Walking In Infants Research Articles

Infant Walking and Everyday Experience: Unraveling the Development of Behavior from Motor Development

Infant Walking and Everyday Experience: Unraveling the Development of Behavior from Motor Development

Effects of 4 weeks of play in standing and walking on gross motor ability and segmental trunk control in preterm infants using a playpen: A randomized control trial

ObjectiveTo investigate the effect of computer-based early intervention with a playpen to enhance standing and walking, and to examine the relationship between changes in gross motor percentile and segmental trunk control in preterm infants nine months corrected age. MethodsForty infants born before 37 weeks of gestation were randomly assigned to either the experimental or control group. The Alberta Infant Motor Scale (AIMS) and the Segmental Assessment of Trunk Control (SATCo) were administered before and after the intervention. The experimental group, consisting of twenty preterm infants, participated in a computer-based early intervention involving 45 min of play in standing and walking positions, five times a week for 4 weeks. ResultsThere were significant between-group differences in the gross motor percentiles of the AIMS (p-value <0.001). In addition, there was a significant difference in all conditions of the SATCo scores (p-value <0.05) compared with baseline score. The change in percentiles of gross motor development was significantly correlated (rs = 0.643; p-value <0.001) with reactive SATCo during walking in infants in the experimental group. ConclusionEarly intervention with a playpen in a standing and walking position can be applied to improve changes in gross motor percentiles and segmental trunk control in preterm infants.

Redesign and ergonomic assessment of a chest-support baby walker.

Parents often use baby walkers (BWs) as assistive devices to improve their infants' independent movement and motor skill acquisition. However, the literature suggests that conventional baby walkers (CBW) may cause delays in an infant's ability to walk independently and musculoskeletal burden on parents. In the current study, a baby walker (RBW) with chest support was redesigned and ergonomically assessed during an infant-walking task. The anthropometric dimensions of 90 infants aged 7-11 months were measured in the city of Urmia, northwestern Iran. Following redesigning based on the results from expert panel meetings and prototyping of the RBW, 18 mothers (age: 28.33±4.27 and height: 163.75±5.32 and weight: 59.45±5.99) with their infants (9 boys and 9 girls) performed a simulated infant walking task in two experimental sessions using the CBW and RBW over a repeated measurements design. The infants' feet track patterns, including the number of steps and step distances were assessed via the image analysis of the footprints. The mothers' body posture and lower back spinal load were evaluated using Rapid Upper Limb Assessment (RULA) technique and 3D Static Strength Prediction Program (3DSSPP), respectively. Wilcoxon signed-rank tests showed infants walked more steps with the RBW (p = 0.002). Similarly, the distance between the infants' left heel strike (p = 0.008) and their right and left toe-off (p = 0.03 and 0.02 respectively) was also significantly lower in the RBW use. Additionally, the body posture of mothers was improved (RULA final score from 7 for CBW to 5 for RBW). Moreover, lower back compression and shear forces were reduced significantly (p = 0.002) by the RBW use. According to the feet track pattern, infants took more balanced steps when the RBW was used. In addition, mothers were subjected to less pressure on the lumbar region when they placed and lifted their infant from the RBW. However, further work is necessary to investigate potential long-term effects of the RBWs use.

Walking and falling: Using robot simulations to model the role of errors in infant walking.

What is the optimal penalty for errors in infant skill learning? Behavioral analyses indicate that errors are frequent but trivial as infants acquire foundational skills. In learning to walk, for example, falling is commonplace but appears to incur only a negligible penalty. Behavioral data, however, cannot reveal whether a low penalty for falling is beneficial for learning to walk. Here, we used a simulated bipedal robot as an embodied model to test the optimal penalty for errors in learning to walk. We trained the robot to walk using 12,500 independent simulations on walking paths produced by infants during free play and systematically varied the penalty for falling-a level of precision, control, and magnitude impossible with real infants. When trained with lower penalties for falling, the robot learned to walk farther and better on familiar, trained paths and better generalized its learning to novel, untrained paths. Indeed, zero penalty for errors led to the best performance for both learning and generalization. Moreover, the beneficial effects of a low penalty were stronger for generalization than for learning. Robot simulations corroborate prior behavioral data and suggest that a low penalty for errors helps infants learn foundational skills (e.g., walking, talking, and social interactions) that require immense flexibility, creativity, and adaptability. RESEARCH HIGHLIGHTS: During infant skill acquisition, errors are commonplace but appear to incur a low penalty; when learning to walk, for example, falls are frequent but trivial. To test the optimal penalty for errors, we trained a simulated robot to walk using real infant paths and systematically manipulated the penalty for falling. Lower penalties in training led to better performance on familiar, trained paths and on novel untrained paths, and zero penalty was most beneficial. Benefits of a low penalty were stronger for untrained than for trained paths, suggesting that discounting errors facilitates acquiring skills that require immense flexibility and generalization.

Developmental Changes of Muscle Synergies in an Infant's Walking.

Primitive stepping is one of the primitive reflexes in newborns in response to external stimuli. It is known that primitive stepping disappears about two months after birth, but its role and the relationship with voluntary gait acquired later are still unknown. In this study, we extracted muscle synergies, spatiotemporal coordination patterns of muscle activities, from EMG measured in one infant during growth (4-18 weeks of age) using non-negative matrix factorization (NMF). We found that a synergy changed before and after the disappearance of the primitive stepping, and others maintained the recruited muscles but changed the onset timing of the activations.

Learning to Move in a Changing Body in a Changing World.

Infants of all species learn to move in the midst of tremendous variability and rapid developmental change. Traditionally, researchers consider variability to be a problem for development and skill acquisition. Here, we argue for a reconsideration of variability in early life, taking a developmental, ecological, systems approach. Using the development of walking in human infants as an example, we argue that the rich, variable experiences of infancy form the foundation for flexible, adaptive behavior in adulthood. From their first steps, infants must cope with changes in their bodies, skills, and environments. Rapid growth spurts and a continually expanding environment of surfaces, elevations, and obstacles alter the biomechanical constraints on balance and locomotion from day to day and moment to moment. Moreover, infants spontaneously generate a variable practice regimen for learning to walk. Self-initiated locomotion during everyday activity consists of immense amounts of variable, time-distributed, error-filled practice. From infants' first steps and continuing unabated over the next year, infants walk in short bursts of activity (not continual steps), follow curved (not straight) paths, and take steps in every direction (not only forward)-all the while, accompanied by frequent falls as infants push their limits (rather than a steady decrease in errors) and explore their environments. Thus, development ensures tremendous variability-some imposed by physical growth, caregivers, and a changing environment outside infants' control, and some self-generated by infants' spontaneous behavior. The end result of such massive variability is a perceptual-motor system adept at change. Thus, infants do not learn fixed facts about their bodies or environments or their level of walking skill. Instead, they learn how to learn-how to gauge possibilities for action, modify ongoing movements, and generate new movements on the fly from step to step. Simply put, variability in early development is a feature, not a bug. It provides a natural training regimen for successfully navigating complex, ever-changing environments throughout the lifespan. Moreover, observations of infants' natural behavior in natural, cluttered environments-rather than eliciting adult-like behaviors under artificial, controlled conditions-yield very different pictures of what infants of any species do and learn. Over-reliance on traditional tasks that artificially constrain variability therefore risks distorting researchers' understanding of the origins of adaptive behavior.

Bidding on the go: Links between walking, social actions, and caregiver responses in infant siblings of children with autism spectrum disorder.

The development of walking is associated with a shift in how neurotypical infants initiate social interactions. Walking infants are more likely to locate objects in distant places, carry them, and then share those objects by approaching caregivers and using gestures to show or offer their discoveries (i.e., moving bids). The simultaneous organization of the behaviors necessary to generate moving bids requires the coordination of multiple skills-walking, fine motor skills, and gesturing. Infants with an elevated likelihood (EL) for autism spectrum disorder (ASD) exhibit differences and delays in each of these behaviors. This study investigated interconnections between infant walking, social actions, and caregiver responses in 18-month-old EL infants with diverse developmental outcomes (ASD, non-ASD language delay, no diagnosis). We observed 85 infant-caregiver dyads at home during everyday activities for 45 minutes and identified all times when infants walked, instances of walking paired with social action (i.e., approaching the caregiver, approaching while carrying an object, producing a moving bid), and whether caregivers responded to their infants' social actions. There were no group differences in infants' production of social actions. Caregiver responses, however, were more clearly modulated by outcome group. While all caregivers were similarly and highly likely to respond to moving bids, caregivers of EL-ASD infants were substantially more likely to respond when their infants simply approached them (with or without an object in hand). Taken together, this research underscores the complexity of EL infant-caregiver interactions and highlights the role that each partner plays in shaping how they unfold.

Infant walking experience is related to the development of selective attention

Previous studies have shown that the way in which infants perceive and explore the world changes as they transition from crawling to walking. Infant walking onset generally precedes advances in cognitive development such as accelerated language growth. However, the underlying mechanism explaining this association between walking experience and cognition is largely unknown. Selective attention is a key factor underlying learning across multiple domains. We propose that the altered visual input that infants obtain as they transition to walking relates to selective attention development and that advances in selective attention may potentially explain previously reported advances in other cognitive domains. As a first step in testing this hypothesis, we investigated how walking experience relates to selective attention. In Study 1, performance of 14-month-old crawlers, novice walkers, and expert walkers was compared on a visual search eye-tracking task (N = 47), including feature and conjunction (effortful) items. Walkers outperformed crawlers on the task in general, and effortful search was enhanced in expert walkers as compared with novice walkers, after controlling for crawling onset and general developmental differences occurring before walking onset. In Study 2, earlier walking onset was related to better visual search performance in 2-year-olds (N = 913). The association appeared to be due to the difference between the 10% latest walkers and the early/average walkers. Taken together, the results of these studies show that walking experience relates to advances in selective attention. This association shows a specific timing in development; it is mainly seen relatively close to the age of walking onset.

Can early physical therapy positively affect the onset of independent walking in infants with Down syndrome? A retrospective cohort study.

The development of both gross and fine motor skills in a child with Down syndrome is generally delayed. The most seriously affected stage is the achievement of independent walking ability, which influences the onset of all following motor and cognitive skills. The study objectives were: 1) to assess the time taken to achieve independent walking ability in a cohort of children with Down syndrome; 2) to examine differences in walking onset by patient characteristics; and 3) to verify the effect of early physical therapy (neurodevelopmental treatment based on Bobath Concept practiced within the first months of life) in the achievement of that skill. A retrospective study was carried out on a cohort of 86 children with Down Syndrome. The knowledge of the exact age of walking onset and information about comorbidities and rehabilitation practiced since birth were the eligibility criteria. The average age at which walking began in the sample was 26 months (standard deviation=9.66). Some patient characteristics proved to be related negatively to the walking onset: gender male, trisomy 21, improved joint ligamentous laxity. When practiced, early physical therapy was able to contrast the delay in walking. NDT-Bobath is a well-known and valid instrument for a child with Down syndrome to attain his highest possible psychomotor functioning level. This study pointed out for the first time ever its capability to contrast the delay on walking onset, which can influence positively the development of the following motor and cognitive skills.

Cascades in action: How the transition to walking shapes caregiver communication during everyday interactions.

New motor skills supply infants with new possibilities for action and have consequences for development in unexpected places. For example, the transition from crawling to walking is accompanied by gains in other abilities-better ways to move, see the world, and engage in social interactions (e.g., Adolph & Tamis-LeMonda, 2014). Do the developmental changes associated with walking extend to the communicative behaviors of caregivers? Thirty infants (14 boys, 16 girls; 93% White, not Hispanic or Latino) and their caregivers (84% held a college degree or higher) were observed during everyday activities at home during the two-month window surrounding the onset of walking (M infant age = 11.98 months, range = 8.74-14.86). Using a cross-domain coding system, we tracked change in the rates of co-occurrence between infants' locomotor actions and caregivers' concurrent language and gesture input. We examined these relations on two timescales-across developmental time, as infants transitioned from crawling to walking, and in real time based on moment-to-moment differences in infant posture. A consistent pattern of results emerged: compared to crawling, bouts of infant walking were more likely to co-occur with caregiver language and gestures that either requested or described movement or provided information about objects. An effect of infants' real-time behavior was also discovered, such that infants were more likely to hear language from their caregivers when they moved while upright compared to prone. Taken together, findings suggest that the emergence of walking reorganizes the infant-caregiver dyad and sets in motion a developmental cascade that shapes the communication caregivers provide. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Longitudinal study of foot pressures during real-world walking as infants develop from new to confident walkers

BackgroundOnset of walking in infants leads to regular cyclic loading of the plantar foot surface for the first time. This is a critical period for evolving motor skills and foot structure and function. Plantar pressure literature typically studies gait only once walking is established and under conditions that artificially constrain the walking direction and bouts compared to how infants move in the real-world. We therefore do not know how the foot is loaded when self-directed walking is first achieved and whether it changes as walking is practiced.Research questionHow do pressures on the plantar foot in real-world walking change from new to confident walking?MethodsFifty-seven infants participated in a two-site longitudinal study. Bespoke child-friendly spaces incorporated large pressure platforms and video. Data was collected at two milestones: new (403 days) and confident (481 days) walking. Steps were defined as walking straight or turning medially/laterally. Pressure variables were calculated for eight-foot regions and compared between milestones.ResultsConfident walking resulted in more steps (median: 18 v 35) and almost twice as many turning steps. During straight-line steps, confident walking increased peak pressures in the medial heel (median: 99.3 v 106.7kPa, p < .05) and lateral forefoot (median: 53.9 v 65.3kPa, p < .001) and reduced medial toe pressure (median: 98.1 v 80.0kPa, p < .05). Relative medial midfoot contact area reduced (median: 12.4 v 11.2%, p < .05) as absolute foot contact increased. A faster transition across stance and a reduced relative contact time in the forefoot were recorded in confident walking.SignificancePressures change rapidly as walking is initiated with significant differences in foot loading evident within an average 77 days. Importantly, these changes differ in straight and turning walking. Continued reliance on assessment of straight-line walking during early stages of ambulation likely fails to characterise 26% of steps experienced by infant feet.

Practice and proficiency: Factors that facilitate infant walking skill.

Infant walking skill improves with practice-crudely estimated by elapsed time since walk onset. However, despite the robust relation between elapsed time (months walking) and skill, practice is likely constrained and facilitated by infants' home environments, sociodemographic influences, and spontaneous activity. Individual pathways are tremendously diverse in the timing of walk onset and the trajectory of improvement, and presumably, in the amount and type of practice. So, what factors affect the development of walking skill? We examined the role of months walking, walk onset age, spontaneous locomotor activity, body dimensions, and environmental factors on the development of walking skill in two sociodemographically distinct samples (ns = 38 and 44) of 13-, 15-, and 19-month-old infants. Months walking best predicted how well infants walked, but environmental factors and spontaneous activity explained additional variance in walking skill. Specifically, less crowded homes, a larger percentage of time in spontaneous walking, and a smaller percentage of short walking bouts predicted more mature walking. Walk onset age differed by sample but did not affect walking skill. Findings indicate that elapsed time since walk onset remains a robust predictor of walking skill, but environmental factors and spontaneous activity also contribute to infants' practice, thereby affecting walking skill.

Diversity and regularity in infant crawling with typical development.

[Purpose] The purpose of this longitudinal study was to investigate the diversity in infant crawling and examine the quantitative regularity in crawling variations necessary for the acquisition of walking in infants with typical development. [Participants and Methods] Infants with no neurological or orthopedic problems participated in this study. Using Internet Protocol (IP) cameras, crawling was simultaneously filmed from six different angles. Filming was continued until the acquisition of independent walking. The crawling movement in the video was coded. We considered the number of different completed codes as the number of variations and examined the cumulative number during the filming period in each participant. [Results] Nineteen infants completed the study. The pattern of change in the cumulative number of variations with increasing age (in days) varied between cases. Although the cumulative number of crawling variations at the time of acquisition of independent walking was inconsistent, it was negatively correlated with the crawling start age (in days). [Conclusion] Diversity exists in infant crawling. Infants who start crawling at a younger age tend to express more variation, whereas infants who start crawling when older tend to express less variation.

Variety Wins: Soccer-Playing Robots and Infant Walking.

Although both infancy and artificial intelligence (AI) researchers are interested in developing systems that produce adaptive, functional behavior, the two disciplines rarely capitalize on their complementary expertise. Here, we used soccer-playing robots to test a central question about the development of infant walking. During natural activity, infants' locomotor paths are immensely varied. They walk along curved, multi-directional paths with frequent starts and stops. Is the variability observed in spontaneous infant walking a “feature” or a “bug?” In other words, is variability beneficial for functional walking performance? To address this question, we trained soccer-playing robots on walking paths generated by infants during free play and tested them in simulated games of “RoboCup.” In Tournament 1, we compared the functional performance of a simulated robot soccer team trained on infants' natural paths with teams trained on less varied, geometric paths—straight lines, circles, and squares. Across 1,000 head-to-head simulated soccer matches, the infant-trained team consistently beat all teams trained with less varied walking paths. In Tournament 2, we compared teams trained on different clusters of infant walking paths. The team trained with the most varied combination of path shape, step direction, number of steps, and number of starts and stops outperformed teams trained with less varied paths. This evidence indicates that variety is a crucial feature supporting functional walking performance. More generally, we propose that robotics provides a fruitful avenue for testing hypotheses about infant development; reciprocally, observations of infant behavior may inform research on artificial intelligence.

Can early physical therapy positively affect the onset of independent walking in infants with Down syndrome? A retrospective cohort study

The development of both gross and fine motor skills in a child with Down syndrome is generally delayed. The most seriously affected stage is the achievement of independent walking ability, which influences the onset of all following motor and cognitive skills. The study objectives were: 1) to assess the time taken to achieve independent walking ability in a cohort of children with Down syndrome; 2) to examine differences in walking onset by patient characteristics; and 3) to verify the effect of early physical therapy (neurodevelopmental treatment based on Bobath Concept practiced within the first months of life) in the achievement of that skill. A retrospective study was carried out on a cohort of 86 children with Down Syndrome. The knowledge of the exact age of walking onset and information about comorbidities and rehabilitation practiced since birth were the eligibility criteria. The average age at which walking began in the sample was 26 months (standard deviation=9.66). Some patient characteristics proved to be related negatively to the walking onset: gender male, trisomy 21, improved joint ligamentous laxity. When practiced, early physical therapy was able to contrast the delay in walking. NDT-Bobath is a well-known and valid instrument for a child with Down syndrome to attain his highest possible psychomotor functioning level. This study pointed out for the first time ever its capability to contrast the delay on walking onset, which can influence positively the development of the following motor and cognitive skills.

The cost of simplifying complex developmental phenomena: a new perspective on learning to walk.

Researchers can study complex developmental phenomena with all the inherent noise and complexity or simplify behaviors to hone in on the essential aspects of a phenomenon. We used the development of walking as a model system to compare the costs and benefits of simplifying a complex, noisy behavior. Traditionally, researchers simplify infant walking by recording gait measures as infants take continuous, forward steps along straight paths. Here, we compared the traditional straight-path task with spontaneous walking during 20 minutes of free play in 97 infants (10.75-19.99 months of age). We recorded infants' footfalls on an instrumented floor to calculate gait measures in the straight-path and free-play tasks. In addition, we scored videos for other critical aspects of spontaneous walking-steps per bout, shape of walking path, and step direction. Studying infant walking during free play incurred no cost compared with the straight-path task, but considerable benefits. Straight-path gait was highly correlated with spontaneous gait and both sets of measures improved with walking age, validating use of the straight-path task as an index of development. However, a large proportion of free-play bouts were too short to permit standard gait measures, and most bouts were curved with omnidirectional steps. The high prevalence of these "non-canonical" bouts was constant over development. We propose that a focus on spontaneous walking, the phenomenon we ostensibly wish to explain, yields important insights into the problems infants solve while learning to walk. Other areas of developmental research may also benefit from retaining the complexity of complex phenomena.

Variability in foot contact patterns in independent walking in infants

The purpose of this work was to quantify plantar pressures and contact areas (and variability thereof) in natural independent walking in infants.

Power in methods: language to infants in structured and naturalistic contexts.

Methods can powerfully affect conclusions about infant experiences and learning. Data from naturalistic observations may paint a very different picture of learning and development from those based on structured tasks, as illustrated in studies of infant walking, object permanence, intention understanding, and so forth. Using language as a model system, we compared the speech of 40 mothers to their 13-month-old infants during structured play and naturalistic home routines. The contrasting methods yielded unique portrayals of infant language experiences, while simultaneously underscoring cross-situational correspondence at an individual level. Infants experienced substantially more total words and different words per minute during structured play than they did during naturalistic routines. Language input during structured play was consistently dense from minute to minute, whereas language during naturalistic routines showed striking fluctuations interspersed with silence. Despite these differences, infants' language experiences during structured play mirrored the peak language interactions infants experienced during naturalistic routines, and correlations between language inputs in the two conditions were strong. The implications of developmental methods for documenting the nature of experiences and individual differences are discussed.

Infant Social Development across the Transition from Crawling to Walking.

The onset of walking is a developmental transition that sets in motion a cascade of change across a range of domains, including social interactions and language learning. However, research on the unfolding of such change in the infant across this transition is limited. This investigation utilized a longitudinal design to examine the effect of walking acquisition on infant social development and parent perceptions of the infant to explore how changes in these factors relate with infant language development. Parents reported on infant social behaviors and their perception of the infant, as well as motor and language development, in 2-week intervals from 10.5 to 13 months of age. Mixed linear models revealed infant initiation of joint engagement (e.g., pointing, bringing objects to the parent) and following of the parent's joint engagement cues (e.g., point following, gaze following) increased as a function of infant walking experience, particularly between 2- and 4-weeks after the onset of walking, independent of age. Additionally, the parent's perception of the infant as an individual increased between 2- and 4-weeks after the infant began to walk. Finally, the unique relations of infant walking experience, following of social cues, and the parents' perception of the infant as an individual with infant language development were examined. Infant following of joint engagement behaviors and parent perception of the infant as an individual were related to receptive, but not productive, vocabulary size. Additionally, infant walking experience remained a significant predictor of infant receptive and productive language. These findings provide insight on important factors that change as the infant begins to walk. Future research utilizing more direct assessment of these factors is described, as well as general patterning of developmental change across the transition from crawling to walking.

Gait Transitions in Human Infants: Coping with Extremes of Treadmill Speed.

Spinal pattern generators in quadrupedal animals can coordinate different forms of locomotion, like trotting or galloping, by altering coordination between the limbs (interlimb coordination). In the human system, infants have been used to study the subcortical control of gait, since the cerebral cortex and corticospinal tract are immature early in life. Like other animals, human infants can modify interlimb coordination to jump or step. Do human infants possess functional neuronal circuitry necessary to modify coordination within a limb (intralimb coordination) in order to generate distinct forms of alternating bipedal gait, such as walking and running? We monitored twenty-eight infants (7–12 months) stepping on a treadmill at speeds ranging between 0.06–2.36 m/s, and seventeen adults (22–47 years) walking or running at speeds spanning the walk-to-run transition. Six of the adults were tested with body weight support to mimic the conditions of infant stepping. We found that infants could accommodate a wide range of speeds by altering stride length and frequency, similar to adults. Moreover, as the treadmill speed increased, we observed periods of flight during which neither foot was in ground contact in infants and in adults. However, while adults modified other aspects of intralimb coordination and the mechanics of progression to transition to a running gait, infants did not make comparable changes. The lack of evidence for distinct walking and running patterns in infants suggests that the expression of different functional, alternating gait patterns in humans may require neuromuscular maturation and a period of learning post-independent walking.