## 2 Materials and Methods  
For this study, we utilized the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines [48]. Using the PubMed, Scopus, and ProQuest databases, all authors independently performed a literature search using the following keyword combinations: static stretching, passive stretching, neural response, motor evoked potential, H-reflex, tendon reflex, stretch reflex, excitability, muscle architecture, fascicle length, pennation angle, muscle thickness, muscle stiffness, tendon stiffness, shear elastic modulus, shear wave speed, and shear wave elastography; for example, \"(\"static stretch\" OR \"passive stretch\" OR \"static stretching\" OR \"passive stretching\") AND (\"neural response\" OR \"motor evoked potential\" OR \"H-reflex\" OR \"tendon reflex\" OR \"stretch reflex\" OR excitability OR \"muscle architecture\" OR \"fascicle length\" OR \"pennation angle\" OR \"muscle thickness\" OR \"ultrasound\" OR \"muscle stiffness\" OR \"tendon stiffness\" OR \"shear elastic modulus\" OR \"shear wave speed\").\" We also found some relevant studies from the references of the selected articles and from a personal library. The PRISMA flow diagram is shown in Figure 1.  
The inclusion criteria were as follows: (1) peer-reviewed research articles published in English between January 2012 and December 2022; (2) adults aged 18-50 with no history of serious injury or an ongoing injury (non-athletic and athlete population); (3) static/passive stretching in a single session (acute) or multiple sessions (chronic), targeted lower extremity joints, not combined with other interventions (e.g., voluntary contraction, electrical stimulation); (4) each intervention session dedicated to only one muscle group, not multiple joints or different muscle groups; (5) pre-post comparison of at least one of the aforementioned outcome variables. The exclusion criteria were as follows: (1) participants with neurologic or musculoskeletal injuries; (2) any of the aforementioned outcome measuresnot available; and (3) other types of publications (e.g., reviews, book chapters, conference proceedings/abstracts, theses, dissertations).  
By extracting the necessary information from the reviewed studies (e.g., the number of participants, mean and standard deviation of available outcomes), meta-analyses were conducted to provide more precise estimates of the acute and chronic effects of static stretching on neuromuscular properties. Considering that many studies also reported joint behaviors such as range of motion (ROM), passive resistance torque (PRT), maximum tolerable PRT (PRT\({}_{\text{max}}\)), maximum voluntary isometric torque (MVIT), and muscle-tendon unit (MTU) stiffness, these parameters were also considered in the meta-analyses.  
All the statistical analyses were performed using IBM SPSS Statistics (Version 28, IBM SPSS Inc., Chicago, IL, USA) [49]. Briefly, a random effects model with restricted maximal likelihood estimation was chosen to account for the heterogeneity between the studies. The effect size was calculated using [PERSON]'s \(d\), and \(d\) values of 0.2, 0.5, and 0.8 are considered to indicate small, moderate, and large effect sizes, respectively [50]. The \(I^{2}\) statistic was used to assess the degree of heterogeneity, and \(I^{2}\) values of 25%, 50%, and 75% are considered to indicate low, moderate, and high heterogeneity, respectively [51]. If an outcome measure was not available from at least two studies, a meta-analysis for the outcome measure was not performed.