Research Report
Population: Pediatric
Susan V Duff, EdD, PT, OT/L, CHT, Associate Professor, Thomas Jefferson University, Department of Physical Therapy susan.duff@jefferson.edu
Barbara Sargent, PT, PhD, PCS, Assistant Professor of Clinical Physical Therapy, University of Southern California, Division of Biokinesiology and Physical Therapy sargent@usc.edu
Jason Kutch, PhD, Assistant Professor, University of Southern California, Division of Biokinesiology and Physical Therapy kutch@usc.edu
Jamie Berggren, OTR/L, Occupational Therapist IV, Children’s Hospital Los Angeles, Division of Pediatric Rehabilitative Medicine JBerggren@chla.usc.edu
Linda Fetters, PT, PhD, FAPTA, Professor and Sykes Family Chair in Pediatric Physical Therapy, Health and Development, University of Southern California, Division of Biokinesiology and Physical Therapy fetters@usc.edu
Keywords: Plasticity, Pediatric, Muscle, Activation
Purpose: Infants with neurological injury such as perinatal brachial plexus injury (PBPI) are at risk for unilateral weakness in specific arm muscles which can lead to prehensile difficulty and arm disuse. One predictor of recovery is the timing of return in biceps brachii muscle function, thus, it is a critical muscle to activate. This study examined whether a contingent reinforcement program increases bicep muscle activation in infants and toddlers with PBPI and if motion data from wrist-based accelerometry and the Almli Test of Handedness are valid measures of arm activity. Materials/Methods: Twelve typically-developing (TD) and 6 children with PBPI less than 2 years of age participated in this two-group cohort feasibility study on two consecutive days. Day 1: arm activity was recorded with wrist-based inertial sensors during the Almli Test. Day 2: children participated in a contingent reinforcement task. The task required activation of the biceps muscle above an individually determined threshold (V) in order to trigger and play a music video. Biceps activation was measured with surface electromyography (sEMG) separately for each arm. The task sequence: 1) 100s baseline condition (video did not play in response to biceps activation); 2) 300s reinforcement condition (video played when biceps activation was above the threshold); and 3) 100s extinction condition (video did not play). The amount (V) and duration (s) of biceps activation (integral [Vs]) above threshold, per arm, was compared across conditions. Results: The children with PBPI significantly increased biceps activation above baseline during the first 100s (p=0.01), second 100s (p=0.007), and third 100s (p=0.002) interval of reinforcement, but not during extinction. The TD group did not demonstrate a significant change (p>0.01) in activation across conditions. Individually, 7/12 TD and 5/6 children with PBPI increased biceps activation to 1.5 times baseline during at least one 100s interval of reinforcement. The interlimb ratios of arm activity (left/right, affected/unaffected) based on accelerometry data, was related yet, not significantly correlated with Almli Test findings (p>0.05). Conclusions: The infants and toddlers with PBPI increased bicep muscle activation when participating in this contingent reinforcement paradigm. Arm activity as measured by both accelerometry and the Almli test are related yet nonequivalent measures. Clinical Relevance: This experimental paradigm was shown to be feasible and has the potential to increase muscle activation in children with PBPI through self-generated feedback. Further research is needed to determine if longer participation in this paradigm promotes a greater capacity for muscle activation necessary to improve prehensile function in this and other populations at-risk for dysfunction. Accelerometry data collected over a longer duration has been found to be an objective measure of arm use in adults, yet warrants further investigation as an outcome measure in young children with unilateral dysfunction. Funding provided by the Section on Pediatrics of the APTA.
Citation:
Duff, Susan V, EdD, PT, OT/L, CHT; Sargent, Barbara , PT, PhD, PCS; Kutch, Jason J, PhD; Berggren, Jamie , OTR/L; Fetters, Linda , PT, PhD, FAPTA. Contingent Reinforcement: Increasing Muscle Activation of Infants and Toddlers With Neurological Injury.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online. https://u.osu.edu/ivstep/poster/abstracts/062_duff-et-al/