are present across the entire spectrum of children with ASD, regardless of IQ scores 4.

Coordination and Motor Control Problems

• Children with ASD demonstrate lower gross motor scores on standardized assessments like the Bruininks-Oseretsky Test of Motor Proficiency 4.
• Greater movement variability and lower movement rates characterize lower limb motor performance in ASD 4.
• Motor coordination deficits differ qualitatively from those seen in developmental coordination disorder, with ASD showing specific failures in anticipating object properties during reaching tasks 5.

Clinical Implications for Assessment

Comprehensive Motor Evaluation Requirements

• Occupational and physical therapy evaluations are essential to evaluate sensory and motor difficulties, including lower limb function 1.
• Motor assessments should be sustained even when difficulties appear to improve, as a variable pattern of improvement and worsening has been observed 1.
• Fine and gross motor skills assessment should be part of the comprehensive evaluation for all individuals with ASD 1.

Integration with Overall ASD Management

• Treatment of lower limb motor abnormalities, including toe walking, should be coordinated with speech-language pathology services and occupational therapy for sensory integration dysfunction 6.
• Motor evaluations and interventions should be included in the standard-of-care for children with ASD 4.

Therapeutic Interventions

Physical and Occupational Therapy

• Physical therapy is key for addressing gross motor challenges and should be sustained throughout development 1.
• Occupational therapy evaluation for sensory integration dysfunction and visuomotor delays should occur concurrently with lower limb motor treatment 6.
• Nearly all individuals with ASD seen in clinical settings have fine and/or gross motor challenges requiring ongoing therapeutic intervention 1.

Behavioral and Educational Approaches

• Teaching chains of motor behaviors using forward or backward chaining with reinforcement for completion allows individuals to experience success in multistep motor tasks 1.
• Visual schedules, planners, timers, and assistive technology can circumvent problems related to organizational weaknesses that affect motor planning 1.

Common Pitfalls to Avoid

• Do not assume motor deficits are secondary or less important than social communication deficits—motor impairments correlate strongly with autism severity and functional outcomes 4.
• Avoid waiting for motor delays to resolve spontaneously; early motor delays within the first 2 years may contribute to social impairments 7.
• Do not apply standard developmental coordination disorder rehabilitation programs to ASD without modification, as the motor deficits differ qualitatively between these conditions 5.

Relationship to Core ASD Features

• Motor performance (fine and gross) correlates significantly with IQ but not with autism severity 4.
• Praxis errors correlate strongly with autism severity rather than IQ, highlighting the autism-specific nature of certain motor planning deficits 4.
• Increased sensorimotor noise and variability in basic motor outputs represent fundamental deficits affecting lower limb function 3.