This single-arm pilot study will assess the feasibility and preliminary effectiveness of an intensive motor skill intervention (HABIT-ILE) combined with functional strength training (FST) in children with SMA who are receiving disease-modifying therapies. Participants will attend one 6-hour HABIT-ILE + FST session each weekend (Saturday or Sunday) for 15 weeks, for a total of 90 hours of training. Feasibility will be evaluated through questionnaires, and effectiveness through standardized motor function assessments.

Spinal Muscular Atrophy (SMA) is a severe neuromuscular disorder marked by the progressive degeneration of alpha motor neurons in the spinal cord and brainstem, resulting in proximal muscle atrophy and weakness. Based on age of onset and the motor function achieved, children were historically categorized into functional groups. However, recent advances leading to the development of disease-modifying therapies (DMTs) have transformed the management of SMA. Outcomes are now primarily determined by the timing of DMT initiation, with early treatment-ideally before symptom onset-showing significant efficacy in improving motor function and survival. Despite these therapeutic breakthroughs, rehabilitation remains a cornerstone of care for children with SMA. Current clinical guidelines emphasize physical activity, muscle strengthening, and stretching. However, few controlled studies have rigorously evaluated these interventions, and even fewer have examined their combined effects with DMTs. This gap underscores the need for innovative, evidence-based rehabilitation strategies that can complement pharmacological treatments and further promote functional outcomes. Hand-Arm Bimanual Intensive Therapy Including Lower Extremities (HABIT-ILE) is an intervention that integrates bimanual coordination with postural control and gross motor training. Grounded in motor skill learning principles, HABIT-ILE delivers high-intensity, structured practice of progressively increased motor difficulty tasks and functional activities, emphasizing voluntary active movement. The approach has demonstrated efficacy in children aged 6 months to 18 years with cerebral palsy (CP), a non-progressive neurodevelopmental disorder caused by early brain injury. Although SMA and CP differ in pathophysiology, both conditions involve motor impairments that may respond to intensive, task-specific motor training. In individuals with SMA, central neuroplastic mechanisms may help compensate for peripheral motor deficits, while targeted motor training could optimize recruitment and efficiency of residual motor units in the muscle. Strength training, in particular, has demonstrated beneficial effects in individuals with SMA, suggesting that emphasizing skill training requiring increasing endurance and progressively increasing the weights of objects participants handled, may be especially advantageous. In this context, augmenting HABIT-ILE with a functional strength training (FST) component tailored to individual goals may further enhance motor outcomes in this population. The aim of this pilot proposal is to evaluate the feasibility and preliminary efficacy of HABIT-ILE + FST in children with SMA receiving DMTs. Children with SMA will attend one 6-hour HABIT-ILE + FST session each weekend (either Saturday or Sunday) for 15 weeks, adding up to a total of 90 hours. It is hypothesized that this intervention will be well tolerated by children, enhance the acquisition of new motor skills, and foster greater functional independence in daily activities.

Inclusion Criteria:

• Diagnosis of SMA
• Able to participate in all pre and post intervention assessments
• Able to understand and speak English
• Able to understand directions (no significant cognitive delay or serious behavioral issues that would limit participation)
• Receiving a stable dose of disease-modifying therapies for at least 6 months prior to enrollment.

Exclusion Criteria:

• Orthopedic surgery within the last year (confound)
• Initiation of any new pharmaceutical treatment during the study period
• Participation in a clinical trial of an investigational therapy