Twenty healthy young people participated in this study. The characteristics of participants are shown in Table 1. The participants performed pulmonary function test in the resting or 30° trunk rotation in the sitting position. Respiratory variables (VC, IC, VT, ERV, IRV, FVC, FEV1.0, and FEV1.0%) and respiratory muscle strength variables (PImax and PEmax) were measured in each posture.
Table 1
Physiological characteristics of participants
|
All (n=20)
|
Male (n=9)
|
Female (n=11)
|
Age (year)
|
22 ±1
|
22 ± 1
|
22 ± 1
|
Height (cm)
|
163.5 ± 8.4
|
170.8 ± 5.8
|
157.5 ± 4.6***
|
Weight (kg)
|
57.4 ± 12.9
|
68.6 ± 11.1
|
48.3 ± 3.6***
|
BMI (kg/m2)
|
21.3 ± 3.4
|
23.5 ± 3.6
|
19.4 ± 1.5**
|
SMI (kg/m2)
|
6.7 ± 1.3
|
7.9 ± 0.8
|
5.6 ± 0.4***
|
Data are presented as mean ± standard deviations. BMI: body mass index SMI: skeletal muscle mass index. **: p<0.01, ***: p<0.001. |
The value of VC, IC, ERV, IRV, FVC, or FEV1.0 for males were significantly higher than that for females in both postures (Table 2).
Table 2
Differences in respiratory and respiratory muscle variables during the rest or rotational posture in sitting position between male and female
|
|
Male
|
Female
|
t-value
|
Male vs Female
|
VC
(L)
|
Rest
|
4.7 ±0.6
|
3.0 ± 0.4
|
7.0
|
p<0.001
|
Rotation
|
4.3 ± 0.7
|
2.7 ± 0.5
|
6.1
|
p<0.001
|
IC
(L)
|
Rest
|
2.6 ±0.4
|
1.7 ± 0.4
|
5.3
|
p<0.001
|
Rotation
|
2.6 ±0.4
|
1.7 ± 0.4
|
4.5
|
p<0.001
|
TV
(L)
|
Rest
|
0.8 ±0.3
|
0.7 ± 0.4
|
0.6
|
n.s.
|
Rotation
|
0.8 ± 0.3
|
0.7 ± 0.3
|
0.6
|
n.s.
|
ERV
(L)
|
Rest
|
2.0 ± 0.4
|
1.3 ± 0.4
|
4.2
|
p<0.001
|
Rotation
|
1.7±0.3
|
1.0 ± 0.3
|
4.8
|
p<0.001
|
IRV
(L)
|
Rest
|
1.8 ± 0.4
|
1.0 ± 0.3
|
5.5
|
p<0.001
|
Rotation
|
1.8 ± 0.4
|
1.0 ± 0.3
|
5.8
|
p<0.001
|
FVC
(L)
|
Rest
|
4.7 ± 0.6
|
3.1 ± 0.4
|
7.1
|
p<0.001
|
Rotation
|
4.4 ± 0.7
|
2.7 ± 0.5
|
6.4
|
p<0.001
|
FEV1.0
(L)
|
Rest
|
4.1 ± 0.5
|
2.8 ± 0.4
|
6.5
|
p<0.001
|
Rotation
|
3.8 ± 0.6
|
2.5 ± 0.5
|
5.9
|
p<0.001
|
FEV1.0%
(%)
|
Rest
|
87.2 ± 4.6
|
90.4 ± 4.7
|
1.5
|
n.s.
|
Rotation
|
87.1 ± 4.4
|
89.9 ± 4.6
|
1.4
|
n.s.
|
PImax
(cmH2O)
|
Rest
|
89.5 ± 32.1
|
65.6 ± 21.5
|
2.0
|
n.s.
|
Rotation
|
86.1 ± 28.9
|
59.4 ± 16.4
|
2.6
|
p<0.05
|
PEmax
(cmH2O)
|
Rest
|
101.5 ± 25.9
|
62.7 ± 14.8
|
4.2
|
p<0.01
|
Rotation
|
89.1 ± 29.0
|
58.5 ± 13.8
|
3.1
|
p<0.01
|
All data are presented as mean ± standard deviations.
VC: vital capacity, IC: inspiratory capacity, VT: tidal volume, ERV: expiratory reserve volume, IRV: inspiratory reserve volume, FVC: force vital capacity, FEV1.0: forces expiratory volume in one second, FEV1.0%: forces expiratory volume % in one second, PImax: maximal inspiratory pressure, and PEmax: maximal expiratory pressure. n.s.: not significant.
|
Figure 1 shows the results of the two-way ANOVA with repeated measures and post-hoc analysis. There was significant main effect of gender on FVC, FEV1.0, VC, ERV, PImax, and PEmax (FVC: F1, 18=45.8, p<0.001, VC: F1, 18=44.6, p<0.001, ERV: F1, 18=25.0, p<0.001, PImax: F1, 18=5.3, p<0.05, PEmax: F1, 18=13.6, p<0.01). In these variables, males showed greater value than females in rest posture and rotational posture.
There was significant main effect of posture on FVC, FEV1.0, VC, ERV, PImax, and PEmax (FVC: F1, 18=45.8, p<0.001, VC: F1, 18=44.6, p<0.001, ERV: F1, 18=25.0, p<0.001, PImax: F1, 18=7.3, p<0.05, PEmax: F1, 18=32.1, p<0.001). For males and females, the rotational posture significantly decreased these values.
A significant interaction between gender and posture was observed in PEmax (F1, 18=7.5, p<0.05). In PEmax, the rotational posture decreased the male value more in males than in females.