Background and Purpose: The purpose of this article is to describe single-case studies and contrast them with case studies and randomized clinical trials. We highlight current research designs, analysis techniques, and quality appraisal tools relevant for single-case rehabilitation research. Summary of Key Points: Single-case studies can provide a viable alternative to large group studies such as randomized clinical trials. Single-case studies involve repeated measures and manipulation of an independent variable. They can be designed to have strong internal validity for assessing causal relationships between interventions and outcomes, as well as external validity for generalizability of results, particularly when the study designs incorporate replication, randomization, and multiple participants. Single-case studies should not be confused with case studies/series (ie, case reports), which are reports of clinical management of a patient or a small series of patients. Recommendations for Clinical Practice: When rigorously designed, single-case studies can be particularly useful experimental designs in a variety of situations, such as when research resources are limited, studied conditions have low incidences, or when examining effects of novel or expensive interventions. Readers will be directed to examples from the published literature in which these techniques have been discussed, evaluated for quality, and implemented.

This perspective article provides support for 4 interrelated tenets: grounded perceptual-motor experience within cultural and social contexts forms cognition; exploration through early behaviors, such as object interaction, sitting, and locomotion, broadly facilitates development; infants and children with limited exploration are at risk for global developmental impairments; and early interventions targeting exploratory behaviors may be feasible and effective at advancing a range of abilities across developmental domains and time. These tenets emphasize that through the promotion of early perceptual-motor behaviors, broader, more global developmental advancements can be facilitated and future delays can be minimized across domains for infants and children with special needs. Researchers, educators, and clinicians should build on these tenets to further demonstrate the effectiveness of targeted early interventions. The goals of these interventions should be not only to advance targeted perceptual-motor skills in the moment but also to more broadly advance future abilities and meet the early intervention goal of maximizing children's learning potential.

Objective: Our objective was to evaluate the efficacy of the Sitting Together and Reaching to Play (START-Play) intervention in young infants with neuromotor disorders. Method: This randomized controlled trial compared usual care early intervention (UC-EI) with START-Play plus UC-EI. Analyses included 112 infants with motor delay (55 UC-EI, 57 START-Play) recruited at 7 to 16 months of age across 5 sites. START-Play included twice-weekly home visits with the infant and caregiver for 12 weeks provided by physical therapists trained in the START-Play intervention; UC-EI was not disrupted. Outcome measures were the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley); the Gross Motor Function Measure; reaching frequency; and the Assessment of Problem Solving in Play (APSP). Comparisons for the full group as well as separate comparisons for infants with mild motor delay and infants with significant motor delay were conducted. Piecewise linear mixed modeling estimated short- and long-term effects. Results: For infants with significant motor delay, positive effects of START-Play were observed at 3 months for Bayley cognition, Bayley fine motor, and APSP and at 12 months for Bayley fine motor and reaching frequency outcomes. For infants with mild motor delay, positive effects of START-Play for the Bayley receptive communication outcome were found. For the UC-EI group, the only difference between groups was a positive effect for the APSP outcome, observed at 3 months. Conclusion: START-Play may advance reaching, problem solving, cognitive, and fine motor skills for young infants with significant motor delay over UC-EI in the short term. START-Play in addition to UC-EI may not improve motor/cognitive outcomes for infants with milder motor delays over and above usual care. Impact: Concepts of embodied cognition, applied to early intervention in the START-Play intervention, may serve to advance cognition and motor skills in young infants with significant motor delays over usual care early intervention. Lay Summary: If you have a young infant with significant delays in motor skills, your physical therapist can work with you to develop play opportunities to enhance your child’s problem solving, such as that used in the START-Play intervention, in addition to usual care to help your child advance cognitive and motor skills.