Effectiveness of water-based Liuzijue exercise on respiratory muscle strength and peripheral skeletal muscle function in patients with COPD

Figures & data

Table 1 Baseline characteristics of participants

Characteristics	CG (n=16)	LG (n=15)	WG (n=14)	p-value
Age (years)	66±8	65±8	65±11	0.96
Sex (male/female)	12/4	12/3	9/5	0.62
BMI (kg/m^2)	24±3	23±4	23±3	0.73
FEV1%pred	59±17	55±17	59±22	0.77
FEV1/FVC (%)	60±8	60±18	62±14	0.86
Years of COPD	12±4	13±4	12±4	0.79
COPD stage				0.63
Grade I	2 (12.50)	2 (13.33)	3 (21.43)
Grade II	9 (56.25)	10 (66.67)	9 (64.29)
Grade III	3 (18.75)	3 (20.00)	2 (14.28)
Grade IV	2 (12.50)	0	0

Notes: Data are expressed as mean ± SD or n (%). One-way analysis of variance was used to compare the age, BMI, FEV₁%pred, and FEV₁/FVC among groups, and the chi-square test was used to compare sex and COPD stage among groups. The significance level was set at p<0.05.

Abbreviations: %pred, percentage of predicted values; BMI, body mass index; CG, control group; FEV₁, forced expiratory volume in the first second; FVC, forced vital capacity; LG, land-based Liuzijue exercise group; WG, water-based Liuzijue exercise group.

Figure 1 Study flow diagram.

Abbreviations: CG, control group; LG, land-based Liuzijue exercise group; WG, water-based Liuzijue exercise group.

Table 2 Comparisons of group changes (%) in pulmonary function and respiratory muscle strength

Variables	CG (n=16)			LG (n=15)			WG (n=14)			p-value
	Pre	Post	Δchanges (%)	Pre	Post	Δchanges (%)	Pre	Post	Δchanges (%)
FEV1%pred	59±17	57±14	−0.03±0.02	55±17	57±16	0.05±0.04	59±22	60±22	0.05±0.06	0.177
FEV1/FVC (%)	60±7.57	57±14	−0.03±0.06	60±18	57±13	0±0.05	62±14	60±15	−0.03±0.02	0.911
PImax (kPa)	4.23±1.11	4.24±1.05	0.01±0.02	4.01±1.4	4.46±1.18*	0.15±0.05##	4.03±1.34	5.68±1.51*	0.49±0.11##	<0.001
PEmax (kPa)	5.05±1.43	4.93±1.44*	−0.02±0.01	4.9±1.17	6.57±1.73**	0.35±0.05##	4.84±1.88	6.61±2.72*	0.75±0.43##	<0.001

Notes: Pre and post data are expressed as mean ± SD, Δchanges (%) = ([post − pre]/pre) ×100, and expressed as mean ±SEM. Within groups was compared by the paired-sample t-test, one-way analysis of variance was used to compare the changes of FEV₁/FVC between groups, and the nonparametric Kruskal-Wallis test was used to compare the changes of respiratory muscle strength and FEV₁%pred between groups.

* p<0.05, comparisons are significant within groups.

** p<0.01, comparisons are significant within groups.

## p<0.01, group changes (%) comparison are significant between the control group and the intervention group.

Abbreviations: %pred, percentage of predicted values; CG, control group; FEV₁, forced expiratory volume in the first second; FVC, forced vital capacity; LG, land-based Liuzijue exercise group; PEmax, maximal expiratory pressure; PImax, maximal inspiratory pressure; post, postintervention; pre, preintervention; WG, water-based Liuzijue exercise group.

Figure 2 Pulmonary function before and after the 3-month intervention.

Notes: Data are expressed as mean ± SD. No differences were observed between the groups at baseline and after the intervention. Within-groups comparison was made by the paired-sample t-test.

Abbreviations: %pred, percentage of predicted values; CG, control group; FEV₁, forced expiratory volume in the first second; FVC, forced vital capacity; LG, land-based Liuzijue exercise group; post, postintervention; pre, preintervention; WG, water-based Liuzijue exercise group.

Figure 3 Changes of pulmonary function and respiratory muscle strength after the 3-month intervention.

Notes: Delta changes (%) = ([post − pre]/pre) ×100, and they are expressed as mean ± SEM. Between-group comparisons used the one-way analysis of variance or the nonparametric Kruskal–Wallis test and are expressed as a p-value. The level of significance was set at p<0.05, and ^##p<0.01 means it was significant when compared to the control group.

Abbreviations: %pred, percentage of predicted values; CG, control group; FEV₁, forced expiratory volume in the first second; FVC, forced vital capacity; LG, land-based Liuzijue exercise group; PEmax, maximal expiratory pressure; PImax, maximal inspiratory pressure; WG, water-based Liuzijue exercise group.

Figure 4 Respiratory muscle strength before and after the 3-month intervention.

*p<0.05, comparisons were significant within groups. **p<0.01, comparisons were significant within groups.

Notes: Data are expressed as mean ± SD. No differences were observed between the groups at baseline. Within-groups comparison was made by the paired-sample t-test.
Abbreviations: CG, control group; LG, land-based Liuzijue exercise group; PEmax, maximal expiratory pressure; PImax, maximal inspiratory pressure; post, postintervention; pre, preintervention; WG, water-based Liuzijue exercise group.

Table 3 Comparisons of group changes (%) in muscle function of elbow joints

Variables	CG (n=16)			LG (n=15)			WG (n=14)			p-value
	Pre	Post	Δchanges (%)	Pre	Post	Δchanges (%)	Pre	Post	Δchanges (%)
Extensor PT (N m)	38.75±7.93	38.31±7.89	−0.01±0.01	39.73±8.64	40.07±8.17	0.01±0.01	39.3±14.33	38.7±14.23	0.02±0.06	0.109
Flexor PT (N m)	39.69±7.28	39.19±7.89	−0.01±0.02	39.53±7.07	39.4±6.54	0±0.01	36.6±12.65	36.8±10.67	0.04±0.05	0.438
Extensor PT/BW (N m/kg)	0.61±0.11	0.59±0.1	−0.01±0.01	0.62±0.15	0.63±0.15	0.01±0.01	0.61±0.17	0.6±0.15	0.02±0.06	0.109
Flexor PT/BW (N m/kg)	0.62±0.1	0.61±0.09	−0.01±0.02	0.62±0.14	0.62±0.15	0±0.01	0.57±0.15	0.58±0.13	0.04±0.05	0.438
Extensor TW (J)	378.55±88.98	381.13±92.59	0.01±0.01	365.47±104.57	403.64±76.42**	0.15±0.05	328.04±108.16	400.5±168.76*	0.22±0.09##	0.004
Flexor TW (J)	350.55±81.39	340.36±78.92	−0.03±0.02	348.64±91.36	387.14±80.21**	0.14±0.04#	301.54±113.75	451.71±160.72**	0.62±0.16##	<0.001
Extensor ER	0.65±0.11	0.62±0.13*	−0.06±0.02	0.65±0.13	0.69±0.1	0.09±0.05#	0.65±0.08	0.71±0.14	0.1±0.05##	0.002
Flexor ER	0.67±0.09	0.67±0.1*	−0.01±0.01	0.71±0.12	0.72±0.13	0.03±0.02	0.71±0.14	0.72±0.11	0.04±0.05	0.11

Notes: Pre and post data are expressed as mean ± SD, Δchanges (%) = ([post − pre]/pre) ×100, and they are expressed as mean ±SEM. Within-groups comparison was made by the paired-sample t-test and the nonparametric Kruskal–Wallis test was used to compare the changes of elbow joints muscle function between groups.

* p<0.05, comparisons were significant within groups.

** p<0.01, comparisons were significant within groups.

# p<0.05, group changes (%) comparison was significant between the control group and the intervention group.

## p<0.01, group changes (%) comparison was significant between the control group and the intervention group.

Abbreviations: BW, body weight; CG, control group; ER, endurance ratio; LG, land-based Liuzijue exercise group; post, postintervention; pre, preintervention; PT, peak torque; TW, total work; WG, water-based Liuzijue exercise group.

Figure 5 Muscle function of elbow joints before and after the 3-month intervention.

Notes: (A–D) Within-groups comparisons in CG, LG, and WG of the elbow extensor and flexor PT and PT/BW to reflect the changes of muscle strength after intervention; (E–H) Within-groups comparisons in CG, LG, and WG of the elbow extensor and flexor TW and ER to reflect the changes of muscle endurance after intervention. Data are expressed as mean ± SD. No differences were observed between the groups at baseline. Within-groups comparisons were made with the paired-sample t-test. *p<0.05, comparisons were significant within groups, **p<0.01, comparisons were significant within groups.
Abbreviations: BW, body weight; CG, control group; ER, endurance ratio; LG, land-based Liuzijue exercise group; post, postintervention; pre, preintervention; PT, peak torque; TW, total work; WG, water-based Liuzijue exercise group.

Table 4 Comparisons of group changes (%) in muscle function of knee joints

Variables	CG (n=16)			LG (n=15)			WG (n=14)			p-value
	Pre	Post	Δchanges (%)	Pre	Post	Δchanges (%)	Pre	Post	Δchanges (%)
Extensor PT (N m)	77.01±22.46	76.74±21.73	0±0.01	76.62±21.86	77.98±21.33*	0.02±0.01	71.55±33.42	82.92±33.00*	0.19±0.07#	0.041
Flexor PT (N m)	48.31±19.84	47.50±19.39*	−0.02±0.01	47.03±20.76	47.08±18.49	0.01±0.01	45.47±20.99	47.66±16.89	0.08±0.04#	0.024
Extensor PT/BW (N m/kg)	1.19±0.30	1.19±0.28	0±0.01	1.18±0.23	1.20±0.22*	0.02±0.01	1.09±0.32	1.27±0.34*	0.19±0.04#	0.041
Flexor PT/BW (N m/kg)	0.74±0.25	0.73±0.25	−0.02±0.01	0.71±0.23	0.72±0.20	0.01±0.01	0.69±0.22	0.73±0.17	0.09±0.04#	0.028
Extensor TW (J)	816.46±326.02	817.64±305.62	0.02±0.02	705.89±308.43	745.98±283.58**	0.09±0.03	712.14±516.47	983.58±563.44**	0.56±0.18##	0.002
Flexor TW (J)	643.64±240.87	589.78±230*	−0.08±0.03	579.53±238.67	593.47±232.71	0.03±0.02#	532.63±304.65	731.09±312.8**	0.51±0.15##	<0.001
Extensor ER	0.56±0.18	0.55±0.15	0.01±0.04	0.57±0.16	0.57±0.15	0.01±0.03	0.56±0.20	0.60±0.20	0.16±0.11#	0.027
Flexor ER	0.63±0.12	0.59±0.13**	−0.06±0.02	0.62±0.12	0.62±0.11	0±0.01	0.59±0.17	0.62±0.12	0.09±0.06#	0.02

Notes: Pre and post data are expressed as mean ± SD, Δchanges (%) = ([post − pre]/pre) ×100, and they are expressed as mean ±SEM. Within-group comparisons were made by the paired-sample t-test, one-way analysis of variance was used to compare the changes of extensor ER between groups and post hoc multiple comparisons were performed using Bonferroni test, and the nonparametric Kruskal–Wallis test was used to compare others between groups.

* p<0.05, comparisons are significant within groups.

** p<0.01, comparisons are significant within groups.

# p<0.05, group changes (%) comparison was significant between the control group and the intervention group.

## p<0.01, group changes (%) comparison was significant between the control group and the intervention group.

Abbreviations: BW, body weight; CG, control group; ER, endurance ratio; LG, land-based Liuzijue exercise group; post, postintervention; pre, preintervention; PT, peak torque; TW, total work; WG, water-based Liuzijue exercise group.

Figure 6 Muscle function of knee joints before and after the 3-month intervention.

Notes: (A–D) Within-groups comparisons in CG, LG, and WG of the knee extensor and flexor PT and PT/BW to reflect the changes of muscle strength after intervention; (E–H) Within-groups comparisons in CG, LG, and WG of the knee extensor and flexor TW and ER to reflect the changes of muscle endurance after intervention. Data are expressed as mean ± SD. No differences were observed between the groups at baseline. Within-groups comparisons were made with the paired-sample t-test. *p<0.05, comparisons were significant within groups. **p<0.01, comparisons were significant within groups.

Abbreviations: BW, body weight; CG, control group; ER, endurance ratio; LG, land-based Liuzijue exercise group; post, postintervention; pre, preintervention; PT, peak torque; TW, total work; WG, water-based Liuzijue exercise group.

Figure 7 Changes of elbow and knee joints of muscle function after 3-month intervention. Muscle function of elbow joints are shown in A and B, while knee joints are shown in C and D.

Notes: Delta changes (%) = ([post − pre]/pre) ×100, and they are expressed as mean ± SEM. Between-group comparisons used the one-way analysis of variance or the nonparametric Kruskal–Wallis test and are expressed as a p-value. The level of significance was set at p<0.05, and ^#p<0.05 and ^##p<0.01 mean it was significant when compared to the CG.
Abbreviations: BW, body weight; CG, control group; ER, endurance ratio; LG, land-based Liuzijue exercise group; post, postintervention; pre, preintervention; PT, peak torque; TW, total work; WG, water-based Liuzijue exercise group.