###### Abstract  
(1) Background: The rise in sedentary lifestyles has led to more spinal malformations in the population. These malformations are connected to the body's autonomic function, which can negatively impact long-term health. Heart rate variability can be used as a marker to measure how different postures affect autonomic health. This systematic review aims to explore the link between posture and heart rate variability and evaluate potential interventions to address the consequences of sedentary lifestyles. (2) Methods: Data sources: Studies exploring the relationship between posture and heart rate variability were found using PubMed, Embase, Web of Science, and Cochrane on 1 July 24. Eligibility criteria: People aged 18 years or above with a sedentary lifestyle were included. Studies involving children or participants with spinal/musculoskeletal conditions impacting their ability to walk or sit were excluded as they would not accurately reflect posture analysis. PRISMA guidelines were followed throughout, and the quality assessment was achieved using the QualSyst tool. (3) Results: Out of the 753 papers identified, only five met the eligibility criteria. These studies exhibited heterogeneity regarding interventions, aims, and participant populations. All five studies were prospective case series, enabling analysis and comparisons. (4) Conclusions: According to this study, the seated position, especially the forward truncal flexion, had the most significant impact on heart rate variability and sympathetic tone. It may be inferred that sedentary behavior encourages this stress on the body, which can affect one's health, increasing the mortality rate.  
heart rate variability; posture; sedentary behavior; autonomic function; sitting position +
Footnote †: journal:influenced by parasympathetic activity via the vagus nerve, is considered a hallmark of a resilient and responsive cardiovascular system [4; 5].  
However, this intricate balance can be disrupted by a myriad of factors, leading to alterations in HRV, which are increasingly recognized as indicators of compromised health. While numerous physiological and pathological influences on HRV are well-documented, the impact of lifestyle factors, particularly posture and sedentary behavior, has emerged as a critical area of investigation.  
The modern world, characterized by technological advancements and increasingly sedentary occupations, has inadvertently fostered a lifestyle that often prioritizes convenience over movement [6]. This shift toward sedentary behaviors, characterized by prolonged periods of sitting and minimal physical activity, has raised concerns about its potential effects on autonomic health. Sedentary behavior is often intertwined with poor posture, which can lead to musculoskeletal imbalances and potentially impact physiological processes beyond the musculoskeletal system [7].  
Emerging research suggests a complex interplay between posture, sedentary behavior, and HRV. Prolonged sitting, especially in positions that compromise spinal alignment, may alter autonomic function, potentially leading to a reduction in HRV [1]. Also, posture affects one's biomechanics, musculoskeletal health, and physiological processes [8]. This potential link between postural habits, sedentary lifestyles, and autonomic dysregulation underscores the need for a comprehensive understanding of these interactions to develop effective strategies for promoting health and well-being.