The present study aimed to examine the locomotor exploration of PT infants during the first six months of independent walking experience and, in addition, we investigated how characteristics of infant growth and development (e.g., infant profile, anthropometric measurements, and walking experience) could affect their locomotor exploration. PT and FT infants showed similar locomotor exploration, spending most of their time in standing locomotion and exhibiting similar locomotor behavior. Although bivariate correlations indicated that, as walking experience increased, there was a corresponding increase in time spent in standing locomotion, number of bouts, number of steps, and a decrease in time spent sitting for all infants, regression analyses revealed that these associations were significant only among FT infants. Notably, FT infants exhibited improvements in locomotor exploratory behavior of up to 36% and 56% in terms of number of bouts and steps, respectively. This relationship, however, was not observed in PT infants, suggesting that walking experience alone may not be sufficient to attenuate the effects of prematurity on locomotor exploration. The following results are discussed in detail below.

Infant profiles

PT infants in our sample exhibited delays in the onset of independent walking (chronological age) and had longer hospital stays after birth compared to FT infants. These findings are consistent with the literature, which indicates that motor milestone delays in PT infants are often inversely associated with gestational age and length of hospitalization [4, 16]. Many of the PT infants in this study were enrolled in early intervention programs with multidisciplinary teams during their first year, which may have helped to mitigate some developmental delays and support age-appropriate motor behavior [17]. Additionally, PT infants were more frequently from low- or lower-middle-income families and had lower birth weights [1], characteristics previously linked to an increased risk of developmental delays when compared to FT peers [2, 3, 7]. The APGAR score at 5 min was the only infant profile variable linked to locomotor exploration (fewer bouts and more imbalances); other variables were retained for participant characterization. Missing perinatal data, due to complications, adoptions, or lack of documentation, affected both PT and FT groups and reflects common challenges in pediatric records and parental recall [18].

Locomotor exploration

Contrary to our expectations, there were no differences between PT and FT groups in locomotor exploration behaviors (e.g. walking, bouts, steps, and falls). The only exception was the time spent in the lying-down position, which, despite being statistically significant, represented a minimal portion of the session (less than 3% for PT infants) and is unlikely to be clinically meaningful. This finding contrasts with previous studies, as Hempel [12] reported significant qualitative motor differences between PT and FT children, though his study’s more heterogeneous sample with higher developmental risks may have amplified these differences. Similarly, in an assessment conducted 14 days after PT infants achieved the ability to walk 5 meters independently, Groot, Groot, and Hopkins [13] found qualitative challenges in the walking patterns of these children, classifying them as “near poor” and “poor” due to difficulties with balance and coordination, especially when walking fast, changing direction, stopping, and picking up objects during locomotor exploration.

Besides that, in our study, we observed greater variability in the overall behavior of PT infants and their infant profile, while FT infants had more homogeneous characteristics. One possible explanation may be related to the requirements of the behavioral task. Perhaps the experimental situation was not sufficiently challenging to highlight subtle differences in the locomotor skills of PT infants. In the study by Adolph and colleagues [14], for example, the exploratory environment included a larger room, stairs, cushions, different elevations, and toys, resulting in up to 17.4 falls per hour on average for infants with walking experience. These findings suggest that falls are not necessarily indicators of poor motor control, but part of a natural and adaptive learning process. In our study, we observed that infants showed similar locomotor exploration, spending most of their time in standing locomotion (PT: 24.93%, FT: 35.46%) and exhibiting similar locomotor behaviors (i.e. average PT: 623 steps and 2 falls, FT: 995 steps and 3.27 falls). Interestingly, FT infants also showed a wider range in the number of falls, with some participants falling up to eight times during the session.

In fact, falling is one of several typical outcomes of spontaneous locomotor bouts, alongside stopping or taking steps in place [11]. Rather than reflecting failure, falls can be understood as opportunities for infants to gather information about their bodies, balance, and the environment, helping to refine motor strategies over time. Thus, the presence of falls, particularly when accompanied by varied bouts of movement, can indicate active engagement in exploration and ongoing motor learning, rather than indicate motor impairment.

Walking experience and its role in locomotor exploration

Examining the relationship between locomotor exploration variables and infant profile characteristics of all infants, our results showed that increasing walking experience over the first six months of life may affect how FT infants move and interact with objects in the environment, which is expected for the initial development of independent walking [14, 19]. As a novelty, our study also showed that an increase in walking experience is correlated with a decrease in the time spent in sitting and crawling positions, which have not been considered in other studies focusing on locomotor exploration [10, 14, 15, 19].

However, the fact that PT infants did not show a similar trend despite experiencing the same months of walking seems to be a relevant finding in our study. Positive effects of walking experience on locomotor exploration behavior [14, 15, 19] do not appear to apply to PT infants. As Adolph and Hoch argue [5], motor development is not only embodied, constrained by the current status of the body, but also enabling, as each new motor skill opens opportunities for learning and exploration. For PT infants, the same amount of walking experience may not translate into equivalent exploratory behavior due to differences in how their bodies cope with postural control, balance, and biomechanical constraints. These infants may require not only time to walk, but also qualitatively diverse and adaptive experiences to fully benefit from the developmental opportunities enabled by locomotor practice.

Our findings align with recent literature suggesting that walking experience alone may not be sufficient to enhance exploratory behavior in all infants. Graciosa et al. [20] demonstrated that the emergence of locomotor behaviors is not only tied to developmental status, but also to how FT infants aged 5 to 15 months interact with their environment and parental practices. For PT infants in our study, the combination of altered developmental trajectories and fewer adaptive stimulation opportunities may reduce the functional benefits of walking experience on locomotor exploration.

There is a lack of research on whether there are early differences in gait among PT infants and, in addition, whether they improve with age and more walking experience [4]. To our knowledge, this is the first study to find that the amount of walking experience does not appear to mitigate the effects of prematurity on the locomotor skills used to drive new exploratory experiences. This finding is important since subtle alterations in PT infants may be hard to identify, leading many of them to be excluded from early intervention programs. These programs might compensate for possible motor delays, families’ lack of knowledge about prematurity-related issues, and low-quality parent-child interactions [21]. Furthermore, changes in neuropsychomotor function, coupled with a lack of opportunities to move, may compromise the developmental cascades [22]. Studies have shown that different neural networks are formed in response to the quantity and quality of experiences that infants are exposed to during the first few months of life [23].

Therefore, the investigation of the exploration of non-object-oriented situations has been underexplored in PT infants, despite its importance [24]. We aim to bridge the gap in understanding the walking experience and exploratory behavior in an ecological setting, simulating a scenario similar to a typical family’s daily routine. Based on our regression results and previous evidence, PT infants may follow a different developmental trajectory, with subtle impairments in non-object-oriented exploratory behaviors that could affect reaching, object exploration, and cognition [9, 25].

Important aspects of locomotion such as form (i.e., gaits) and function (i.e., mobility) improve with independent walking experience [26]. The focus on mobility provides a more accurate, inclusive, and rich portrait of infant locomotion than just focusing on gait shape, given that infants are challenged daily to make various motor adjustments during periods of exploration. These motor solutions, in addition to making the world more accessible, depend on moment-to-moment relationships between the body and the environment [26]. Considering the linear regression results, we speculate that despite showing similar characteristics of exploratory walking, the functionality of locomotor exploration seems to be impaired in this population. In this sense, we encourage health professionals and caregivers to pay attention to how premature infants solve locomotor problems, and not just be concerned about whether they present the locomotor milestones expected for the age group.

A limitation of our study was the small sample of infants born prematurely, which presented with a wide range of gestational ages and varying risks for developmental delays. Although we did not systematically assess co-morbidities – such as visual impairments or mild motor dysfunctions which are more frequent in PT infants – using formal clinical screening tools, we did have access to participants’ medical records and parental reports to check for exclusion criteria. Importantly, all participants in our sample were able to walk independently and engage in the task. In addition, we were able to pair PT infants with FT peers, which enabled us to answer the questions we posed in this study.