## 1 Introduction  
Sarcopenia, a progressive loss of skeletal muscle mass and function, significantly contributes to mobility impairments, physical frailty, and increased risks of falls, hospitalization, cardiovascular diseases, respiratory diseases, cancer mortality, and all-cause mortality in older adults [1, 2]. However, alterations in gait patterns and balance among the elderly are multifactorial, encompassing not only sarcopenia but also neurological disorders (e.g., Parkinson's disease, stroke), sensory impairments (e.g., vestibular dysfunction, peripheral neuropathy), musculoskeletal conditions (e.g., osteoarthritis), and polypharmacy effects [3, 4]. While these factors collectively influence mobility, sarcopenia remains a critical and modifiable risk factor, as defined by the Asian Working Group for Sarcopenia (AWGS) through criteria such as low muscle mass, reduced muscle strength, and poor physical performance [5]. Given its substantial impact on physical function and quality of life, the early detection of sarcopenia is critical for implementing timely interventions, yet its specific contribution to gait variability amidst these other causes warrants further exploration.  
Among older adults, those aged 75 years and above face a particularly heightened risk of sarcopenia-related mobility impairment. Evidence suggests that muscle mass and function decline more rapidly in this age group, resulting in greater susceptibility to gait disturbances, increased fall risk, and diminished independence [3]. Despite the well-documented importance of mobility assessments, traditional screening methods for sarcopenia--such as gait speed, grip strength, and muscle mass measurements--may not fully capture subtle neuromuscular changes that contribute to mobility decline [4,6]. In this context, spatiotemporal gait parameters, including stride length, step variability, and double-limb stance duration, have gained attention as potential indicators of sarcopenia-related impairments [7]. These gait characteristics reflect underlying deficits in muscle coordination, strength, and balance control, offering a more comprehensive understanding of mobility limitations in aging populations [8].  
Despite emerging evidence linking gait parameters to sarcopenia, the correlation between specific spatiotemporal gait characteristics and declines in muscle mass and physical performance--defined as reduced functional capacity in gait speed, balance, or lower extremity strength, as measured by the short physical performance battery (SPPB)--remains underexplored in older adults [9]. Additionally, while wearable sensor-based gait analysis technologies offer valuable insights into mobility impairments, their integration into routine clinical assessments remains limited due to variability in protocols and measurement standardization [10].  
This study aims to investigate the associations between muscle mass decline, poor physical performance, and spatiotemporal gait parameters (e.g., stride length, double-limb stance, gait speed) in community-dwelling Korean older adults aged 75 years and above. We seek to enhance early detection strategies and contribute to the development of targeted interventions for preserving mobility and independence in aging populations, particularly within the context of sarcopenia as a modifiable risk factor among multiple contributors to gait alterations.