Effect of chest expansion resistance exercise and respiratory muscle stretching on respiratory function and gait endurance in patients with stroke

Abstract

Background

Limited chest expansion and asymmetry in the respiratory muscles after a stroke lead to poor ventilation and reduced physical performance.

Objectives

To determine the effect of chest expansion resistance exercise and respiratory muscle stretching on respiratory function and gait endurance in patients with stroke.

Methods

Thirty stroke patients were randomly assigned to a chest expansion resistance group (CERG), a respiratory muscle stretching group (RMSG), and a control group (CG). CERG and RMSG received chest expansion resistance and respiratory muscle stretching, respectively, 3 times a week for 8 weeks. Respiratory function, respiratory muscle strength, and gait endurance were measured before and after the intervention period.

Results

The experimental groups, CERG and RMSG, showed significant improvements in respiratory function variables (p < .05). For respiratory muscle strength variables, maximal inspiratory pressure (MIP) in the CERG and maximal expiratory pressure (MEP) in the RMSG showed significant changes compared to the CG (p < .05). Both CERG and RMSG also showed significant improvements in the 6MWT compared to the CG (p < .05).

Conclusion

Chest expansion resistance exercise would be a more effective method, while both chest expansion resistance exercise and respiratory muscle stretching are helpful in improving respiratory function and gait endurance.

Keywords

chest expansion resistance exercise respiratory muscle stretching respiratory function respiratory strength gait endurance

Introduction

Stroke is a cerebrovascular disease that causes long-term disability and places a great burden on patients by causing paralysis and impairment of sensory, motor, cognitive, language, visual perception, and swallowing functions (Bolognini et al., 2020; Geed et al., 2021). Although some degree of neurological recovery is possible after surviving a stroke, approximately 80% of hemiplegic patients experience hemiplegia and may have permanent disability (Demeco et al., 2023). It consumes inefficient energy due to trunk asymmetry and misalignment and causes difficulty in maintaining the center of gravity within the base of support, resulting in secondary gait disorders, balance control disorders, and daily living activities. Asymmetric movements in the trunk are associated with asymmetric activation of the respiratory muscles.

Partial or total weakness of the respiratory muscles on the paretic side has been observed in stroke patients, which appears to affect respiratory function due to limited expansion of the ribcage and poor postural control of the trunk (Britto et al., 2011; Lanini et al., 2003). The intercostal muscles, diaphragm, and abdominal muscles weakened by paralysis are activated asymmetrically, and the elasticity of the paralyzed diaphragm is reduced, resulting in insufficient ventilation, which negatively affects exercise performance and function (Kelly et al., 2003). In stroke patients, the maximum inspiratory pressure and maximum expiratory pressure are also lower than that of normal, and there is a large decrease in chest wall kinematics during normal breathing (Hsia, 1999; Teixeira-Salmela et al., 2005).

For symmetrical alignment and movement of the body, it is necessary to activate the paralyzed respiratory muscles and the immobilized rib cage movement. Respiratory training also helps stroke patients to increase muscle endurance, as well as respiratory strength and improve breathing ventilation (Lista-Paz et al., 2019; Wu et al., 2020). Chest expansion resistance exercise is a method of promoting the alignment and function of respiratory muscles by providing resistance to the sternum and ribs in accordance with the breathing rhythm, improving the mobility of the intercostal space and relaxing stiff connective tissues and muscles such as the pectoralis major and intercostal muscles (Dean & Frownfelter, 2014; Kido et al., 2013; Nair et al., 2021). A study by Kim, Shin, & Choi (2015) emphasized that chest expansion resistance exercise and diaphragm exercise through proprioceptive neuromuscular facilitation for stroke patients enhances thoracic movement, strengthens the respiratory muscles, and increases endurance.

As another method, respiratory muscle stretching has been proposed as an intervention that may reduce chest wall stiffness, consequently increasing its expansion and improving ventilation patterns in patients with chronic obstructive pulmonary disease (de Sa et al., 2017; Leelarungrayub et al., 2009; Minoguchi et al., 2002). In previous studies in which respiratory muscle stretching exercise in stroke and COPD patients exerted an effect on respiratory function and chest expansion, a significant change in the expiratory flow rate and peak cough flow rate after stretching was observed (de Sa et al., 2017; Rattes et al., 2018).

The risk of death due to respiratory complications from neuromuscular disease can no longer be overlooked, and the importance of respiratory rehabilitation is growing. Research on respiratory training for stroke is still insufficient compared to that for other diseases, such as cardiopulmonary diseases or spinal cord injury, which have direct respiratory problems.

Although research has demonstrated that respiratory interventions are effective in improving respiratory function in stroke patients, most of these studies have been limited to short-term interventions or specific populations and have not provided specific intervention methods for respiratory training (Cho et al., 2018; Tsui et al., 2023). In addition, many studies lacked clear, clinically applicable intervention methods (Brooks et al., 2001; Hodges et al., 2007). This study aims to address these limitations by evaluating the long-term effects of simple, clinically applicable interventions.

The purpose of this study is to provide evidence emphasizing the importance of respiratory interventions for stroke patients by comparing and analyzing the effects of clinically easy-to-apply chest expansion resistance exercises and respiratory muscle stretching on respiratory function, respiratory muscle strength, and gait endurance in stroke patients. The novelty of this research lies in the selection criteria of participants and long-term evaluation, distinguishing it from previous short-term studies. Furthermore, this study provides a comprehensive analysis of not only respiratory function but also respiratory muscle strength and gait endurance, offering direct clinical applicability. Through this, the study aims to propose new methods for the rehabilitation of stroke patients.

Methods

Participants

Thirty subjects diagnosed with stroke were recruited and randomly divided into three groups through a paper lottery: chest expansion resistance exercise group (CERG), respiratory muscle stretching group (RMSG), and control group (CG). The selection criteria were as follows: (1) diagnosis of stroke at least 3 months ago, (2) ability to walk independently or using an aid and walking under supervision for a minimum of 3 meters, (3) no cognitive impairment (scored at least 24 points on the Korean version of the Mini-Mental State Examination [K-MMSE]). The exclusion criteria were as follows: (1) with visual or auditory abnormalities, such as vestibular disease, cerebella disease, (2) participating in another experiment, (3) peripheral arterial disease with claudication, advanced congestive heart failure, unstable angina, uncontrolled hypertension (>190/110 mmHg). Prior to the study, those who understood the purpose of this study and who expressed their intention to participate were included in this study. This study was approved by the Institutional Bioethics Committee of Sunmoon University (SM-202101-001-2).

Experimental procedures

This study intended to proceed after screening for compliance with the selection criteria. During the recruitment process, one person refused to participate and was excluded, and the remaining 28 individuals participated in this study.

This study was single-blinded, and the subjects were randomly assigned to each group, 10 each to the CERG and RMSG, and 8 subjects to the CG, using the lottery method. All groups applied the conventional therapeutic exercise consisting of neurodevelopmental treatment, mat training, and gait training 5 times a week during the training period. Only subjects of the CERG and the RMSG performed additional respiratory exercises, chest expansion resistance exercise, and respiratory muscle stretching, respectively, 3 times a week for 8 weeks, for 15 minutes per session. All subjects underwent evaluations for respiratory function, respiratory muscle strength, trunk control ability, balance, and gait ability.

Clinical intervention

All subjects received basic therapeutic exercise consisting of joint motion range exercise, muscle strengthening, stretching, balance exercise, and walking exercise.

The chest expansion resistance exercise applied a method combining chest cage resistance and diaphragm resistance. Subjects were instructed to relax their body in a supine position, bending the knees to minimize the lumbar curve. The therapist placed their hands on the sternum, rib cage, and diaphragm in a sequential manner. The subject was requested to start with a full exhalation and instructed to “breathe in deeply” with gentle resistance applied to the sternum and ribs; depending on the resistance location, resistance was applied in the caudal and dorsal directions opposite to the sternum movement, and the medial and caudal direction opposite to the rib cage movement (Adler et al., 2014; Taussig & Landau, 2008). Subsequently, the diaphragmatic resistance was performed with the hand placed just below the lower rib cartilage during inhalation. The patients breathed in deeply against the manual resistance while maintaining the shoulder in a relaxed state, allowing only abdominal rise. After maximum inhalation, the subjects were requested to hold their breath and remain in that state for approximately 3 seconds. The intervention consisted of 10 repetitions for each resistance position, for a total of 15 minutes.

The respiratory muscle stretching based on passive and hold-relax stretching techniques was applied to upper trapezius, sternocleidomastoid, scalene, and pectoralis major bilaterally in the supine position, and to the intercostal muscles in a lateral side-lying position (Rattes et al., 2018; Rehman et al., 2020). Each muscle was stretched passively up to the full range of motion and the position was held with isometric contractions for 5 seconds slightly below the range, followed by 5 seconds of relaxation, 2 sets of 5 repetitions for each muscle, with an interval of 1 minute between the sets. The intercostal muscles were stretched in a lateral side-lying position during inspiration, with bilateral rib assessment conducted during expiration.

If the subjects felt fatigued or complained of dizziness, difficulty breathing, headache, etc., they were advised to stop exercising or take a break.

Outcome measures

Spirometry (Pony FX, COSMED, Italy) was used to assess respiratory function and respiratory muscle strength. We evaluated the forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁), the ratio of forced expiratory volume for 1 second to forced vital capacity (FEV₁/FVC), peak expiratory flow (PEF), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP). For accurate measurement, the evaluations were carried out after sufficient explanation and demonstrations. The measurement was performed until a result with high reproducibility was repeated three times, and the average value was used.

The 10MWT evaluates the mobility of the subject. It is commonly used to evaluate the walking speed of patients with neurological impairment. A total of 14 m was walked at a comfortable speed; the walking time was measured for 10 m in the walking passage, excluding 2 m at both the beginning and the end from the measurement considering acceleration and deceleration. It was measured twice, and the average value was calculated.

The 6MWT was used to evaluate walking endurance. In the 6MWT, a square of 30 m (10 wide by 5 vertical) was marked with a tape on the floor, such that the participant could recognize the walking area. The participant was asked to walk as quickly as possible for 6 minutes on a 30 m pedestrian walkway. The walking speed and the resting time can be adjusted to suit individual abilities. After starting at the departure signal, only the remaining time was given to eliminate the motivational error during walking, and only the phrases (‘You are doing well’, ‘Go on’, ‘One minute left’ after 5 minutes) allowed in the instructions were used. The total distance walked in meters (m) and the number of cycles walked were recorded.

Statistical analysis

For data processing, the statistical package of social sciences (SPSS) software for Windows (version 22.0; IBM Corp., Armonk, NY, USA) was used. All data were represented as mean and standard deviation (SD), and significance level was set at p,< .05. Normality of the data for the general characteristics and variables was tested using the Shapiro–Wilk test. As a result of the variable normality test, there were several factors that did not follow the normal distribution; therefore, non-parametric statistics were used. The Wilcoxon signed-rank test was used to analyze the pre- and post-test data for each group. The Kruskal–Wallis test was used to compare the three groups; additionally, the Mann–Whitney U test was used for post-hoc follow-up test.

Results

The general characteristics of the three groups are shown in Table 1. Thirty patients with hemiplegic stroke participated in this study. Among the general characteristics of the subjects, there were no significant differences between groups with respect to age, height, weight, onset duration, and smoking duration; however, there were significant differences between groups in MMSE-K scores. The evaluation results for respiratory function, respiratory muscle strength, and gait endurance are described in Table 2.

Table 1.

General characteristics of subjects (N = 30).

	CERG (n = 10)	RMSG (n = 10)	CG (n = 10)	P value
Gender
Male/Female (%)	8/2	8/2	6/4	–
Disease
Infarction/Hemorrhage (%)	5/5	8/2	5/5	–
Hemiplegia side
Right/Left (%)	5/5	3/7	6/4	–
Onset duration (month)	10.16±5.84	14.66±4.96	12.85±4.37	.256
Age (years)	50.83±5.60	53.16±11.07	58.85±5.63	.114
Height (cm)	170.33±10.38	165.83±6.82	166.57±8.48	.856
Weight (kg)	72.00±20.30	69.33±17.82	63.82±11.19	.905
MMSE-K (point)	28.66±5.84	28.00±4.96	25.42±1.39	.012*
Smoker/Non-smoker	6/4	4/6	5/5	–
Smoking duration (years)	23.66±14.73	19.83±11.19	20.69±15.62	.768

Note. MMSE-K = mini mental state examination Korean, *p < .05. Values are expressed as mean±standard deviation.

Table 2.

Results of respiratory function, respiratory muscle strength, and gait endurance.

		CERG	RMSG	CG	P value
FVC (L)	T0	2.42±0.43	2.42±.81	2.03±.42	.251
	T1	2.98±0.38	2.82±.79	2.21±.37	.006^**
	P value	.005^**	.005^**	.066
	T1-T0	.56±.30	.40±.37	.17±.25	.028*
FEV₁ (L)	T0	2.11±0.41	2.02±.61	1.80±.43	.322
	T1	2.89±0.32	2.53±.73	1.91±.46	.003^**
	P value	.005^**	.016*	.799
	T1-T0	.77±.29	.50±.48	.10±.37	.009^**
FEV₁/FVC (%)	T0	87.47±9.68	86.22±17.40	89.01±10.91	.887
	T1	97.61±10.30	89.91±12.89	85.87±23.56	.118
	P value	.037*	.646	.721
	T1-T0	10.13±12.81	3.69±17.39	–1.13±24.86	.348
PEF (L/s)	T0	3.84±0.99	3.79±1.36	2.99±.68	.073
	T1	4.83±1.64	4.51±1.06	3.33±.94	.034*
	P value	.009^**	.022*	.074
	T1-T0	.98±1.03	.72±.77	.33±.58	.186
MIP (cmH₂O)	T0	33.50±10.55	29.30±7.28	27.70±12.34	.355
	T1	53.10±12.73	33.90±9.03	28.70±12.69	.021*
	P value	.005^**	.262	.671
	T1-T0	19.60±12.04	4.60±10.26	1.00±3.99	.001^**
MEP (cmH₂O)	T0	42.30±11.81	46.80±9.06	36.50±11.86	.091
	T1	57.40±19.44	61.30±15.14	39.50±14.27	.021*
	P value	.092	.059	.074
	T1-T0	15.10±23.28	14.50±16.57	3.00±5.18	.316
10MWT (s)	T0	20.19±6.54	24.73±13.28	29.81±13.77	.335
	T1	18.55±5.76	19.18±10.09	26.12±10.24	.226
	P value	.009^**	.005^**	.013*
	T1-T0	–1.64±1.23	–5.55±4.91	–3.69±3.76	.140
6MWT (m)	T0	160.81±43.82	155.11±61.54	154.57±51.62	.879
	T1	208.04±55.87	195.23±76.85	170.50±52.72	.503
	P value	.005^**	.005^**	.013*
	T1-T0	47.23±16.23	40.11±19.84	18.43±8.58	.001^**

T0, baseline data; T1, data after 8 weeks of intervention; T1-T0, the difference before and after intervention; *p < .05; ^**p < .01.

Respiratory function

FVC, FEV₁, FEV₁/FVC and PEF for CERG, and FVC, FEV₁ and PEF for RMSG significantly increased after 8weeks (p < .05). After intervention, significant differences were found in FVC, FEV₁, and PEF values between CERG and CG, and in FEV₁ and PEF values between RMSG and CG (p < .05). CERG showed significant differences in the changes of FVC and FEV₁ compared to the CG (p < .05).

Respiratory muscle strength

MIP for CERG showed a significant improvement after 8weeks compared to RMSG and the CG (p < .05). A significant difference was found in the MIP changes between CERG and RMSG, and between CERG and CG (p < .05). MEP value for RMSG showed a significant difference compared to the CG (p < .05).

Gait endurance

After intervention, 10MWT durations decreased and 6MWT distances statistically increased in all groups (p < .05), with no significant difference observed between the three groups (p > .05). A significant difference was found in the 6MWT changes between CERG and RMSG experimental groups and CG (p < .05).

Discussion

This study investigated the effects of chest expansion resistance training—where the therapist applies manual resistance to the sternum and bilateral rib cage to enhance chest mobility—and respiratory muscle stretching on respiratory function, respiratory muscle strength, and gait endurance. The research provides a comprehensive analysis of the long-term effects and practical applicability of these interventions. By considering participant characteristics, the study enhances the generalizability of the results and offers a thorough evaluation of the sustained benefits of these interventions.

Previous studies have shown that a restrictive pulmonary pattern occurs in patients with stroke, probably due to the limited respiratory movements that make the chest wall, and abdominals expand (Menezes et al., 2016). After 8weeks, FVC, FEV₁, and PEF values significantly increased in the experimental groups, CERG and RMSG. At 8 weeks, significant differences were observed in FVC, FEV₁, and PEF between CERG and CG.

The increases in FVC, FEV₁, and PEF are attributable to the fact that when the subjects in CERG were inhaling and exhaling, the therapist promoted the activities of the diaphragm and other accessory respiratory muscles around the sternum and rib cage. Subsequently, when the subject exhaled, the movement of the chest wall was increased as much as possible, and the lower part of that was gathered inward to perform auxiliary movements; therefore, it is considered that pulmonary ventilation was induced as much as possible. Similarly, Song & Park (2015) applied chest resistance exercises and expansion to patients with stroke and reported that there were significant changes in the FVC and FEV₁.

Wada et al. (2016) evaluated the effect of aerobic training combined with respiratory muscle stretching in COPD patients. They confirmed that the respiratory muscle effort required to achieve the same lung volume decreased in the group that received aerobic training combined with respiratory muscle stretching (Wada et al., 2016). Similarly, Rattes et al. (2018), focusing on patients with stroke, observed increases in minute ventilation, mean inspiratory flow and mean expiratory flow, and tidal volume after respiratory muscle stretching. They mentioned that the hemiplegic side benefited the most from respiratory muscle stretching.

In our study, RMSG showed significant differences in FEV₁ and PEF values compared to CG. Persistent muscle immobilization due to stroke paralysis leads to a decrease in the number of sarcomeres and an increase in connective tissue deposition, altering contractile proteins and mitochondrial metabolism. This results in muscle shortening and restricted thoracic movement. Therefore, it is considered that stretching of the respiratory muscles performed in RMSG could increase the functional length of the muscle and facilitate the interaction between actin and myosin, thereby improving the chest wall compliance by relaxing the muscles involved in chest cage movements.

Since the maximum inspiratory pressure and the maximum expiratory pressure cannot directly measure the muscle strength of the respiratory muscles, they are evaluated by indirectly measuring the maximum static pressures during inhalation and exhalation. Maximum static pressure provides a more accurate indication of respiratory muscle weakness.

There was a significant change in MIP in the CERG compared to that in the RMSG and CG. The chest expansion resistance exercise concentrates on thoracic movement because the therapist applies manual resistance to the chest directly, and it is effective in enhancing the strength of the respiratory muscles and the thoracic range of motion (Areas et al., 2013). The manual resistance respiratory exercise of the therapist was effective in increasing peak inspiratory pressure and maximal expiratory pressure and strengthening respiratory muscle strength (Areas et al., 2013). These results suggest that, by providing a load to the respiratory muscles, repeated breathing training and active resistance training resulted in improvement of muscle strength and coordination. In our study, chest extension resistance exercise applied to CERG was performed during the inspiration, and it is believed to have had a positive effect on improving inspiratory muscle strength.

There was no significant improvement in MEP across all groups, however, RMSG was significantly higher in MEP value compared to the CG after intervention. Previous studies reported an immediate enhancement in the respiratory pattern following respiratory muscle stretching in COPD patients, attributed to afferent information from respiratory muscles (de Sa et al., 2017; Ito et al., 1999). It has been suggested that stretching of the inspiratory muscle around the neck and chest wall, including the intercostal muscles, affects chest wall stiffness and chest wall receptors, thereby changing ventilator capacity and chest compliance (Ali et al., 2014; Miyahara et al., 2000). In addition, inspiratory muscles relaxed by the stretching are associated with a decrease in muscle tone (Marek et al., 2005). Thus, it is believed that the decrease in muscle tension during maximal expiration did not interfere with myoelectric activity.

Aydogan et al. (2022) noted that 6 weeks of inspiratory muscle training for stroke showed improvements in the MIP and MEP as well as TIS, BBS, and 6MWT. Significant differences between groups were found in TIS, PEF, and MIP; however, there were no significant differences in balance or gait. Other studies reported that respiratory muscle training showed significant differences in balance, gait, and walking performance, and a significant increase compared to those in the control group (Lee & Kim, 2018; Vaz et al., 2021). In this study, significant improvements in 10MWT and 6MWT were observed in all three groups, with no significant differences between the groups. This suggests that improvement in physical function was evident, as all groups participated in hospital-based rehabilitation training for the duration of 8 weeks, including the control group.

Regarding the change in 6MWT value, and CERG and RMSG showed significant differences compared to CG, of which CERG showed the largest change, decreasing by 47.23 meters after intervention. There is a close relationship between respiratory function and walking endurance in patients with stroke (Lanini et al., 2003). Aydogan et al. (2022) showed that inspiratory muscle training in addition to neurological physiotherapy and rehabilitation program improved trunk control and 6MWT in stroke patients. Weiner et al. (2003) reported that there was a correlation between the increase in inspiratory muscle function and the increase in the 6MWT value. Montemezzo et al. (2014) reported that the improvement in respiratory muscle strength increases the aerobic capacity and ventilation capacity, thereby reducing fatigue during movement. Ultimately, respiratory intervention applied to both CERG and RMSG had a positive impact on improving respiratory function, respiratory muscle strength, and enhancing gait endurance, consistent with the findings of previous studies.

Conclusion

The purpose of this study was to investigate the effects of chest expansion resistance and respiratory muscle stretching on respiratory function, respiratory strength, and gait endurance in patients with stroke. Both chest expansion resistance exercise and respiratory muscle stretching enhanced respiratory function in patients with stroke. Chest expansion resistance exercise showed greater benefits in enhancing FVC, FEV₁, PEF, and MIP. Additionally, gait endurance, measured by the 6MWT, improved significantly in both intervention groups compared to the control group. Thus, chest expansion resistance exercise is particularly recommended for improving respiratory function and physical performance in hemiplegic stroke patients.

Footnotes

Acknowledgments

The authors would like to thank all participants for their time and dedication to this study. We also extend our gratitude to the staff of the Department of Physical Therapy and the Digital Healthcare Institute at Sunmoon University for their support and assistance throughout the research process.

Ethical considerations

This study was conducted in accordance with the ethical principles of the Declaration of Helsinki. Ethical approval was obtained from the Institutional Bioethics Committee of Sunmoon University (SM-202101-001-2).

Informed consent

All individual participants provided written informed consent prior to their inclusion in the study. Participants were provided with detailed information about the study procedures, potential risks, and benefits, and they voluntarily agreed to participate.

Funding

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (RS-2023-00275755).

Conflict of interest

The authors declare that they have no conflicts of interest.

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