Cross-Segmental Transfer Effects of Lower Limb Cross-Training Priming on Upper Extremity Functional Recovery in Pediatric Unilateral Cerebral Palsy: A Randomized Controlled Trial

Abstract

Background: Upper extremity deficits in unilateral cerebral palsy (UCP) severely restrict daily autonomy. Although movement-based priming is known to stimulate neuroplasticity, the distal transfer of lower extremity (LE) training to augment paretic upper limb (UL) function remains largely uninvestigated. This randomized controlled trial evaluated whether a 6-week LE cross-training (CT) priming regimen enhances UL functional restoration in pediatric UCP. Methods: Thirty-six children (6–8 years) were randomized to a conventional physical therapy cohort (n = 18) or an experimental CT cohort (n = 18). The CT group performed high-resistance contractions utilizing the non-paretic LE immediately preceding standard therapy. Blinded evaluations quantified Handgrip Strength (HGS) via dynamometry, grasping proficiency via the Peabody Developmental Motor Scales (PDMS-2), and gross dexterity via the Box and Block Test (BBT) pre and post intervention. Results: Analysis indicated a robust, near-significant between-group effect (Wilks’ Λ = 0.775, p = 0.057). While both cohorts achieved substantial internal improvements, the CT participants displayed superior developmental trajectories across all domains, notably in grasping age equivalence (34.28 ± 6.33 vs. 25.78 ± 3.26 months) and HGS (3.89 ± 0.79 vs. 3.03 ± 0.53 kg). Conclusions: LE cross-training priming may be a feasible adjunct, but it did not demonstrate statistically significant additional UL benefit versus standard rehabilitation in this sample. Therefore, these results should be interpreted as exploratory and hypothesis-generating. This potential cross-segmental transfer may theoretically operate via interhemispheric facilitation, warranting further investigation in larger, adequately powered trials.