2. The age-related changes in the pelvic angles during sitting

The first section investigated the relationship between age and the maximum pelvic anteversion and retroversion angles, as well as the associated pelvic range of motion, which is measured based on the knee movement in the sitting position [44]. The pelvic range of motion was defined as the difference between the maximum pelvic anteversion and retroversion angles. The hypothesis of the present study was that pelvic range of motion would be affected by aging.

The participants included 132 healthy volunteers (female, n = 74; male, n = 58) of 20–79 years of age (Table 1). The participants were recruited from a university, two workplaces, and the community near the university. The participants were free from neurological and orthopedic impairments. After the experimental protocol was explained to all of the participants, they gave their informed consent.

All measurements were taken with the participants seated on a chair with a 50 cm · 50 cm seat face. The height of the seat face was 65 cm from the floor to allow the free movement of the knee joints. The participants sat on the chair. The front edge of the seating face was aligned with the point 66% along the length of the thigh from the greater trochanter.

The pelvic angles were measured based on the sacral inclination angle [46]. An inclinometer with a resolution of 1 was used to measure the pelvic angles. The pelvic tilt angle was defined as the angle between the longitudinal axis through the midline of the dorsal sacral surface and the anterior horizontal line (Figure 1).

The subjects were instructed to maintain the same anteroposterior shoulder position throughout the movements of pelvic inclination to avoid anteroposterior movement of the trunk. The


<sup>a</sup> Significant difference from 20 to 29 years of age.

<sup>b</sup> Significant difference from 30 to 39 years of age.

<sup>c</sup> Significant difference from 40 to 49 years of age.

<sup>d</sup> Significant difference from 50 to 59 years of age.

Table 1. The mean and standard deviation of the pelvic angles in each age group [44].

2. The age-related changes in the pelvic angles during sitting

by aging.

44 Clinical Physical Therapy

Age group n

20–29 years

30–39 years

40–49 years

50–59 years

60–69 years

70–79 years

gave their informed consent.

the anterior horizontal line (Figure 1).

angle (˚)

<sup>a</sup> Significant difference from 20 to 29 years of age. <sup>b</sup> Significant difference from 30 to 39 years of age. <sup>c</sup> Significant difference from 40 to 49 years of age. <sup>d</sup> Significant difference from 50 to 59 years of age.

Table 1. The mean and standard deviation of the pelvic angles in each age group [44].

n = 48

n = 13

n = 13

n = 23

n = 19

n = 16

Maximum pelvic anteversion

The first section investigated the relationship between age and the maximum pelvic anteversion and retroversion angles, as well as the associated pelvic range of motion, which is measured based on the knee movement in the sitting position [44]. The pelvic range of motion was defined as the difference between the maximum pelvic anteversion and retroversion angles. The hypothesis of the present study was that pelvic range of motion would be affected

The participants included 132 healthy volunteers (female, n = 74; male, n = 58) of 20–79 years of age (Table 1). The participants were recruited from a university, two workplaces, and the community near the university. The participants were free from neurological and orthopedic impairments. After the experimental protocol was explained to all of the participants, they

All measurements were taken with the participants seated on a chair with a 50 cm · 50 cm seat face. The height of the seat face was 65 cm from the floor to allow the free movement of the knee joints. The participants sat on the chair. The front edge of the seating face was aligned

The pelvic angles were measured based on the sacral inclination angle [46]. An inclinometer with a resolution of 1 was used to measure the pelvic angles. The pelvic tilt angle was defined as the angle between the longitudinal axis through the midline of the dorsal sacral surface and

The subjects were instructed to maintain the same anteroposterior shoulder position throughout the movements of pelvic inclination to avoid anteroposterior movement of the trunk. The

angle (˚)

84.53.4 123.1 6.1 38.7 6.0

87.84.1 125.7 6.8 37.6 9.2

90.15.4a 124.1 8.9 34.0 8.7

88.84.6a 118.2 9.8 29.4 8.4a,b

92.66.5a,b 117.1 8.7<sup>b</sup> 24.3 6.3a,b,c

9.39 4.0a,b,d 117.8 9.3 23.8 8.6a,b,c

Maximum pelvic retroversion

Pelvic range of motion

(˚)

with the point 66% along the length of the thigh from the greater trochanter.

Figure 1. A schematic illustration of the procedure for measuring the pelvic inclination angle: (A) the pelvic retroversion angle, (B) the pelvic anteversion angle [44].

instruction to the subjects was, "Please maintain your shoulder position during pelvic movement." Participants assumed alternating maximum pelvic anteversion and retroversion positions five times. The maximum and minimum angles were excluded, and the mean of the three remaining values was calculated. The pelvic range of motion was defined as the difference between the average maximum pelvic anteversion and retroversion angles.

The maximum pelvic anteversion angle, maximum pelvic retroversion angle, and the range of pelvic motion were significantly affected by aging (Table 1).

The maximum pelvic anteversion angles in participants of 40–49, 50–59, 60–69, and 70–79 years of age were significantly smaller than those in participants of 20–29 years of age. The maximum pelvic anteversion angles in participants of 60–69 and 70–79 years of age were significantly smaller than those in participants of 30–39 years of age, and the maximum pelvic anteversion angles in participants of 70–79 years of age were significantly smaller than those in participants of 50–59 years of age (Table 1).

With regard to the maximum pelvic retroversion angle, none of the age groups showed a significant difference in comparison to the 20–29 year age group. The maximum pelvic retroversion angle in the participants of 60–69 years of age was significantly smaller than that in the participants of 30–39 years of age (Table 1).

The pelvic ranges of motion in participants of 50–59, 60–69, and 70–79 years of age were significantly smaller in comparison to participants of 20–29 and 30–39 years of age. Furthermore, the pelvic range of motion of participants of 60–69 and 70–79 years of age was significantly smaller than that in participants of 40–49 years of age (Table 1).

The relationships between these variables and age were approximated using linear regression equations (Figure 2). These results indicate that pelvic mobility in the sitting position is affected by aging. There was a significant correlation between age and the maximum pelvic anteversion angle (r = 0.61, p < 0.001), the maximum pelvic retroversion angle (r = 0.29, p < 0.05), and the range of pelvic motion (r = 0.63, p < 0.001) (Figure 2).

Hamstring tension probably had an insignificant effect on pelvic mobility in this dataset, especially on the anterior tilt, because the knees could move freely during pelvic movement. The hip flexion angle during maximum pelvic anteversion was 87 and the extension angle during maximum retroversion was 57 in participants of 70–79 years of age. Thus, the pelvic mobility in the present study did not seem to be affected by hamstring muscle tension or hip joint mobility. The pelvic mobility measured in this study was in line with the results of previous studies on lumbar spine mobility, which reported strong correlations between pelvic tilt or the sacral tilt angle, and the lumbar spine lordosis angle in the sitting position [5, 46, 47]. In addition, the pelvic mobility in the sitting position is larger than that in the standing position [6]. Kuo et al. reported that there was a significant correlation between lumbar spine

Figure 2. The correlations between age and the maximum pelvic anteversion angle (black circles), the maximum pelvic retroversion angle (white squares), and the pelvic range of motion (black triangles) [44].

mobility and the pelvic tilt angle (r = 0.67) in the sitting position [5]. Thus, changes in the maximum pelvic anteversion and retroversion angles that occur with aging might be directly affected by the changes in lumbar spine mobility that occur with aging [11]. When sitting, the angle between the lumbar spine and the pelvis is reduced when leaning forward, especially in elderly individuals. It is considered that thoracic kyphosis becomes more pronounced and that the thoracic and the lumbar spines almost act as one segment to compensate for this reduced lumbar mobility [5].

The pelvic ranges of motion in participants of 50–59, 60–69, and 70–79 years of age were significantly smaller in comparison to participants of 20–29 and 30–39 years of age. Furthermore, the pelvic range of motion of participants of 60–69 and 70–79 years of age was signifi-

The relationships between these variables and age were approximated using linear regression equations (Figure 2). These results indicate that pelvic mobility in the sitting position is affected by aging. There was a significant correlation between age and the maximum pelvic anteversion angle (r = 0.61, p < 0.001), the maximum pelvic retroversion angle (r = 0.29, p < 0.05), and the

Hamstring tension probably had an insignificant effect on pelvic mobility in this dataset, especially on the anterior tilt, because the knees could move freely during pelvic movement. The hip flexion angle during maximum pelvic anteversion was 87 and the extension angle during maximum retroversion was 57 in participants of 70–79 years of age. Thus, the pelvic mobility in the present study did not seem to be affected by hamstring muscle tension or hip joint mobility. The pelvic mobility measured in this study was in line with the results of previous studies on lumbar spine mobility, which reported strong correlations between pelvic tilt or the sacral tilt angle, and the lumbar spine lordosis angle in the sitting position [5, 46, 47]. In addition, the pelvic mobility in the sitting position is larger than that in the standing position [6]. Kuo et al. reported that there was a significant correlation between lumbar spine

Figure 2. The correlations between age and the maximum pelvic anteversion angle (black circles), the maximum pelvic

retroversion angle (white squares), and the pelvic range of motion (black triangles) [44].

cantly smaller than that in participants of 40–49 years of age (Table 1).

range of pelvic motion (r = 0.63, p < 0.001) (Figure 2).

46 Clinical Physical Therapy

However, due to the aging-related shortening of the hamstring muscles, the maximum pelvic anteversion angle may be more restricted when performing this movement without the free mobility of the knees.

The pelvic range of movement was approximately 40 in participants of 20–29 years of age and approximately 24 in participants of 60–69 and 70–79 years of age. The rate of pelvic mobility limitation that occurred with aging in this study (approximately 30%) was larger than that previously reported for hip extension (approximately 20%), which is considered to be the joint in the lower extremities that is most limited by aging [48]. Thus, sagittal plane pelvic mobility may be an important factor that is associated with mobility limitation during the sit-to-stand movement in elderly adults.
