Changes of the body posture in the sagittal plane of young adults during Matthiass test

Background Postural assessment is an important part of the physical examination in the physical therapy practice. One of the most commonly used clinical tests is an arm-raising Matthiass test. The aim of this study was to investigate posture changes in sagittal plane observed during Matthiass test in young adults using a rasterstereography method. Methods Fourteen young and healthy volunteers, nine female and four male aged between 21 and 25 took part in this study. Examination s performed with the rasterstereographic measuring device. Results Trunk inclination significantly decreased during Matthiass test and the pelvis inclination increased. Distance between kyphosis apex and cervical lordosis apex was significantly shorter during the test than in standing position. Distance between kyphosis apex and lumbar lordosis apex significantly increased during Matthiass test. Kyphosis angle was significantly decreased and the lumbar lordosis angle was increased during the test. Conclusion The results of this study suggest that Matthias test can cause significant deviations in posture in young participants. Changes in the sagittal plane are observed mainly right after the elevation of the arms.


Introduction
Body posture can be described as the orientation of body segments relative to the gravitational vector [1]. Posture deformities can be a serious problem in developing countries due to a sedentary lifestyle. Posture examination is an important part of the physical examination in physical therapy practice. One of the most widely used clinical tests is arm-raising Matthiass test. It evaluates the dynamic postural performance in the sagittal plane during standing with arms lifted forward to 90° shoulder flexion for 30 s.
The Matthiass posture test is dedicated to detecting posture changes in children and adolescents [2]. It is a fast and safe detection method of posture weaknesses. However, visual assessment is subjective. That is why it can lead to inconsistent conclusions. Radiography seems to be an unsuitable method for screening postural deformity in early stages. Moreover, it is risky when used for repeated monitoring because of invasive character. Therefore, various examination methods enabling non-invasive posture assessment have been developed [3,4]. Rasterstereography is one of the radiation-free methods used to analyze the three-dimensional back shape. It has been shown as an accurate tool used for examination postural changes in scoliosis [5][6][7], Scheuermann disease [8], and leg length inequality [9,10]. Previously demonstrated good reliability of rasterstereographic measurements shows their validity and reliability during static measures, such as the Matthiass test [2]. However, it is not clear what kind of postural changes in the sagittal plane are observed in Matthias test after the adolescence in young adulthood.
The aim of this study was to investigate posture changes in the sagittal plane observed during Matthiass test in young adults using the rasterstereography method.

Study design
Fourteen young volunteers, nine female and four male aged between 21 and 25 (mean ± SD: aged 22.14 ± 1.12 years), took part in this study. Participants were healthy, free of any injury or pain for at least a month prior to testing and did not have diagnosed scoliosis or Scheuermann disease.
Subjects gave their written informed consent to participate in this examination. Position of the pelvis can be drawn because the lumbar dimples are in close relation to the underlying posterior superior iliac spines of the pelvis. Positive pelvis inclination means forward tilt and negative values mean backward tilt of the pelvis. Trunk inclination was calculated as the distance in the sagittal plane between the VP and the middle point between lumbar dimples. A positive value was interpreted as an increase in inclination in an anterior direction [12,13]. Kyphosis angle was calculated between inflectional point cervicothoracic and inflectional point thoracolumbar, lumbar lordosis angle was calculated between inflectional point thoracolumbar and inflectional point lumbosacral.
Rasterstereographic method previously occurred as a reliable tool for examination of healthy volunteers posture in the sagittal plane [14,15].
According to previous studies, participants were instructed to stand with their feet shoulder-width apart, looking straight ahead [16].

Results
Trunk inclination significantly decreased during Matthiass test from 2.40 to -2.10 deg.
Pelvis inclination was increased in Matthias 2 comparing to a normal standing position and Matthiass 2 only in trunk inclination and K-LL. Table 1 shows the median and ranges of parameters and Table 2 shows statistic results and p-values.   Table 3. Figure 1 shows changes of K-CL and K-LL during backward trunk lean.

Discussion
Most studies in the field of posture evaluation have focused only on the school children or adolescents and too little attention has been paid to early adulthood. Thus, the aim of this study was to analyze posture changes in sagittal plane observed during Matthiass test in young adults using the rasterstereography method.
In this study, we investigated the trunk inclination changes from the positive value (trunk forward) to negative (trunk backward). Betsch et al. investigated healthy adolescents in modified Matthiass test with additional weight held in hands. They noticed an increase of the trunk inclination from -4.7deg to 1.3deg [12]. Our findings are in agreement with Albertsen et. al. who noticed that in healthy children (10-14 years) backward lean of the trunk and lumbar lordosis increased [17]. Pelvic inclination has not been investigated previously during posture tests. and kyphosis angles in adolescents were about 30 degrees [12].

In this study kyphosis and lordosis angles in
We have noticed a small but statistically significant increase in lumbar lordosis, which is consistent with previous studies [12,17] Kyphosis angle in our study significantly decreased when arms were lifted. Significant reduction of the kyphosis angle caused by elevating limbs was previously reported by Betsch et al. [12]. but not by Albertsen et al. It is interesting that postural changes are involved immediately after arms lifting. During a period of 30 s, only trunk inclination decreased and K-LL increased significantly without significant changes of other parameters. Probably the posture mechanism is related to the ankle joint strategy for saving balance [1]. The main limitation of this study was a small sample size. This investigation needs to be repeated in a larger number of participants to confirm our results.

Conclusions 9
The results of this study suggest that Matthias test can cause significant deviations in posture in young participants. Changes in sagittal plane are observed right after the elevation of the arms. After the 30 s only trunk backward lean significantly increased. This finding provides further support for the hypothesis that Matthiass test leads to a significant reduction of the kyphosis angle and increased lumbar lordosis.

Declarations
Availability of data and materials All data used and analysed during the current study are available from the corresponding author on reasonable request.