The impact of errors in infant development: Falling like a baby

Utilization of recommended safe-landing strategies during falls in mountain biking

Falls are common in mountain biking (MTB), and often involve high speeds, large descent heights, and rough landing terrains. However, most falls in MTB do not cause serious injury. This may be due, in part, to protective movements used by MTB riders to avoid injury. Such "safe-landing strategies" are commonly discussed in the MTB community. However, studies have not synthesized or examined the validity of the recommended strategies. Our goal in this study was to determine whether riders utilize recommended safe-landing strategies during real-life falls in MTB. To address this goal, we identified 11 recommended safe-landing strategies through online content analysis and experienced MTB rider surveys. We then analyzed videos of 300 real-life MTB falls using a structured questionnaire to determine whether riders utilized the recommended strategies. The most commonly used strategies were upper limb bracing (58.3 %), elbow flexion at landing (48.0 %), stepping (47.0 %), knee flexion at landing (43.0 %), and bike separation (40.0 %). The least utilized strategies were reach-to-grasp (4.7 %), use of the arms to shield the face (6.3 %) and dismounting from the bike (6.7 %). Moderately utilized strategies included body rolling (26.7 %), neck rotation (26.7 %), and tucking (18.3 %). In 96 % of falls, rider utilized at least 1 recommended landing strategy. On average, riders utilized 3.04 (SD 1.6) recommended landing strategies when falling. Our results indicate that falls in MTB elicit common movement strategies that align with recommended techniques for avoiding injury during falls. Future research should examine the role of exercise in enhancing safe-landing responses and preventing injuries in MTB.

An update of the development of motor behavior

This primer describes research on the development of motor behavior. We focus on infancy when basic action systems are acquired-posture, locomotion, manual actions, and facial actions-and we adopt a developmental systems perspective to understand the causes and consequences of developmental change. Experience facilitates improvements in motor behavior and infants accumulate immense amounts of varied everyday experience with all the basic action systems. At every point in development, perception guides behavior by providing feedback about the results of just prior movements and information about what to do next. Across development, new motor behaviors provide new inputs for perception. Thus, motor development opens up new opportunities for acquiring knowledge and acting on the world, instigating cascades of developmental changes in perceptual, cognitive, and social domains. This article is categorized under: Cognitive Biology > Cognitive Development Psychology > Motor Skill and Performance Neuroscience > Development.

The development of gait and mobility: Form and function in infant locomotion

The development of locomotion can be described by its form (i.e., gait) and its function (i.e., mobility). Both aspects of locomotion improve with experience. Traditional treatises on infant locomotion focus on form by describing an orderly progression of postural and locomotor milestones en route to characteristic patterns of crawling and walking gait. We provide a traditional treatment of gait by describing developmental antecedents of and improvements in characteristic gait patterns, but we highlight important misconceptions inherent in the notion of "milestones". Most critically, we argue that the prevailing focus on gait and milestones fails to capture the true essence of locomotion-functional mobility to engage with the world. Thus, we also describe the development of mobility, including the use of mobility aids for support and propulsion. We illustrate how infants find individual solutions for mobility and how the ability to move cascades into other domains of development. Finally, we show how an integration of gait and mobility provides insights into the psychological processes that make locomotion functional. This article is categorized under: Psychology > Motor Skill and Performance Psychology > Development and Aging.

Natural-ish behavior: The interplay of culture and context in shaping motor behavior in infancy

What is natural behavior and how does it differ from laboratory-based behavior? The "natural" in natural behavior implies the everyday, complex, ever-changing, yet predictable environment in which children grow up. "Behavior" is motor action and is foundational to psychology, as it includes all things to function in everyday environments. Is behavior demonstrated in the laboratory un-natural? Suppose behavior emerges spontaneously, in a context that is most common to the animal but an observer is there to document it using particular research tools. Is that behavior natural or natural-ish? Methods can powerfully affect conclusions about infant experiences and learning. In the lab, tasks are typically narrowly constrained where infants and children have little opportunity to display the variety of behaviors in their repertoire. Data from naturalistic observations may paint a very different picture of learning and development from those based on structured tasks, exposing striking variability in the environment and behavior and new relations between the organism and its environment. Using motor development as a model system, in this chapter we compare frameworks, methods, and findings originating in the lab and in the field, applied and adapted in different settings. Specifically, we recount our journey of pursuing the study of cultural influences on motor development in Tajikistan, and the challenges, surprises, and lessons learned.

Variations in infants' physical and social environments shape spontaneous locomotion

Independent locomotion is associated with a range of positive developmental outcomes, but unlike cognitive, linguistic, and social skills, acquiring motor skills requires infants to generate their own input for learning. We tested factors that shape infants' spontaneous locomotion by observing forty 12- to 22-month-olds (19 girls, 21 boys) during free play. Infants were recruited from the New York City area, and caregivers reported that 25 infants were White, six were Asian, four were Black, and five had multiple races; four were Hispanic or Latino. All infants played in four conditions: two environmental conditions (gross-motor toys, fine-motor toys) crossed with two social conditions (alone, together with a caregiver). Infants moved more in the gross-motor toy conditions than in the fine-motor toy conditions. However, the effect of playing with a caregiver differed by toy condition. In the gross-motor toy conditions, playing with a caregiver did not affect how much infants moved, but in the fine-motor toy conditions, playing with a caregiver further depressed infant locomotion. Infants with more walking experience moved more with gross-motor toys but not with fine-motor toys. Differences in the amount of locomotion between conditions were related to how infants used toys and the interactions between infants and caregivers. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

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.

Pitfall or pratfall? Behavioral differences in infant learning from falling

Researchers routinely infer learning and other unobservable psychological functions based on observable behavior. But what behavioral changes constitute evidence of learning? The standard approach is to infer learning based on a single behavior across individuals, including assumptions about the direction and magnitude of change (e.g., everyone should avoid falling repeatedly on a treacherous obstacle). Here we illustrate the benefits of an alternative "multiexpression, relativist, agnostic, individualized" approach. We assessed infant learning from falling based on multiple behaviors relative to each individual's baseline, agnostic about the direction and magnitude of behavioral change. We tested infants longitudinally (10.5-15 months of age) over the transition from crawling to walking. At each session, infants were repeatedly encouraged to crawl or walk over a fall-inducing foam pit interspersed with no-fall baseline trials on a rigid platform. Our approach revealed two learning profiles. Like adults in previous work, "pit-avoid" infants consistently avoided falling. In contrast, "pit-go" infants fell repeatedly across trials and sessions. However, individualized comparisons to baseline across multiple locomotor, exploratory, and social-emotional behaviors showed that pit-go infants also learned at every session. But they treated falling as an unimpactful "pratfall" rather than an aversive "pitfall." Pit-avoid infants displayed enhanced learning across sessions and partial transfer of learning from crawling to walking, whereas pit-go infants displayed neither. Thus, reliance on a predetermined, "one-size-fits-all" behavioral expression of a psychological function can obscure different behavioral profiles and lead to erroneous inferences. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Impact forces in backward falls: Subject-specific video-based rigid body simulation of backward falls

A critical missing component in the study of real-world falls is the ability to accurately determine impact forces resulting from the fall. Subject-specific rigid body dynamic (RBD) models calibrated to video captured falls can quantify impact forces and provide additional insights into injury risk factors. RBD models were developed based on five backward falls captured on surveillance video in long-term care facilities in British Columbia, Canada. Model joint stiffness and initial velocities were calibrated to match the kinematics of the fall and contact forces were calculated. The effect of joint stiffnesses (neck, lumbar spine, hip, and knee joint) on head contact forces were determined by modifying the calibrated stiffness values ±25%. Fall duration, fall trajectories, and maximum velocities showed a close match between fall events and simulations. The maximum value of pelvic velocity difference between Kinovea (an open-source software 2D digitization software) and Madymo multibody modeling was found to be 6% ± 21.58%. Our results demonstrate that neck and hip stiffness values have a non-significant yet large effect on head contact force (t(3) = 1, p = 0.387 and t(3) = 2, p = 0.138), while lower effects were observed for knee stiffness, and the effect of lumbar spine stiffness was negligible. The subject-specific fall simulations constructed from real world video captured falls allow for direct quantification of force outcomes of falls and may have applications in improving the assessment of fall-induced injury risks and injury prevention methods.

Integrating Motor Variability Evaluation Into Movement System Assessment

Common assessment tools for determining therapeutic success in rehabilitation typically focus on task-based outcomes. Task-based outcomes provide some understanding of the individual's functional ability and motor recovery; however, these clinical outcomes may have limited translation to a patient's functional ability in the real world. Limitations arise because (1) the focus on task-based outcome assessment often disregards the complexity of motor behavior, including motor variability, and (2) mobility in highly variable real-world environments requires movement adaptability that is made possible by motor variability. This Perspective argues that incorporating motor variability measures that reflect movement adaptability into routine clinical assessment would enable therapists to better evaluate progress toward optimal and safe real-world mobility. The challenges and opportunities associated with incorporating variability-based assessment of pathological movements are also discussed. This Perspective also indicates that the field of rehabilitation needs to leverage technology to advance the understanding of motor variability and its impact on an individual's ability to optimize movement.

IMPACT

This Perspective contends that traditional therapeutic assessments do not adequately evaluate the ability of individuals to adapt their movements to the challenges faced when negotiating the dynamic environments encountered during daily life. Assessment of motor variability derived during movement execution can address this issue and provide better insight into a patient's movement stability and maneuverability in the real world. Creating such a shift in motor system assessment would advance understanding of rehabilitative approaches to motor system recovery and intervention.

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.

Protective responses of older adults for avoiding injury during falls: evidence from video capture of real-life falls in long-term care

BACKGROUND

falls are common in older adults, and any fall from standing height onto a rigid surface has the potential to cause a serious brain injury or bone fracture. Safe strategies for falling in humans have traditionally been difficult to study.

OBJECTIVE

to determine whether specific 'safe landing' strategies (body rotation during descent, and upper limb bracing) separate injurious and non-injurious falls in seniors.

DESIGN

observational cohort study.

SETTING

two long-term care homes in Vancouver BC.

METHODS

videos of 2,388 falls experienced by 658 participants (mean age 84.0 years; SD 8.1) were analysed with a structured questionnaire. General estimating equations were used to examine how safe landing strategies associated with documented injuries.

RESULTS

injuries occurred in 38% of falls, and 4% of falls caused injuries treated in hospitals. 32% of injuries were to the head. Rotation during descent was common and protective against injury. In 43% of falls initially directed forward, participants rotated to land sideways, which reduced their odds for head injury 2-fold. Upper limb bracing was used in 58% of falls, but rather than protective, bracing was associated with an increased odds for injury, possibly because it occurred more often in the demanding scenario of forward landings.

CONCLUSIONS

the risk for injury during falls in long-term care was reduced by rotation during descent, but not by upper limb bracing. Our results expand our understanding of human postural responses to falls, and point towards novel strategies to prevent fall-related injuries.

ON Time Mobility: Advocating for Mobility Equity

Mobility is a human right. The traditional definition of mobility in physical therapy practice is centered on translocation and, while accurate, is not comprehensive. In this article, we propose the ON Time Mobility framework: that all children have the right to be mobile throughout their development to explore, engage in relationships, and develop agency to cocreate their lives. This perspective highlights interconnected principles of timing, urgency, multimodal, frequency, and sociability to begin discussions on supporting the right to hours of active mobility each day for all children. We propose critical evaluation and discussion of these principles followed by a call to action to shift our conceptualization and enactment of mobility. This mobility rights perspective challenges current medical systems, industry, and government to collaborate with children with disabilities, their families and communities to support mobility as a source of physical and social interactions that define and develop individuals (see Supplemental Digital Content 1, the Video Abstract, available at: http://links.lww.com/PPT/A398 ).

Accuracy of Kinovea software in estimating body segment movements during falls captured on standard video: Effects of fall direction, camera perspective and video calibration technique

Falls are a major cause of unintentional injuries. Understanding the movements of the body during falls is important to the design of fall prevention and management strategies, including exercise programs, mobility aids, fall detectors, protective gear, and safer environments. Video footage of real-life falls is increasingly available, and may be used with digitization software to extract kinematic features of falls. We examined the validity of this approach by conducting laboratory falling experiments, and comparing linear and angular positions and velocities measured from 3D motion capture to estimates from Kinovea 2D digitization software based on standard surveillance video (30 Hz, 640x480 pixels). We also examined how Kinovea accuracy depended on fall direction, camera angle, filtering cut-off frequency, and calibration technique. For a camera oriented perpendicular to the plane of the fall (90 degrees), Kinovea position data filtered at 10 Hz, and video calibration using a 2D grid, mean root mean square errors were 0.050 m or 9% of the signal amplitude and 0.22 m/s (7%) for vertical position and velocity, and 0.035 m (6%) and 0.16 m/s (7%) for horizontal position and velocity. Errors in angular measures averaged over 2-fold higher in sideways than forward or backward falls, due to out-of-plane movement of the knees and elbows. Errors in horizontal velocity were 2.5-fold higher for a 30 than 90 degree camera angle, and 1.6-fold higher for calibration using participants’ height (1D) instead of a 2D grid. When compared to 10 Hz, filtering at 3 Hz caused velocity errors to increase 1.4-fold. Our results demonstrate that Kinovea can be applied to 30 Hz video to measure linear positions and velocities to within 9% accuracy. Lower accuracy was observed for angular kinematics of the upper and lower limb in sideways falls, and for horizontal measures from 30 degree cameras or 1D height-based calibration.

(Hyper)active Data Curation: A Video Case Study from Behavioral Science

Video data are uniquely suited for research reuse and for documenting research methods and findings. However, curation of video data is a serious hurdle for researchers in the social and behavioral sciences, where behavioral video data are obtained session by session and data sharing is not the norm. To eliminate the onerous burden of post hoc curation at the time of publication (or later), we describe best practices in active data curation-where data are curated and uploaded immediately after each data collection to allow instantaneous sharing with one button press at any time. Indeed, we recommend that researchers adopt "hyperactive" data curation where they openly share every step of their research process. The necessary infrastructure and tools are provided by Databrary-a secure, web-based data library designed for active curation and sharing of personally identifiable video data and associated metadata. We provide a case study of hyperactive curation of video data from the Play and Learning Across a Year (PLAY) project, where dozens of researchers developed a common protocol to collect, annotate, and actively curate video data of infants and mothers during natural activity in their homes at research sites across North America. PLAY relies on scalable standardized workflows to facilitate collaborative research, assure data quality, and prepare the corpus for sharing and reuse throughout the entire research process.

Making the process of strategy choice visible: Inhibition and motor demands impact preschoolers' real-time problem solving

To examine the real-time process of strategy choice and execution and the role of inhibition in problem solving, 4- to 6-year-old children were asked to navigate a ball around a maze board under high- and low-precision motor demands. Employing a motor problem-solving task made normally hidden cognitive processes observable. Sequential analysis revealed two subtypes of inhibition (response and attentional) that are involved in problem solving and different developmental trajectories for each. Cognition-action trade-offs due to motor and inhibition demands adversely impacted children's strategy choices, but contributed to heightened variability of strategies. Children used fewer strategies with age, reflecting more efficient problem solving due to increasing inhibitory control. When solutions required precision, preschoolers were more likely to have difficulty inhibiting irrelevant and distracting strategies and maintaining appropriate strategies. By preschool age, executive functioning serves to make strategic motor control possible. A video abstract of this article can be viewed at https://www.youtube.com/watch?v=TCLxK7dvheE.