Spinal cord injury (SCI) is a serious disabling condition (Liu J. et al., 2022; Li et al., 2023), often characterized by impairments of sensory, motor and autonomic nerve function. Compared to persons with complete SCI, those with incomplete SCI may gradually experience improvements in lower extremity walking function through targeted rehabilitation (Werner et al., 2021; Shank et al., 2019; Yuan et al., 2019). Reconstructing gait is a primary focus for persons with incomplete SCI undergoing rehabilitation. The process requires a detailed observation of gait patterns, a comprehensive understanding of gait characteristics, the identification of gait abnormalities, and the formulation of targeted corrections to develop scientifically-based walking rehabilitation strategies (Dambreville et al., 2019; Stampacchia et al., 2022; Herrera-Valenzuela et al., 2022; Zörner et al., 2022). Gait analysis is a scientific method that employs bio-mechanical techniques in order to quantitatively assess indicators, including kinematics, spatiotemporal and dynamics parameters during ambulation (Huang et al., 2022). Surface electromyography (sEMG) is considered a valuable indicator of muscle health and function, with its amplitude strongly correlated with strength and recovery. It is employed to assess the activities of multiple muscle groups engaged in complex movement tasks, such as daily activities, gait, or reaching and grasping actions. These methods are widely used in clinical practice and play an important role in gait reconstruction of SCI persons.

Current research on gait in SCI persons often focuses on the analysis of spatiotemporal parameters at varying injury levels and types (Baniasad et al., 2020; Eliseev et al., 2021; Marinho-Buzelli et al., 2019; Balbinot et al., 2021). Gait is influenced by various physiological factors, including age and gender. Researchers have recognized the necessity of considering the impact of age differences on gait in clinical studies. As age increases, walking ability becomes notably diminished compared to younger adults, characterized by decreased stride length, reduced speed, and shortened single stance time (Park et al., 2018; Motti Ader et al., 2021). Epidemiological evidence in 2022 has indicated that age is a risk factor for diseases related to SCI (Stewart et al., 2022). However, reports have not determined whether an intrinsic connection between walking ability and age among persons with incomplete SCI. Additionally, differences remain unclear in the spatiotemporal, kinematic, and dynamic gait characteristics among age groups of SCI persons.

This cross-sectional observational study characterizes gait and muscle activation patterns across age strata in persons with incomplete SCI. We compared spatiotemporal, kinematic, kinetic and electromyographic parameters between persons with incomplete SCI and neurologically intact controls, testing the hypothesis that young SCI persons demonstrated superior gait performance relative to their older counterparts. The overarching aim is to inform targeted rehabilitation strategies and provide a foundation for clinically applicable gait analysis.

According to the inclusion criteria, 30 cases of young, middle aged and elderly SCI persons were included in each category, and the control groups were constituted with young, middle aged and elderly persons without SCI. In accordance with the etiology classification outlined by the International Spinal Cord Injury Core Data set (version 3.0) (Biering-Sørensen et al., 2023), the causes of SCI among 90 persons were categorized as follows: 33 cases of fall (36.7%), 10 cases of transport (11.1%), 13 cases of tumor (benign/malignant) (14.4%), 9 cases of vascular etiology (10%), 6 cases of assault (6.7%), 4 cases of infection (4.4%) and 15 cases of other non-traumatic spinal cord dysfunction (16.7%), including 16 cases of high falling injury (17.8%) and 17 cases of fall down injury (18.9%). Among these, 26 persons had cervical SCI and 64 persons presented with thoracolumbar SCI (Table 1).

Current evidence lacks clear delineation of age-related differences in gait characteristics and muscle activation parameters among individuals with SCI. To address this, we recruited 90 persons with incomplete SCI and 90 age-matched non-SCI controls, stratified by age, and collected spatiotemporal, kinematic, kinetic, and electromyographic data during walking. Contrary to the expectation that young SCI persons would exhibit better walking function, our results demonstrated that young SCI persons had poorer gait performance compared to middle-aged and elderly counterparts. This finding contrasts with prior reports that unaided walkers show greater strength, speed, and lower metabolic cost than those using aids (Truong et al., 2025). In our cohort, the middle-aged and elderly SCI group had a higher usage rate of ankle-foot orthotics, but these groups exhibited better gait ability. Potential confounders such as gender, pain levels, body mass index (Truong et al., 2025), injury etiology, and walking expectations may underlie this discrepancy.

Current clinical guidelines emphasize that preventive and therapeutic strategies for SCI must account for population-specific injury characteristics, with rehabilitation plans tailored to the underlying trauma mechanism (La et al., 2023; Magg et al., 2024). In our cohort, injury etiology differed markedly by age: high-energy events such as falls from height and transportation accidents predominated in younger and middle-aged individuals, whereas low-energy falls were more common among the elderly (Yokota et al., 2024). Low-energy trauma typically induces less severe primary injury and fewer associated complications (Miyakoshi et al., 2021; Giraldo et al., 2021). In contrast, high-energy impacts often produce greater biomechanical disruption, concentrating stress on spinal ligaments and intervertebral discs and elevating risk for multisystem involvement. Consequently, even among individuals with comparable neurological levels, divergent injury mechanisms across age strata may explain observed variations in gait presentation.

Reduced gait velocity is a key predictor of lower extremity motor and balance function following neurological impairment. In individuals with SCI, disrupted neural drive compromises muscle activation amplitude and inter-muscular coordination. This deficit particularly weakens the hip extensors, hip flexors, and ankle plantar flexors, muscle groups critical for the stance-to-swing transition, thereby directly contributing to slowed walking (Lee et al., 2020). To maintain dynamic stability and ensure controlled forward progression of the center of mass, persons with SCI prolong their stance phase duration relative to able-bodied individuals. The marked differences in velocity and double support time observed between young persons with and without SCI reflect this significant functional decline (Gueugnon et al., 2019), which manifests clinically as muscle weakness, slowed movement initiation, and ambulation capacity loss (Kitamura et al., 2021). Although young persons with SCI often possess a higher premorbid functional baseline, recovery of walking after high-energy trauma is typically protracted. In contrast, elderly individuals with similar-severity, low-energy injuries may face a shorter gap between their post-injury capacity and lower pre-injury expectations. We therefore hypothesize that the non-linear relationship between age and walking ability after incomplete SCI may be partly explained by a discrepant alignment between actual function and walking expectations across age groups, with younger persons confronting a larger perceived functional gap.

Reduced extensibility of the muscle-tendon unit impairs movement control during gait, often manifesting as excessive hip and knee flexion in stance. To regain high-quality walking, younger individuals with SCI demonstrate a greater need for extensor muscle strength during stance compared to their elderly counterparts. This altered strategy increases energy absorption at the knee, while simultaneously reducing the contribution of ankle plantar flexors in swing (Gollie, 2018). To compensate for this distal weakness, proximal overuse of the hip extensors frequently occurs (Nadeau et al., 2011). Furthermore, an anteriorly displaced center of mass promotes a cautious shortening of stride length to mitigate fall risk (Haddas et al., 2018). Such gait deviations are reinforced by muscle-level biomechanical alterations, including excessive co-activation of antagonist muscles, which is a recognized contributor to gait and postural dysfunction in SCI. Collectively, these adaptations reflect a compensatory “stepping strategy” employed to offset diminished limb loading capacity and the loss of a swing phase (Wouda et al., 2024).

Beyond muscle weakness, restrictions in velocity and rhythm following incomplete SCI also stem from reduced joint range of motion. Limitations in hip, knee, and ankle mobility induce progressive physiological and mechanical alterations within the joints. Concurrent declines in motor and sensory function further reshape the kinematic trajectory of movement (Shin, 2022). Together, these factors represent genuine gait-limiting constraints and reflect age-dependent adaptations in neuromuscular control. Notably, during the swing phase, the overall knee flexion angle demonstrated a narrowing trend that correlated positively with age. Although reciprocal gait remained possible, altered flexion-extension amplitudes at the hip, knee, and ankle were apparent. This pattern suggests a compensatory strategy wherein increased flexion at the hip and knee is used to augment joint excursion, thereby promoting enhanced stability and balance during limb advancement.

While sex has been identified as a modest correlate of walking speed, with males typically walking faster (Truong et al., 2025), our study maintained strict inclusion/exclusion criteria that balanced key baseline characteristics like BMI. Nevertheless, an imbalanced gender ratio across age groups, a consequence of recruitment time constraints, may have influenced walking ability comparisons. Additionally, although participants completed four familiarization walks at a natural pace, the attachment of sensors and inertial measurement units to the lower limbs introduced a potential constraint. The inherent foreign body sensation and heightened caution likely prevented a fully natural walking pattern, a limitation acknowledged in prior research where fixed sensors can restrict movement and obscure accurate kinematic capture (Werner et al., 2023). This methodological factor is hypothesized to contribute to the observed gait differences between SCI and control groups. Such subjective influences may compromise analytical objectivity and increase data variability. Consequently, we suggest that clinical gait assessment integrate multimodal quantitative approaches. For instance, coupling biomechanical data with electroencephalography and functional near-infrared spectroscopy could elucidate cortical dynamics and neurovascular coupling during walking, thereby advancing future research into gait control and rehabilitation in SCI (Wu et al., 2025).

Gait function and neuromuscular control strategies in persons with incomplete SCI are affected by age. Divergent gait patterns were exhibited by persons across different age groups. The walking ability of young SCI persons was weaker compared to middle aged and elderly SCI persons with the same level. This discrepancy may be related to differences in injury mechanism and age-specific expectations of walking ability. The changes in gait strategy, balance control, and muscle activation patterns in persons with incomplete SCI provide an important bio-mechanical and neurophysiological basis for the development of age-specific rehabilitation intervention plans.

This study has several limitations. Firstly, this study primarily focused on analyzing the gait and muscle activation characteristics of SCI persons across different age groups, without investigating other confounding factors affecting gait, such as spasms. Secondly, the gait behavior exhibited by SCI persons is highly individualized. Due to the inability of persons to perform multiple trials, only two trials were collected for each person. Further research involving a larger population is required to confirm the proposed results. In addition, there was inconsistency in the number of persons using ankle-foot orthotics collected in this study, which may have impacted the results. In the future, it is necessary to strictly control the number of persons using ankle-foot orthotics, or include those who can walk independently to improve result accuracy.