## 1 Introduction  
Pelvic floor muscle (PFM) dysfunctions, such as urinary incontinence (UI), significantly impact women's quality of life, affecting physical, emotional, and social well-being [1, 2]. The conservative approach consisted of PFM training through voluntary contractions. Nevertheless, breathing and abdominal-based programs have gained popularity among pelvic floor therapists for the treatment and prevention of PFM dysfunctions. Among these programs, abdominal hypopressive technique (AHT) has emerged as a promising technique [3]. Initially, AHT was conceptualized to reduce intra-abdominal pressure through specific breathing maneuvers and well-defined postures to improve PFM basal tone [4]. AHT applications have expanded to address a broader spectrum of pelvic floor disorders such as pelvic organ prolapse [5] and urinary incontinence [3]. However, the current literature on clinical and non-clinical trials using similar training or rehabilitation techniques remains scattered and lacks a systematic review of their effectiveness. Previous studies have examined alternative methods, such as Kegel exercises, biofeedback training, and functional electrical stimulation in order to improve PFM functionality [6; 7]. These approaches have been compared to AHT, but there is still no consensus regarding their relative effectiveness, particularly in terms of muscle contractility and endurance. Moreover, fewer studies have examined its direct impact on muscle contractility, load absorption, and muscle efficiency [7]. Additionally, the neurophysiological mechanisms underlying AHT's effects on neuromuscular coordination and muscle endurance remain poorly understood. AHT influences PFM activation through a combination of specific postures and diaphragmatic breathing. During AHT, a full exhalation is followed by apnea with ribcage expansion, triggering a reflex contraction of the deep core muscles, including the transversus abdominis and PFMs [8]. This maneuver creates negative intra-abdominal pressure, inducing involuntary diaphragm elevation and co-activation of the PFMs [4]. Additionally, the synchronization between diaphragmatic breathing and PFM activation enhances neuromuscular coordination and muscle efficiency [9]. The integration of postural techniques in AHT also contributes to the activation of tonic muscle fibers (type I), improving endurance, and postural control of the PFMs [10]. Therefore, AHT may enhance PFM function through neurological mechanisms involving reflex activation and synergistic coordination with the diaphragm and other core stabilizing muscles. Prior research has substantiated the effects of AHT on PFM, demonstrating improvements following structured interventions [6; 7]. Several studies found activation of transversus abdominis, internal oblique, and PFM in healthy female participants, as well as those with PFM disorders [11; 12]. It has been postulated that the specific hypopressive breathing maneuver, also known as abdominal vacuum, in combination with postural adjustments, might contribute to muscle activation of abdominopelvic musculature and fascial mobilization [13; 14]. However, literature exploring the impact of AHT on PFM contractility remains scarce. To provide a more comprehensive understanding of the field, it is important to discuss different maneuvers used in related studies and how they compare them to those implemented in our research. For instance, studies such as [PERSON] et al. [5] have examined the combination of AHT with other interventions, whereas [PERSON] et al. [15] have assessed the differences between training modalities, including active and passive muscle stimulation. These studies highlight the need to consider multiple training parameters, such as duration, frequency, and intensity, to optimize results. Our study aims to contribute to this growing body of evidence by focusing specifically on PFM strength improvements resulting from a systematic AHT program.