Handgrip Strength, Trunk Muscle Endurance, and Functional Mobility in Adolescents With Mild Intellectual Disability

Study Design

This was a comparative, cross-sectional observational study. Participants were not assigned to any treatment, exercise program, or other intervention. All assessments were completed during a single study visit, and no 8-week intervention or follow-up assessment was conducted.

Participants

The study included 51 adolescents aged 12-18 years. The mild intellectual disability group consisted of 24 adolescents with a clinical diagnosis of mild intellectual disability according to DSM-5 criteria. The comparison group consisted of 27 typically developing adolescents without a diagnosis of intellectual disability, neurodevelopmental disorder, neurological disease, orthopedic condition, or serious systemic disease affecting assessment performance.

Assessments

Handgrip strength was measured separately for the right and left hands using a digital hand dynamometer. Three trials were performed for each hand, and the mean of the three trials was recorded in kilograms.

Trunk muscle endurance was assessed using the McGill trunk endurance test battery, including the trunk flexor endurance test, trunk extensor endurance test, right side bridge test, and left side bridge test. Performance duration was recorded in seconds.

Functional mobility was assessed using the Timed Up and Go Test and the Timed Up and Down Stairs Test. Completion times were recorded in seconds, with shorter times indicating better functional mobility.

Study Objective

The primary objective was to compare handgrip strength, trunk muscle endurance, and functional mobility between adolescents with mild intellectual disability and typically developing peers. The study also examined the relationships among these variables.

Registry Clarification

The initial registry version contained outcome-measure labels and assessment time points that did not correspond to the final assessment battery. After study completion, the record was updated to reflect the actual enrollment, the single-visit assessment schedule, and the outcome measures that were administered. Previous versions of the registry record remain accessible through the record history.

Inclusion criteria

• Adolescents aged 12-18 years.
• For the mild intellectual disability group: a clinical diagnosis of mild intellectual disability according to DSM-5 criteria.
• Ability to understand and follow simple verbal instructions.
• Ability to complete the assessment procedures safely.
• For the typically developing group: no diagnosis of intellectual disability, neurodevelopmental disorder, neurological disease, orthopedic condition, or serious systemic disease that could affect assessment performance.
• Written informed consent obtained from the participant's legal guardian.
• For participants with mild intellectual disability, verbal assent obtained using an age- and cognition-appropriate explanation.

Exclusion criteria

• An orthopedic or neurological limitation preventing completion of the assessments.
• An additional medical or comorbid condition that could substantially affect assessment performance.
• Inability or unwillingness to complete the assessment session.