Barbara Sargent

Infant exploratory learning: influence on leg joint coordination.

A critical issue in the study of infant development is to identify the processes by which task-specific action emerges from spontaneous movement. Emergent leg action has been studied by providing contingent reinforcement to specific leg movements using an overhead infant-activated mobile, however, there is limited information on the strategies used by infants to support the emergence of task-specific leg action from spontaneous movement. The purpose of this study is to (1) determine the ability of 3 month old infants to learn, through discovery, the contingency between leg action and mobile activation using a virtual threshold, and (2) identify strategies, defined by variance of the end-effectors (feet) and hip-knee joint coordination, used by infants that learned the contingency. Fourteen 3 month old infants participated in 2 sessions of mobile reinforcement on consecutive days. As a group, infants increased the percentage of mobile activation to meet performance criteria on Day 2, but did not meet memory or learning criteria across days. However, five infants learned the contingency based on individual learning criteria. When interacting with the mobile on Day 2 as compared to spontaneous kicking on Day 1, infants who learned the contingency, but not infants who did not learn the contingency, increased variance of the end-effectors (feet) in the vertical, task-specific direction and demonstrated less in-phase hip-knee joint coordination. An important discovery is that infants can discover this very specific contingency, suggesting that this movement behavior (action) can be shaped in future work. This may have implications for the rehabilitation of infants with atypical leg action.

Cross-cultural validity of standardized motor development screening and assessment tools: a systematic review

To investigate whether standardized motor development screening and assessment tools that are used to evaluate motor abilities of children aged 0 to 2 years are valid in cultures other than those in which the normative sample was established.

Development of infant leg coordination: Exploiting passive torques

Leg joint coordination systematically changes over the first months of life, yet there is minimal data on the underlying change in muscle torques that might account for this change in coordination. The purpose of this study is to investigate the contribution of torque changes to early changes in leg joint coordination. Kicking actions were analyzed of 10 full-term infants between 6 and 15-weeks of age using three-dimensional kinematics and kinetics. We found 11 of 15 joint angle pairs demonstrated a change from more in-phase intralimb coordination at 6-weeks to less in-phase coordination at 15-weeks. Although the magnitude of joint torques normalized to the mass of the leg remained relatively consistent, we noted more complex patterns of torque component contribution across ages. By focusing on the change in torques associated with hip-knee joint coordination, we found that less in-phase hip-knee joint coordination at 15-weeks was associated with decreased influence of knee muscle torque and increased influence of knee gravitational and motion-dependent torques, supporting that infants coordinate hip muscle torque with passive knee gravitational and motion-dependent torques to generate kicks with reduced active knee muscle torque. We propose that between 6 and 15-weeks of age less in-phase hip-knee coordination emerges as infants exploit passive dynamics in the coordination of hip and knee motions.

Using Contingent Reinforcement to Augment Muscle Activation After Perinatal Brachial Plexus Injury: A Pilot Study

ABSTRACT Aim: Examine the feasibility of increasing muscle activation with electromyographically (EMG)-triggered musical-video as reinforcement for children with perinatal brachial plexus injury (PBPI). Methods: Six children with PBPI (9.3 ± 6.3 months; 5 female, 1 male) and 13 typically developing (TD) controls (7.8 ± 3.5 months; 4 female, 9 males) participated. The left arm was affected in 5/6 children with PBPI. We recorded the integral (Vs) of biceps activation with surface EMG during two conditions per arm in one session: (1) 100 second (s) baseline without reinforcement and (2) 300 s reinforcement (musical-video triggered to play with biceps activation above threshold [V]). We examined the relation between the mean integral with reinforcement and hand preference. Results: Mean biceps activation significantly increased from baseline in the affected arm of the group with PBPI by the 2nd (p < .008) and 3rd (p < .0004) 100 s intervals of reinforcement. Six of 6 children with PBPI and 12/13 TD controls increased activation in at least one arm. A lower integral was linked with hand preference for the unaffected right side in the PBPI group. Conclusion: This study supports contingent reinforcement as a feasible method to increase muscle activation. Future work will examine training dose and intensity to increase arm function.

Infant Discovery Learning and Lower Extremity Coordination: Influence of Prematurity

ABSTRACT Aims: Preterm infants at increased risk for neurodevelopmental disabilities, including cerebral palsy, demonstrate reduced selective leg joint coordination. Full-term infants demonstrate more selective hip–knee coordination when specific leg actions are reinforced using an overhead infant mobile. The purpose of this pilot study was to determine the ability of preterm infants to: (1) perform and learn through discovery, the contingency between leg action and mobile activation, and (2) demonstrate more selective hip–knee coordination when leg actions are reinforced with mobile activation. Methods: At both 3 and 4-months corrected age, ten infants born very preterm and with very low birth weight participated in 2 sessions of mobile reinforcement on consecutive days. Results: The preterm group at 4-months, but not 3-months, learned the contingency between leg action and mobile activation. Preterm infants at 4-months were separated into those that learned (n = 6) and did not learn (n = 4) the contingency. As a group, preterm infants at 4-months who learned the contingency, did not demonstrate more selective hip–knee coordination when interacting with the mobile on Day 2 as compared to spontaneous kicking on Day 1. Conclusions: Preterm infants, as compared to full-term infants, may have difficulty producing more selective hip–knee coordination during task-specific leg action.

Exercise capacity following pediatric heart transplantation: A systematic review

Pediatric HTs account for 13% of all HTs with >60% of recipients surviving at least 10 years post‐HT. The purpose of this systematic review is to synthesize the literature on exercise capacity of pediatric HT recipients to improve understanding of the mechanisms that may explain the decreased exercise capacity. Six databases were searched for studies that compared the exercise capacity of HT recipients ≤21 years old with a control group or normative data. Sixteen studies were included. Pediatric HT recipients, as compared to controls or normative data, exhibit significantly higher resting HR, and at peak exercise exhibit significantly decreased HR, VO2, power, work, minute ventilation, and exercise duration. Peak VO2 appears to improve within the first 2.5 years post‐HT; peak work remains constant; and there is inconclusive evidence that peak HR, HR recovery, and HR reserve improve with time since HT. These results are discussed in the context of the mechanisms that may explain the impaired exercise capacity of pediatric HT recipients, including chronotropic incompetence, graft dysfunction, side effects of immunosuppression therapy, and deconditioning. In addition, the limited literature on rehabilitation after pediatric HT is summarized.

Infant intralimb coordination and torque production: Influence of prematurity

The purpose of this study is to investigate changes in leg joint coordination, intersegmental dynamics, and their relation in infants born preterm (PT) during the first months of life. Kicking actions were analyzed of 11 infants born PT at 6 and 15-weeks corrected age (CA) using three-dimensional kinematics and kinetics; results were compared to the kicking actions of 10 infants born full-term (FT). Both groups changed from a predominately in-phase coordination at 6-weeks CA to a less in-phase coordination at 15-weeks CA, however, at 6-weeks CA, infants born PT demonstrated less in-phase coordination of their ankle joints with their hip and knee joints. Between groups and across ages, both groups demonstrated consistent net and partitioned joint torque profiles, however, at 6-weeks CA infants born PT demonstrated more complex patterns of torque components. In both groups, less in-phase hip-knee coordination was associated with reduced active knee muscle torque and increased passive knee torques, however, passive knee torques had a greater influence on the kicks of infants born PT at 6-weeks CA. At 6-weeks CA, infants born PT, compared to FT, generated kicks with less in-phase hip-knee coordination, hip excursion, hip angular velocity, and hip muscle torque impulse. By 15-weeks CA, differences resolved in all variables except hip muscle torque impulse. These results highlight a different trajectory of leg joint coordination and torque production for infants born PT compared to FT.

Commentary on "Changes in Motor Development During a 4-Year Follow-up on Children With Univentricular Heart Defects".

“How could I apply this information?” Children with hypoplastic left heart syndrome (HLHS) and univentricular hearts (UVH) are delayed in gross motor skills when measured at 1 and 5 years of age. The gross motor skills of these children should be closely monitored by their medical home or, preferably, in a multidisciplinary clinic to ensure that therapeutic intervention is implemented at the appropriate time. As recommended by the American Heart Association, in addition to regular developmental surveillance and screening, children with HLHS and UVH should be formally reevaluated for developmental delay during the critical periods of 12 to 24 months, 3 to 5 years, and 11 to 12 years.1 Parent comments: This study was interesting as we had similar observations in my son. At age 3 years, he was discharged from all therapies because we were told he was doing great. But when he was assessed at a neurodevelopmental cardiac follow-up program at age 5 years, we were told he was delayed. I feel like we lost a few years with respect to his development that we otherwise might not have, if he had been monitored by a physical therapist every 6 months from age 3 years until kindergarten. “What should I be mindful about when applying this information?” This study reported that children with HLHS or UVH and clear abnormalities on magnetic resonance imaging (MRI) were at higher risk for developmental delay when compared with children with normal or mild ischemia on MRI. The terms “mild” and “clear abnormalities” were not defined; thus, clinicians should be cautious when using MRI results to determine the likelihood of developmental delay in this population. Parent comments: It would have been interesting to have a developmental assessment at age 3 years in this study, since that is when early intervention (EI) services end and also when a child with HLHS typically undergoes their Fontan palliation. If all goes well, medical monitoring is less frequent and pre-Fontan activity restrictions are lifted, and there is no longer monitoring by EI therapists. I think we would see a trend of developmental improvement up to age 3 years because of the monitoring and services, followed by a delay at age 5 years.