There are many reports analyzing athletes of various disciplines in the context of physical performance and/or injuries. During training, the body undergoes transformations not only within the myofascial system, but also specific adaptation in many organs and systems. While internal organs undergo changes at a slower rate and are able to adapt more easily, disruptions in function of the motor apparatus may manifest faster and with greater effects . Errors in a body posture associated with an abnormal inspiratory or expiratory chest position can be a basis for progressive postural dysfunction, with a loss of functional diaphragm tension and muscle stabilization of the torso [2, 3]. Pinheiro et al. showed a decrease in respiratory muscle strength and related changes in the thoracic-abdominal breathing track after experiencing stroke . Disorientation of body posture that starts from the neck may be dependent on the breathing mechanism. Breathing through the mouth, which is associated with a lower MIP value, promotes frontal inclination of the head, limiting the diaphragm and chest expansion .
There were no significant differences in the MIP and MEP parameters correlated with body weight and BMI in our study population. Despite varied physical activities, all participants were characterized by similar anthropometric features. Other studies observed that differences in the maximum values of respiratory muscle pressure were generally related to BMI classification, as well as the environment [8, 9]. The published reference values MIP and MEP show high variability depending on the population, measurement method, and applied test methodology, as reported by Leech et al. , Ringqvist  and Cook et al.  (Table 2). The values we obtained are most similar to those given by Leech et al., specifically for 13–35 year-old women. The observation that maximum muscle pressure was greater in soccer players indicates that expiratory muscle strength (mainly the abdominal muscles) may be a result of increased activity, causing stimulation of breathing with physical exertion. These changes also support inspiration due to the increased initial length of diaphragm fibers. Watsford et al. also observed a higher MEP value for athletes, and stated that it can contribute to improving the efficiency of the system .
According to our knowledge, this is the first study that analyzes MIP and MEP results with the body posture of women practicing soccer, an endurance sport with high energy consumption. The body posture of the soccer players indicated a rate of asymmetry of the vector that was twice as high as controls. Conversely, the control group demonstrated greater asymmetry of the vector. These differences support the idea that continuous changes occur in the location of selected bone points as a consequence of unstable posture, but also illustrate disturbances in static muscle balance. It is assumed that functional postural dysfunctions, like the effects of frequently repeated aversive movement patterns, modulate neuromuscular stimulation in the torso muscles, with simultaneous regulation of the pressure in the abdominal cavity and chest . An example of a dysfunction that modulates the efficiency of the respiratory system is the upper-junction syndrome, which is accompanied by a pattern of breathing using only the upper fibs, followed by potentially harmful cervical spine disorders, reduced diaphragmatic efficiency, and adaptive tonus changes in the muscles. The correlation between bending strength, straightening of the cervical spine, and the strength of the respiratory muscles was described by Dimitriadis et al. for a group of 45 people with chronic neck problems. The MIP (r=0.35) and MEP (r=0.39) values decreased by 13.8% and 15.4%, respectively, in these patients compared healthy controls . Wirth et al. analyzed neck pain in the context of MIP and MEP changes, and implicated the need to perceive musculoskeletal deficits in the spine and chest in the regression of respiratory muscles .
We did not observe any significant influence of OCL and OCR points asymmetry on the maximal inspiratory and expiratory muscle strength with any of the analyzed body positions in the control group. There was only a tendency for correlation between the MIP and the angle between the horizon and vector in the actively corrected position, the mechanism activating the postural muscles. The rotational positioning of the head in space is often accompanied dislocation of the scapulae. The increased asymmetry of the left trigonum spina scapulae and left inferior scapular angle in the soccer players may be related to clinical upper-cross-over syndrome, i.e. tension and shortening of the upper part of the trapezius, levator scapulae, and sternocleidomastoid. Left scapulae dislocation in the soccer players may result from repeated left upper limb movements used to coordinate the right leg while leading and/or kicking the ball. The MIP and MEP mean values were used to analyze the myofascial upper-torso with the strength of the respiratory muscles, with an inversely proportional dependence of scapular position on maximum inspiratory pressure in the soccer players. No similar reports were found in the literature, indicating a need for further assessment.
Among the studied groups, the correlation between respiratory muscle strength and increased pelvic asymmetry was not observed. However, it can be assumed that inspiratory and expiratory muscles training would have had an indirect beneficial effect on the perception of body posture [3, 21, 22, 31].The present study was a pilot study, and only considered the assessment of body posture in the dorsal coronal plane, which possessed minimal initial correlation with the role of respiratory muscles. A noticeable limitation of the presented research is the variability of MIP and MEP values, related to the number of repetitions performed for each maneuver and how they are interpreted. Further tests require an increased number of repetitions. Unfortunately, this would significantly increase the time designated for each procedure, which affects both the researchers and participants.