Relationships Between Postural Quality and Postural Stability Among Healthy Young Adults

Abstract

Purpose: This study aimed to determine whether apparent differences in body posture affect the ability to maintain balance and foot loading during standing. Methods: The research was conducted in a group of 100 young adults. The examinations included measurements of body posture using the Posture Photographic Assessment System, as well as measurements of balance ability using the Zebris FDM-S platform. The following body posture parameters were analyzed: posture index (PI), pelvic tilt angle (PLT), and the tilts of subsequent spinal segments. Participants’ body posture was categorized according to the classifications proposed by Dolphens and Frohner. The analyzed balance parameters included the path length (PL) covered by the center of foot pressure (COP) on the ground and the ellipse area (EA) in which the COP was located during the test. The mean percentage load on the forefoot (FORE) and rearfoot (BACK), as well as the symmetry index (SI) for the load on the right and left foot, were also analyzed. Results: Kruskal–Wallis tests demonstrated that PL, EA, SI, FORE, and BACK did not differ significantly among the three posture types defined by Dolphens nor among participants with different pelvic alignments. Furthermore, PL, EA, SI, FORE, BACK, PLT, and the tilts of subsequent spinal segments did not differ significantly between the two posture types according to Frohner. Conclusions: Balance parameters and foot loading during standing did not differ significantly among the three posture types defined by Dolphens, between the two posture types according to Frohner, or among participants with different pelvic alignments.

1. Introduction

Maintaining an upright posture in humans is a complex process controlled by multiple biomechanical and neurophysiological mechanisms [1]. Postural disorders are characterized by noticeable alterations in body posture, such as excessive lumbar lordosis, thoracic kyphosis, increased anterior pelvic tilt, or head protraction [2,3,4]. These disorders result from abnormal neuromuscular balance [5], which contributes to overload of the musculoskeletal system and, consequently, pain in adulthood [6]. These effects may be exacerbated by increased strain or by performing everyday activities in a non-ergonomic manner [7]. Intrinsically related to body posture is the concept of postural control, which refers to the ability to maintain body balance and to regain it when body segments are displaced [8].

Balance control mechanisms are associated with neurophysiology and neuromuscular control processes [9,10]. These mechanisms include both macroscopically visible changes in the alignment of individual body segments and small, measurable body sway resulting from central nervous system control of the muscles responsible for maintaining correct body posture [1,10].

Certain deviations in posture can adversely affect muscular efficiency, as well as predispose individuals to musculoskeletal pathological conditions [11]. Postural assessment remains challenging, as current assessment methods are still scientifically imprecise. Two methods are widely used for such assessments: analysis of the projection of the center of gravity using a force platform and photographic assessment of standing posture [12]. Posture is strongly related to balance. While it is difficult to conceive of good posture coexisting with poor balance, it is possible to imagine poor posture with good balance if misaligned body segments are compensated so that the resulting projection of the center of gravity remains between the feet [13]. In this study, the photometric method, a simple and relatively inexpensive method enabling posture assessment, was used to assess postural quality. The reliability and reproducibility of this method have been reported repeatedly in the literature [14,15]. Postural assessment using photography is a simple method that allows the acquisition of quantitative data to define the alignment of body segments [16]. This method enables angular calculations based on anatomical reference points and provides a digital, more objective approach to measurement. Reliability studies of manual photographic posture analysis have also been conducted investigating subjects other than adults [17]. Clinical use of photographic posture analysis is recommended in the literature because it is an accurate and objective method [18]. The examinations of postural quality were supplemented by an evaluation of postural quality. There is ongoing discussion in the literature regarding optimization of methods and techniques for the interpretation of posturographic data. Furthermore, there is an ongoing search for new methods enabling the reliable assessment of postural stability, including the use of virtual reality, to reveal unambiguous relationships between body sway and postural stability [19,20,21,22,23].

In the present study, a static posturography method was used to investigate the quality of postural control.

The primary question asked in this study was whether apparent differences in body posture affect the ability to maintain balance and foot loading during standing.

2. Materials and Methods

2.1. Study Design

This cross-sectional observational study was conducted in accordance with the principles of the Declaration of Helsinki and the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for reporting observational studies [24]. The study design was approved by the Bioethics Committee of the Jerzy Kukuczka University of Physical Education, Katowice, Poland, prior to study commencement (Decision No. 3/2019). All participants were informed about the purpose and procedures of the study and provided written consent voluntarily.

2.2. Setting

The study was conducted from October 2021 to June 2022 at the Research Centre of the Silesian University of Technology.

2.3. Participants

The study group consisted of 100 adults of both sexes, aged 20 to 24 years, with 47 men and 53 women.

Participants were eligible for the study if they met the following inclusion criteria: age between 19 and 29 years; absence of visible musculoskeletal dysfunction, defined as the lack of confirmed musculoskeletal disorders; and normal body weight, determined on the basis of body mass index (BMI).

Exclusion criteria included: the presence of disorders affecting the central nervous system and/or the musculoskeletal system that may impair normal psychomotor development; conditions potentially leading to postural pathology, including genetic syndromes, hormonal disorders, neuromuscular diseases, and congenital musculoskeletal defects; abnormal body weight (underweight, overweight, or obesity); and lack of written informed consent.

2.4. Intervention

Prior to commencement of the stabilometric tests conducted using the Zebris FDM-S platform (Zebris Medical GmbH, Isny, Germany), participants received detailed instructions regarding the test methodology and the requisite perfomance thereof, i.e., with eyes open and eyes closed. Participants were instructed to maintain a standing position for 60 s during each trial. During the test, participants assumed a relaxed standing position with their feet positioned hip-width apart. Participants were instructed to maintain this position without intentional movement of the head or upper limbs, which were allowed to move freely, and to look straight ahead. Furthermore, participants were given the opportunity to familiarize themselves with the platform and to perform a single unrecorded trial lasting several seconds. During the experimental procedure, only the participant and the experimenter were present in the room. To minimize the influence of extraneous factors, the testing environment was maintained at a low noise level. Prior to commencement of each trial, the platform was calibrated. The platform was designed to assess balance using two tests: standing with both feet and eyes open, and standing with both feet and eyes closed. Each trial lasted 60 s; a sampling frequency amounted to 100 Hz. A one-minute interval was observed between recorded trials. For each trial, three measurements were performed, and the final result was calculated as the average of the measurements. The measurement was initiated once the participant was prepared and had adopted the appropriate initial posture.

The OPIW Posture Analysis System (utility model W 118191, Patent Office of the Republic of Poland) consists of the following components:

• digital camera equipped with a tripod;
• fold-out board with a printed posturographic grid and a marked mini platform;
• podoscope with a built-in webcam;
• computer with a printer;
• Posture_Screening computer programme. (Figure 1).

The following procedure constituted a preparatory step prior to the examination. Participants were required to wear swimwear appropriate to their sex (i.e., women should wear two-piece swimsuits). Subsequently, selected measurement points on the participant’s body were marked (using a dermograph or stickers). The participant’s posture was recorded from the side, with the participant standing in a relaxed position lateral to the posturographic board and with the feet positioned perpendicular to the center line marked on the platform. For all tests, the recommended camera setting was at half of the participant’s body height and at a distance of 250 cm from the board.

2.5. Outcome Measures

The examinations included measurements of body posture and ability to maintain balance.

Assessment of body posture was carried out using the Posture Photographic Assessment System (OPIW, Opole Innovative and Implementation Company, Opole, Poland). The division into three posture types proposed by Dolphens [25] was used to assess postural balance. The classification proposed by Dolphens divides body posture into three types: balanced posture (Bal.), lordotic posture (Lord.), and kyphotic posture (Kyph.) [25,26]. According to this classification, balanced posture predominated in the study group (

Table 1. Number of posture types according to Dolphens’ classification in the study group.

Type of Posture	Bal	Lord	Kyph
All	60	30	10
Women	25	25	3
Men	35	5	7

(Bal—balanced posture, Lord—lordotic posture, Kyph—kyphotic posture).

).

According to the classification proposed by Frohner, which distinguishes three posture types, i.e., neutral (N), sway-back (SB; frontal arch), and lordotic (L), the study group was dominated by postures characterized by increased curvatures (I) (

Table 2. Number of posture types according to Frohner classification in the study group.

Type of Posture	N	I (SB+L)
All	45	55
Women	27	26
Men	18	29

(N—neutral posture, I—posture with increased curvatures, SB—sway-back, frontal arch and L—lordotic posture).

) [27].

The following parameters were included in the postural examinations:

• ALPHA—lumbosacral tilt angle;
• BETA—thoracolumbar tilt angle;
• GAMMA—upper kyphosis tilt angle;
• PI—Frohner posture index;
• LRD—angle of lumbar lordosis;
• KPH—angle of thoracic kyphosis;
• PTL—pelvic tilt in the sagittal plane.

Based on pelvic tilt (PTL) measurements, the participants were divided into three groups as proposed by Bibrowicz [28]: AP—participants with anterior pelvic tilt, BP—participants with balanced pelvis tilt, and PP—participants with posterior pelvic tilt) (

Table 3. Types of pelvic tilt in the study group.

	Type of pelvis	AP (>12°)	BP (≥12°≤20°)	PP (<19°)
Women	n	15	36	2
	Type of pelvis	AP(>12°)	BP (≥12°≤19°)	PP (<19°)
Men	n	3	35	9

(AP—anterior pelvic tilt, BP—balanced pelvis, PP—posterior pelvic tilt, n—group size).

).

Balance measurements were performed using the Zebris FDM-S measurement platform (Zebris Medical GmbH, Isny, Germany), with a sampling rate of 100 Hz.

The balance test, involving analysis of the position of the net force of foot pressure on the ground, was based on the Romberg test.

The following parameters were analyzed:

PL—path length [mm]—total length of the path covered by the COP (the path covered by the center of foot pressure on the ground during the measurement),

EA—ellipse area [mm²] where the COP was located during the test (area of the ellipse formed by 95% of the COP locations during the examination),

SI—symmetry index for the average percentage load on the right and left foot [29,30]:

$$SI={\displaystyle \frac{(L-R)}{\mathrm{m}\mathrm{a}\mathrm{x} (L,R)}}\ast 100\%$$

where

• L—percentage load on the left foot;
• P—percentage load on the right foot;

Mean percentage load on the forefoot (FORE) and rearfoot (BACK) [%]

$$FORE={\displaystyle \frac{FOR{E}_L+FOR{E}_R}{2}}$$

$$BACK={\displaystyle \frac{{BACK}_L+{BACK}_R}{2}}$$

where

• ${FORE}_L$—percentage load on the left forefoot;
• ${FORE}_R$—percentage load on the right forefoot;
• ${BACK}_L$—percentage load on the left rear foot;
• ${BACK}_R$—percentage load on the right rear foot.

The analyzed quantities were determined on the basis of a 30 s measurement, from the 15th to the 45th second.

2.6. Statistical Analysis

The obtained results were analyzed statistically. Quantitative variables of parameters were described using the arithmetic mean, standard deviation, and medium value. Normality of distribution was verified using the Shapiro–Wilk test. Differences in the analyzed parameters between groups defined according to Dolphens’ classification or groups with different pelvic arrangements were assessed using the Kruskal–Wallis test. Intergroup differences were identified using post hoc Wilcoxon tests. To assess differences in stabilometric parameters (pelvic inclination angles and other spinal segments) between the two posture types according to Frohner’s classification, Student’s t-test for independent samples or Mann–Whitney U test was used, depending on the normality of the distribution of the analyzed variables. The level of significance adopted in the statistical analyses was α = 0.05. Calculations were performed using Statistica 13.1 software (StatSoft).

3. Results

In total, 125 individuals were qualified for the study, of whom 100 met the eligibility criteria. The qualification process is presented in Figure 2.

Table 4. Study group.

Variable	Women n = 53	Men n = 47
	Mean ± Std.	Mean ± Std.
Weight (kg)	66.00 ± 11.00	82.00 ± 13.00
Height (cm)	166.69 ± 6.02	179.5 ± 5.61

presents the respondents’ anthropometric data.

This study investigated the relationship between postural types and the quality of postural control.

Table 5. Stabilometric parameters, lower limb loads, posture index according to Frohner, pelvic tilt angles, and tilt angles of subsequent spinal segments across the three posture types defined by Dolphens.

Entire group (women and men; n = 100)
	Bal. (n = 60)	Lord. (n = 30)	Kyph. (n = 10)	p-value, Kruskal–Wallis	Post hoc test	p-value 1 vs. 2	p-value 1 vs. 3	p-value 2 vs. 3
	Mean ± Std (median)	Mean ± Std (median)	Mean ± Std (median)
PL	350.5 ± 102.49 (332.15)	324.75 ± 55.15 (325.9)	332.88 ± 66.61 (324.9)	0.5804	N/A	N/A	N/A	N/A
EA	107.76 ± 141.85 (73.8)	107.91 ± 68.01 (91.4)	84.84 ± 65.80 (78.4)	0.4803	N/A	N/A	N/A	N/A
SI	11.51 ± 9.62 (9.70)	10.87 ± 6.98 (9.34)	13.58 ± 6.40 (14.81)	0.6506	N/A	N/A	N/A	N/A
FORE	47.19 ± 11.41 (47.05)	44.17 ± 8.48 (45.95)	51.44 ± 10.52 (52.4)	0.1111	N/A	N/A	N/A	N/A
BACK	52.81 ± 11.41 (52.95)	55.83 ± 8.48 (54.05)	48.56 ± 10.52 (47.6)	0.1111	N/A	N/A	N/A	N/A
PI	1.33 ± 0.11 (1.34)	1.26 ± 0.12 (1.23)	1.42 ± 0.14 (1.49)	0.0006 *	Wilcoxon	0.0047 *	0.0611	0.0073 *
PTL	16.81 ± 4.36 (17)	20.14 ± 4.18 (20.5)	13.39 ± 3.51 (14)	0 *	Wilcoxon	0.001 *	0.016 *	0.0005 *
ALPHA	19.77 ± 5.39 (19)	23.10 ± 4.87 (24)	14.54 ± 5.27 (15.45)	0.0001 *	Wilcoxon	0.0072 *	0.0072 *	0.0009 *
BETA	8.6 ± 4.64 (8.25)	8.60 ± 4.56 (8)	8.07 ± 3.55 (8.5)	0.9988	N/A	N/A	N/A	N/A
GAMMA	25.52 ± 5.11 (25)	22.38 ± 4.31 (22.5)	25.9 ± 6.81 (26.5)	0.0231 *	Wilcoxon	0.0291 *	0.6741	0.1384
LRD	28.38 ± 7.39 (28.7)	31.7 ± 6.09 (32)	22.61 ± 5.64 (24.1)	0.0021 *	Wilcoxon	0.0645	0.0645	0.0014 *
KPH	34.14 ± 7.12 (33)	30.98 ± 6.39 (31)	33.96 ± 7.13 (33.4)	0.2335	N/A	N/A	N/A	N/A
Women (n = 53)
	Bal. (n = 25)	Lord. (n = 25)	Kyph. (n = 3)	p-value, Kruskal–Wallis	Post hoc test	p-value 1 vs. 2	p-value 1 vs. 3	p-value 2 vs. 3
	Mean ± Std (median)	Mean ± Std (median)	Mean ± Std (median)
PL	360.39 ± 81.11 (354)	331.51 ± 57.10 (334.9)	337.03 ± 62.77 (317.7)	0.2768	N/A	N/A	N/A	N/A
EA	93.38 ± 68.09 (70.4)	104.83 ± 69.16 (89.6)	44.93 ± 27.32 (36)	0.2175	N/A	N/A	N/A	N/A
SI	12.99 ± 8.79 (13.43)	10.86 ± 6.97 (9.52)	13.14 ± 6.64 (15.11)	0.1615	N/A	N/A	N/A	N/A
FORE	42.40 ± 10.77 (40.75)	42.93 ± 7.51 (44.15)	55.23 ± 4.96 (53.15)	0.0711	N/A	N/A	N/A	N/A
BACK	57.6 ± 10.77 (59.25)	57.07 ± 7.51 (55.85)	44.77 ± 4.96 (46.85)	0.0711	N/A	N/A	N/A	N/A
PI	1.34 ± 0.09 (1.36)	1.25 ± 0.12 (1.23)	1.44 ± 0.15 (1.51)	0.0017 *	Wilcoxon	0.0041 *	0.2195	0.0894 *
PTL	18.14 ± 5.2 (18.5)	20.34 ± 3.86 (20)	13 ± 10 (13)	0.0169 *	Wilcoxon	0.1087	0.0968	0.0333 *
ALPHA	22.98 ± 5.31 (23)	23.52 ± 4.43 (24)	15.33 ± 2.08 (16)	0.0436 *	Wilcoxon	0.6196	0.056	0.0416 *
BETA	9.98 ± 4.70 (9)	8.69 ± 4.85 (8)	8.6 ± 2.42 (10)	0.6508	N/A	N/A	N/A	N/A
GAMMA	24.36 ± 4.77 (24)	22.18 ± 4.47 (22)	27.67 ± 1.53 (28)	0.056	N/A	N/A	N/A	N/A
LRD	32.96 ± 6.75 (32)	32.21 ± 5.32 (32)	23.93 ± 1.79 (23)	0.0359 *	Wilcoxon	0.648	0.0424 *	0.0424 *
KPH	34.34 ± 6.88 (32.9)	30.87 ± 6.56 (31)	36.27 ± 2.61 (36)	0.1258	N/A	N/A	N/A	N/A
Men (n = 47)
	Bal. (n = 35)	Lord. (n = 5)	Kyph. (n = 7)	p-value, Kruskal–Wallis	Post hoc test	p-value 1 vs. 2	p-value 1 vs. 3	p-value 2 vs. 3
	Mean ± Std (median)	Mean ± Std (median)	Mean ± Std (median)
PL	343.43 ± 116.02 (318.2)	290.96 ± 27.87 (295.3)	331.1 ± 73.01 (332.1)	0.483	N/A	N/A	N/A	N/A
EA	118.03 ± 177.16 (74.4)	123.28 ± 66.93 (112)	101.94 ± 71.47 (104.8)	0.467	N/A	N/A	N/A	N/A
SI	10.46 ± 10.06 (6.95)	10.91 ± 7.87 (6.58)	12.06 ± 6.14 (13.78)	0.2265	N/A	N/A	N/A	N/A
FORE	50.61 ± 10.74 (50.45)	50.38 ± 11.21 (47.5)	49.81 ± 12.14 (50.9)	0.9733	N/A	N/A	N/A	N/A
BACK	49.39 ± 10.74 (49.55)	49.62 ± 11.21 (52.5)	50.19 ± 12.14 (49.1)	0.9733	N/A	N/A	N/A	N/A
PI	1.32 ± 0.12 (1.32)	1.30 ± 0.15 (1.26)	1.41 ± 0.14 (1.49)	0.2691	N/A	N/A	N/A	N/A
PTL	15.86 ± 3.41 (17)	19.14 ± 6.01 (21)	13.56 ± 4.25 (14)	0.1019	N/A	N/A	N/A	N/A
ALPHA	17.48 ± 4.18 (18)	21.00 ± 6.86 (24)	14.20 ± 6.31 (14.9)	0.1515	N/A	N/A	N/A	N/A
BETA	7.62 ± 4.40 (8)	8.14 ± 3.03 (8)	7.84 ± 4.09 (7)	0.9357	N/A	N/A	N/A	N/A
GAMMA	26.35 ± 5.25 (26)	23.4 ± 3.58 (24)	25.14 ± 8.15 (26)	0.4682	N/A	N/A	N/A	N/A
LRD	25.10 ± 6.02 (24)	29.14 ± 9.43 (32)	22.04 ± 6.74 (24.2)	0.5855	N/A	N/A	N/A	N/A
KPH	34.00 ± 7.38 (34)	31.54 ± 6.09 (31)	32.97 ± 8.38 (30.1)	0.7543	N/A	N/A	N/A	N/A

Bal—balanced posture, Lord—lordotic posture, Kyph—kyphotic posture, PL—length of the COP path, EA—area of the COP ellipse, SI—limb load symmetry index, FORE—mean percentage load on the forefoot, BACK—mean percentage load on the rear foot, PI—postural index, PTL—pelvic tilt, ALPHA—lumbosacral angle, BETA—thoracolumbar angle, GAMMA—upper kyphosis angle, LRD—lumbar lordosis angle, KPH—thoracic kyphosis angle, N/A—not applicable, *—statistically significant differences, n—group size.

presents stabilometric parameters, foot loads, posture index according to Frohner, pelvic tilt angles, and tilt angles of subsequent spinal segments across the three posture types defined by Dolphens.

Kruskal–Wallis tests demonstrated that balance parameters and foot loading during standing (PL, EA, SI, FORE, and BACK) did not differ significantly among the three posture types defined by Dolphens (balanced, kyphotic, and lordotic). No significant differences were observed either in the entire study group or in the male and female groups.

Statistically significant differences in the entire study group (without division by sex) were observed for the following parameters: posture index (PI), pelvic tilt angle (PTL), lumbosacral tilt angle (ALFA), upper kyphosis angle (GAMMA), and lumbar lordosis angle (LRD) across the three posture types defined by Dolphens. Post hoc test results indicated intergroup differences.

Similar results were observed in the female group. Statistically significant differences among the three posture types defined by Dolphens were found for the following variables: posture index (PI), pelvic tilt angle (PTL), lumbosacral tilt angle (ALFA), and lumbar lordosis angle (LRD). Post hoc tests indicated that these intergroup differences were mainly related to differences between the lordotic and kyphotic posture group results.

In the male group, no statistically significant differences were observed in posture indices, pelvic tilt angles, or the positions of consecutive spinal segments among the three posture types defined by Dolphens.

Table 6. Stabilometric parameters, pelvic tilt angles, and tilt angles of subsequent spinal segments across the two posture types according to Frohner [23].

Entire group (women and men; n = 100)
	N (n = 45)	I (n = 55)	Student’s t-test for independent samples or Mann–Whitney U test
	Mean ± Std (median)	Mean ± Std (median)
PL	336.41 ± 105.33 (317.7)	344.78 ± 70.98 (335.9)	0.108
EA	118.56 ± 161.36 (76.8)	94.84 ± 61.69 (78.8)	0.964
SI	11.54 ± 7.23 (12.73)	11.52 ± 9.63 (9.52)	0.547
FORE	45.58 ± 10.65 (45.9)	47.63 ± 10.63 (48.8)	0.228
BACK	54.42 ± 10.65 (54.1)	52.37 ± 10.63 (51.2)	0.228
PTL	17.47 ± 5.04 (17.5)	17.46 ± 4.36 (18)	0.994
ALPHA	20.34 ± 5.71 (20)	20.18 ± 5.77 (19)	0.51
BETA	8.06 ± 4.3 (8)	8.95 ± 4.62 (8)	0.328
GAMMA	24.93 ± 5.45 (26)	24.36 ± 5.08 (24)	0.591
LRD	28.4 ± 7.29 (30.5)	29.12 ± 7.31 (28.6)	0.621
KPH	33.22 ± 7.21 (32.2)	33.14 ± 6.88 (32)	0.958
Women (n = 53)
	N (n = 27)	I (n = 26)	Student’s t-test for independent samples or Mann–Whitney U test
	Mean ± Std (median)	Mean ± Std (median)
PL	336.98 ± 72.16 (334.9)	354.23 ± 67.93 (352.15)	0.375
EA	97.63 ± 68.83 (79.2)	94.39 ± 67.59 (73)	0.957
SI	12.03 ± 6.66 (13.08)	12.42 ± 9.31 (11.85)	0.972
FORE	43.28 ± 7.97 (45.8)	43.48 ± 10.92 (40.95)	0.938
BACK	56.72 ± 7.97 (54.2)	56.52 ± 10.92 (59.05)	0.938
PTL	18.91 ± 4.87 (18.5)	18.87 ± 4.74 (19)	0.977
ALPHA	22.91 ± 4.06 (24)	22.7 ± 6.03 (23)	0.879
BETA	8.98 ± 4.66 (8)	9.61 ± 4.72 (9)	0.627
GAMMA	23.93 ± 5.26 (23)	23.1 ± 4.09 (24)	0.527
LRD	31.89 ± 4.96 (32)	32.31 ± 7.37 (32)	0.81
KPH	32.91 ± 7.32 (32.2)	32.71 ± 6.26 (32)	0.916
Men (n = 47)
	N (n = 18)	I (n = 29)	Student’s t-test for independent samples or Mann–Whitney U test
	Mean ± Std (median)	Mean ± Std (median)
PL	335.55 ± 144.05 (294.55)	336.3 ± 73.74 (324.7)	0.078
EA	149.93 ± 241.68 (76.8)	95.26 ± 57.08 (86)	1
SI	10.82 ± 8.16 (9.84)	10.7 ± 9.99 (8.8)	0.638
FORE	49.04 ± 13.25 (48.05)	51.35 ± 9 (50.9)	0.479
BACK	50.96 ± 13.25 (51.95)	48.65 ± 9 (49.1)	0.479
PTL	15.32 ± 4.61 (16)	16.2 ± 3.63 (17)	0.467
ALPHA	16.47 ± 5.73 (16.5)	17.92 ± 4.54 (18)	0.342
BETA	6.68 ± 3.34 (7)	8.35 ± 4.53 (8)	0.184
GAMMA	26.44 ± 5.53 (26.5)	25.5 ± 5.66 (25.1)	0.576
LRD	23.15 ± 7.17 (22)	26.27 ± 6.05 (25)	0.117
KPH	33.68 ± 7.23 (32.5)	33.53 ± 7.47 (33)	0.947

N—neutral posture I—increased curvature, PL—length of the COP path, EA—area of the COP ellipse, SI—limb load symmetry index, FORE—mean percentage load on the forefoot, BACK—mean percentage load on the rear foot, PI—postural index, PTL—pelvic tilt, ALPHA—lumbosacral angle, BETA—thoracolumbar angle, GAMMA—upper kyphosis angle, LRD—lumbar lordosis angle, KPH—thoracic kyphosis angle, n—group size.

summarizes stabilometric parameters, pelvic tilt angles, and tilt angles of subsequent spinal segments for the two posture types according to Frohner (posture index, PI) [23]. No statistically significant differences were observed in these parameters between the two posture types in the entire study group or in the male and female groups [23].

Table 7. Stabilometric parameters and foot loading in individuals with different pelvic alignments.

Entire group (women and men; n = 100)
	BP (n = 71)	AP (n = 18)	PP (n = 11)	p-value, Kruskal–Wallis	Post hoc test	p-value 1 vs. 2	p-value 1 vs. 3	p-value 2 vs. 3
	Mean ± Std (median)	Mean ± Std (median)	Mean ± Std (median)
PL	332.98 ± 73.34 (324.7)	334.27 ± 84.64 (330.8)	403.88 ± 146.53 (354)	0.2816	N/A	N/A	N/A	N/A
EA	89.13 ± 62.26 (73.2)	102.04 ± 62.64 (86)	216.91 ± 295.16 (129.2)	0.0577	N/A	N/A	N/A	N/A
SI	11.27 ± 8.73 (9.52)	12.38 ± 7.87 (13.08)	11.8 ± 9.44 (10.25)	0.743	N/A	N/A	N/A	N/A
FORE	47.16 ± 10.08 (47.5)	44.95 ± 11.76 (46.65)	46.7 ± 12.91 (42.6)	0.7583	N/A	N/A	N/A	N/A
BACK	52.84 ± 10.08 (52.5)	55.05 ± 11.76 (53.35)	53.3 ± 12.91 (57.4)	0.7583	N/A	N/A	N/A	N/A
Women (n = 53)
	BP (n = 36)	AP (n = 15)	PP (n = 2)	p-value, Kruskal–Wallis	Post hoc test	p-value 1 vs. 2	p-value 1 vs. 3	p-value 2 vs. 3
	Mean ± Std (median)	Mean ± Std (median)	Mean ± Std (median)
PL	343.48 ± 69.08 (343.35)	352.1 ± 78.09 (337.5)	330.95 ± 32.6 (330.95)	0.948	N/A	N/A	N/A	N/A
EA	89.6 ± 69.06 (69.8)	109.87 ± 63.72 (93.2)	108.2 ± 95.32 (108.2)	0.3203	N/A	N/A	N/A	N/A
SI	12.81 ± 8.01 (12.73)	12.18 ± 7.75 (13.43)	1.79 ± 0.28 (1.79)	0.1396	N/A	N/A	N/A	N/A
FORE	44.27 ± 9.54 (42.85)	41.95 ± 9.57 (45.9)	37.88 ± 6.68 (37.88)	0.5482	N/A	N/A	N/A	N/A
BACK	55.73 ± 9.54 (57.15)	58.05 ± 9.57 (54.1)	62.12 ± 6.68 (62.12)	0.5482	N/A	N/A	N/A	N/A
Men (n = 47)
	BP (n = 35)	AP (n = 3)	PP (n = 9)	p-value, Kruskal–Wallis	Post hoc test	p-value 1 vs. 2	p-value 1 vs. 3	p-value 2vs. 3
	Mean ± Std (median)	Mean ± Std (median)	Mean ± Std (median)
PL	322.19 ± 76.97 (311.4)	245.1 ± 62.42 (243.5)	420.09 ± 158.37 (407.7)	0.0308 *	Wilcoxon	0.1613	0.1613	0.1613
EA	88.65 ± 55.43 (76.8)	62.93 ± 46.63 (57.6)	241.07 ± 322.72 (129.2)	0.0419 *	Wilcoxon	0.4815	0.0621 *	0.2
SI	9.68 ± 9.26 (5.83)	13.4 ± 10.22 (12.73)	14.03 ± 8.98 (12.73)	0.1658	N/A	N/A	N/A	N/A
FORE	50.12 ± 9.88 (50.25)	59.92 ± 11.4 (66.3)	48.66 ± 13.38 (52.5)	0.4263	N/A	N/A	N/A	N/A
BACK	49.88 ± 9.88 (49.75)	40.08 ± 11.4 (33.7)	51.34 ± 13.38 (47.5)	0.4263	N/A	N/A	N/A	N/A

BP—balanced pelvis, AP—anterior pelvic tilt, PP—posterior pelvic tilt, PL—length of the COP path, EA—area of the COP ellipse, SI—limb load symmetry index, FORE—mean percentage load on the forefoot, BACK—mean percentage load on the rear foot, PI—postural index, PTL—pelvic tilt, ALPHA—lumbosacral angle, BETA—thoracolumbar angle, GAMMA—upper kyphosis angle, LRD—lumbar lordosis angle, KPH—thoracic kyphosis angle, N/A—not applicable, *—statistically significant differences, n—group size.

presents stabilometric parameters and foot loading during standing across the three pelvic alignment groups (BP, AP, and PP). Statistical analyses indicated no significant differences in balance or foot loading among participants with different pelvic alignments. In the male group, the Kruskal–Wallis test revealed differences for PL and EA; post hoc analyses revealed that ellipse area (EA) was the parameter that significantly differentiated between the BP and PP groups.

4. Discussion

The study demonstrated that posture types classified according to Dolphens’ methodology did not have a statistically significant effect on balance parameters or foot loading. Furthermore, no significant differences in postural balance were observed (as determined by Frohner’s posture coefficient), regardless of strobistatometric variables or the extent of the pelvic tilt in the sagittal plane. The extent of pelvic tilt did not have a significant effect on foot loading measured using the Zebris platform. This finding may appear counterintuitive as it seems to contradict the established knowledge that maintaining appropriate posture facilitates the maintenance of an upright position and thereby limits displacement of the center of gravity in relation to the support surface [31,32,33]. However, it has been demonstrated that ellipse area may differ between individuals with normal and posterior pelvic tilt. According to the authors, postural energy efficiency depends on the alignment of the spine and pelvis in the sagittal plane [34,35,36]. This phenomenon is particularly evident during the performance of motor tasks, which are commonly evaluated by analysing the sway of the center of gravity [37,38,39]. Furthermore, electromyography (EMG) studies have demonstrated that alterations in body posture result in asymmetrical loading of the lower limbs [40]. As postural dysfunction increases, the path traveled by the center of gravity becomes longer, indicating weakened compensatory responses [41]. According to Nault et al. [42], both the quality and magnitude of spinal deformity play a key role in determining spinal movement, with greater deviations involving the displacement of the centre of gravity in both the sagittal and frontal planes. Research has indicated that the characteristics of thoracic kyphosis play a pivotal role in this oscillation and the concomitant alteration in the tension of back extensor and calf muscles [40,42,43]. However, other studies have shown that alterations in balance parameters are associated with variations in the lumbar lordosis angle, thereby negating the influence of thoracic kyphosis angle [44]. Numerous studies have investigated methods for assessing posture and balance quality. Nevertheless, accurately evaluating the relationship between balance responses and posture types remains challenging, as does determining which specific postural components have the most significant influence on balance quality. It is evident that distinct posture types result in divergent balance parameters [22,40,44]. It has also been demonstrated that individuals exhibiting postural deviations from normative standards demonstrate reduced balance performance compared with those presenting optimal posture [26]. The literature also indicates that cognitive tasks, particularly those requiring effort as well as visual variability, have a significant impact on postural balance in adolescents with intellectual disabilities [45]. However, such relationships were not observed in the present study. No statistically significant differences in balance parameters were found among individuals with different posture types according to Dolphens and Frohner, or among individuals with different pelvic positions.

Study Limitation

The present study was conducted in a relatively large study group comprising 100 adults of both sexes. However, a limitation of the study was the unequal distribution of participants across the balanced, lordotic, and kyphotic posture groups. This limitation was particularly evident in the relatively small group of participants with kyphotic posture, a condition that was prevalent among healthy young adults. Future studies should aim to increase sample sizes to ensure a more balanced distribution of participants across all identified subgroups. The classification according to Frohner revealed that the sizes of the two groups were comparable. However, obtaining comprehensive information concerning the relationships between posture type, body structure and silhouette, balance, and their impact and load on the musculoskeletal system requires more complex and multidimensional studies, potentially involving more advanced measurement equipment. The results of the present study may serve as a basis for comparison with findings obtained in populations with impaired body statics.

5. Conclusions

The study showed that balance parameters and foot loading during standing did not differ significantly among the three posture types defined by Dolphens (balanced, kyphotic, and lordotic). Stabilometric and foot loading parameters, as well as pelvic tilt angles and angles of subsequent spinal segments, did not differ between the two posture types defined according to Frohner. Moreover, participants with different pelvic positions did not differ significantly as regards maintaining balance or foot loading.