The effect of deep tissue massage on respiratory parameters in healthy subjects—A non-randomised pilot study

Abstract

Background

Deep tissue massage (DTM), based on deep palpation and elimination of fascia restrictions, can reduce symptoms resulting from fascial disorders. The goal of this study was the analysis of the DTM effect on respiratory parameters in healthy people.

Material and methods

The study involved a group of 40 people divided into two subgroups. The experimental group underwent a single DTM session. Classic massage was performed in the control group. Before and after treatment the chest circumference and oxygen saturation were measured and a spirometry test was performed.

Results

The chest expandability significantly increased in both groups with greater effect in DTM group. Vital capacity and saturation, significantly increased in the experimental group. No significant changes in dynamic parameters were noticed in the control group, while FVC slightly decreased in the experimental group.

Conclusions

In this study, deep tissue massage appeared to improve chest expendability and vital capacity with simultaneous decrease of FVC in healthy subjects. Further studies are needed to specify the effect of DTM on the respiratory system.

1. Introduction

Deep tissue massage (DTM) was created as a synthesis of many years of experience of therapists and teachers like Ida Rolf, John Smith, Thomas Myers or Art Riggs. There are many definitions of DTM described by Riggs as a technique based on understanding of the layers of body tissues and patient, precise work with them which is aimed at the release of restrictions in the myofascial apparatus. That allows to achieve quick results noticeable both on the structural and functional level [1,2].

In DTM all techniques are performed without a lubricant, as it would impede deep palpation. DTM mainly include elongating techniques, stretching, deep pressure-especially on the muscle attachments, „filleting” (tissue compartment separation), and also soft tissues and joints release. It is also common to combine these techniques with patients' active movement [2,3]. Techniques involving hard elements such as elbows, fists or finger joints are performed using the body weight of the therapist with maximum relaxation of the patient. The direction of pressure to the tissues should not exceed an angle of 45°, which reduces the likelihood of patients' discomfort as well as allows for the appropriate speed and depth of technique [1]. The effectiveness of the therapy is based mainly on the therapist's experience in identifying the places for intervention and selecting the appropriate tools. Contraindications to this type of therapy are mainly the local and generalized inflammation, fever, risk of hemorrhage, skin damage and diseases, infections, advanced atherosclerosis, thrombosis or phlebitis, aneurysms, damages of muscles in acute phase, bones fragility, osteomyelitis, disorders of the vegetative system, non-terminal cancers, numbness or paresthesia of neurological origin, syringomyelia, high joint instability, hypersensitivity to touch or advanced diabetes [[1], [2], [3], [4]].

Fascia is a three-dimensional connective tissue network that runs continuously throughout the body. It connects small parts of body, such as individual muscle fibers, with large sets of muscles to form a collective whole. The quality of tissue within the fascia system varies in terms of density or function, so three types of fascia can be distinguished: superficial, deep, and muscle-related fascial layers [[5], [6], [7]]. The muscles are contained within the deep fascia, which is soft and elastic thus it allows the muscle fibers effective elongation and contraction. It also fills the spaces between the muscles, creating muscle compartments while in places where it is built in a more organized way, it creates ligaments and tendons [8].

Myofascial restriction, may occur as a result of, among others, inflammation, trauma or postural stress. Compensatory changes within the tissues may cause adhesions between structures that should function separately, reducing their ability to move freely relative to each other what may lead to functional limitations and/or pain. The action of DTM as a method of elimination of myofascial restrictions is supposed to be based on the elimination of these adhesions by realigning the layers of connective tissue [[9], [10], [11]]. According to some authors this process can be described by mechanically changing the density of the ground substance, which enables the separation of collagen fibers, while elastin allows the released tissues to return to their original shape and mobility [4,8,12].

In the available literature there are reports on the effectiveness of DTM used in various diseases, however, there is a shortage of studies that assess the impact of MTG on individual systems of the human body, particularly in healthy people, for whom it can be a form of wellness or relaxation as well as a part of sport training program. Due to the above described effects of DTM, and the fact that myofascial restrictions may also occur in people without diagnosed diseases, we assumed that its use in such people may significantly affect various functional parameters including those of the respiratory system. The above-mentioned restrictions can also occur in the respiratory muscles and those affecting the mechanics of the chest. It can therefore be assumed that the use of DTM within the myofascial apparatus of the chest will have a positive effect on its mobility and the efficiency of the respiratory muscles. Thus, respiratory parameters should improve, primarily those related to the ability of expanding the chest, such as the vital capacity of the lungs. The aim of the study was to check whether a single DTM session performed in the thoracic area could significantly affect the respiratory parameters in young healthy subjects.

2. Material and methods

2.1. Design

This study was a two-arm non-randomized trial, with two intervention groups and was registered at ClinicalTrials.gov (ID: NCT05093179). The experiment was carried out from February to march 2019 in the Jagiellonian University Medical College. All participants were informed about the details and purpose of the project, instructed on voluntary participation and the possibility of resignation at any stage of its duration, and gave their voluntary written consent to participate in the study. Ultimately two groups of people–20 persons each-of similar somatic features meeting the inclusion criteria were recruited separately (without randomization). The first group was designated as experimental that underwent a single DTM procedure and the second one as control in which classic massage was administered. Participants in both groups underwent outcome measurements twice - before and after the treatment procedure. All measurements were performed by different person than therapists that administered the treatment in each group. The study was conducted following the Helsinki Convention and approved by The Bioethics Committee of Jagiellonian University Medical College in Cracow (opinion no. 1072.6120.7.2019).

2.2. Participants

A healthy, physically active people of both sexes living in the city of Cracow and meeting inclusion criteria were recruited to the study by the authors personally and through social media. An original questionnaire was completed in the presence of the examiner in order to collect the participants characteristics data. Questions about past diseases, previous surgical procedures or injuries, currently taken medications or the level of physical activity were asked to check the inclusion/exclusion criteria.

2.3. Inclusion criteria

Age between 18 and 25 yrs.

• 1.Physical activity of minimum 30 min duration, at least 3 times a week.
• 2.No chest injuries.
• 3.No contraindications for DTM/classic massage.
• 4.No serious diseases of the respiratory and/or cardiovascular systems.
• 5.No tobacco products smoking (incl.e-smoking).
• 6.No posture defects that could affect the chest mobility.

2.4. Exclusion criteria

• 1.Contraindications to DTM/classic massage of the chest.
• 2.Occurrence of serious diseases of the respiratory/cardiovascular system now or in the past.
• 3.Lack of or low physical activity (<30 min min 3 times per week).
• 4.Tobacco smoking (incl.e-smoking).
• 5.Chest injuries.
• 6.Posture defects that may affect the chest mobility.

2.5. Outcome measures

The chest circumference was measured with a measuring tape, wrapped horizontally around the chest at the level of the xiphoid process. The subject was standing with feet hip-width apart, arms hanging along the body. At the command, the subject would take a maximum breathe in (first measurement) and exhale to the maximum for the next (second measurement). Obtained values were recorded with an accuracy of 0.5 cm.

Testing blood oxygen saturation (SpO₂) was performed in a sitting position with a digital pulseoximeter CMS50D (CONTEC CO. Ltd.). The device was put on the second finger of the left hand each time. The highest value displayed by the pulseoximeter within 30 s was recorded with an accuracy of 1%.

The vital capacity (VC) of the lungs was assessed with spirotest (Riester, mod. 5260). The subject stood with legs hip-width apart. For each measurement, disposable cardboard mouthpieces were used. The examined person held the device vertically with both hands. At the examiner's command, the subject took in as much air as possible, then tightly bit the mouthpiece with his mouth, and with all of their strength, exhaled air into the device for as long as possible. The subject had only 1 attempt-measured values were recorded with an accuracy of 50 ml. Subsequently, a dynamic spirometry test was performed, assessing the following measurements: peak expiratory flow (PEF), peak inspiratory flow (PIF), forced vital capacity (FVC), maximum expiratory flow (MEF), forced expiratory volume in 1 s (FEV1) and maximum voluntary ventilation (MVV). The test was performed with PNEUMO® spirometer and PNEUMO 2005 software (abcMED). The subject was sitting with his legs on the floor-hip joint flexed at an angle of 70°-90° and carried out the following command: „Breathe calmly. On my command, breathe in as much as possible, as quickly as possible, as intensively as possible, and while at the top of the inhalation, without waiting, breathe out as hard and as long as possible “. This cycle was performed at least 3 times obtaining 3 measurements according to the standard ERSATS 2005. When testing MVV, the following command was given: „Breathe calmly. On my command, inhale and exhale as quickly and as deeply as possible for 15 s until you hear the ‘stop’ command. The set of the above tests was repeated in both groups immediately after the DTM/classic massage.

2.6. DTM procedure

In our study DTM was performed by the therapist with 5 years' experience in its clinical use. All performed techniques, although might slightly differ between some authors, stayed in accordance with the rules of performing the DTM [1,2]. Depending on type and size of the subject's body the entire procedure took about 35–45 min. The subject's positions were changed depending on the specificity of used techniques.

First, the subject lies on his back, feet close to the buttocks. The following techniques were used:

Shifting the rectus abdominis m., Stretching of the fascia within the costal arches, trigger points compression (30–60 s).

Next, the subject was still lying on his back, with lower limbs extended, the upper limbs raised above the head. The following techniques were used:

Stretching of the chest fascia, superficially with forearm or fingertips on intercostal muscles, “filleting” the pectoral muscles, “hook and stretch” with the proximal phalanges of the fingers 2–4 and the forearm.

“filleting” between the pectoral muscles and the deltoids, Then, the subject was placed in a side lying position. The following techniques were used:

Releasing the lateral edge of the scapula using the fingers and stretching the tissues, Releasing the medial edge of the scapula using the fingers and the weight of the patient, “hook and stretch” of the trapezius muscle, Subsequently, the patient took a prone position.

Stretching of the levator scapulae and supraspinatus muscles using the fist, forearm and elbow were performed.

2.7. Classic massage procedure

The subject was lying supine on the table, with a roller placed under the knee joints, the upper limbs along the body. The massage was performed with moderate force by a masseur with 4 years of massage experience. The entire procedure took about 15–20 min. In order to relax the abdominal wall, a roller was placed under the knee joints - the upper limbs along the body. The following sequence of techniques was used in standard way and patterns (the longitudinal and transverse strands and in the intercostal spaces - excluding the breast in women) [13]: effleurage, friction, petrissage, pressures, tapotement and vibrations. The massage ended with stroking.

2.8. Statistical analysis

The analysis was conducted using Statistica 13.3 (StatSoft Inc.) software. The Shapiro-Wilk test was used to check the normality of the variables’ distribution. To analyze the differences between the results obtained in each group separately before and after the procedure the t-student test for coupled variables or Wilcoxon test was used. In the comparison of changes of parameters in both groups, the t-student test for independent variables or the Mann-Whitney U test was used. The clinical significance of the results and the effect size were calculated on the basis of distribution-based method (d Cohen). The changes of assessed parameters were considered clinically significant when equals to 0.2 standard deviation for “small” effect size, to 0.5 standard deviations for “moderate” and >0.8 for “large” effect size [14]. The results were considered statistically significant with p < 0.05.

3. Results

The flow of participants through the experiment shows Fig. 1. The gender ratio in both groups was the same-12 women and 8 men. The somatic characteristics of the participants in both groups was shown in Table 1.

Fig. 1.

Flow of participants through the experiment.

Table 1.

Comparison of descriptive statistics of somatic parameters in both groups.

Parameter	Experimental Group				p	Control Group
	Mean	SD	Min	Max		Mean	SD	Min	Max
Age [yrs]	22.5	1.93	19	25	0.0636	21.5	1.10	20	24
Height [cm]	170	8.9	155	182	0.2716	174	10.0	160	197
Body mass [kg]	69.34	11.92	54	97	0.6494	71.25	14.33	50	105
BMI [kg/cm2]	23.82	2.6	19.59	29.94	0.6566	23.45	2.63	19.03	28.13

Legend: BMI–body mass index, Max–maximum value, Min–minimum value, p–level of significance, SD - standard deviation.

The homogeneity test showed statistically significant differences between investigated groups in terms of baseline results of VC (p = 0,013) and chest circumference in expiration (p = 0,015) while no significant differences were stated for other parameters.

After treatment, the mean chest circumference measurement in the experimental group increased in inspiration by 1.07 cm while in expiration increased by 0.65 cm. The mean VC increased by 240 ml. The mean value of saturation increased by 1.4%. For all parameters, the difference was highly statistically significant however effect size exceeded the value of 0.2 only for VC and blood saturation (Table 2).

Table 2.

Changes in chest circumference, blood saturation and vital capacity in experimental group.

Parameter		Mean	SD	Difference	p	ES
chest circumference	before	98.48	6.90	1.07	0.000089	0.16
INSPIRATION [cm]	after	99.54	7.10
chest circumference	before	95.90	6.88	0.65	0.003346	0.09
EXPIRATION [cm]	after	96.55	7.05
SpO2 [%]	before	96.40	1.10	1.40	0.000293	1.27
	after	97.80	0.70
VC [ccm]	before	3817.50	721.16	240.0	0.000089	0.33
	after	4057.50	679.45

Legend: p–significance level, SD−standard deviation, ES - effect size, SpO_2–blood saturation, VC–vital capacity.

In the control group, the mean chest circumference in inspiration and expiration increased significantly in both cases. The mean VC increased by 75 mL (p > 0.05). The mean value of saturation remained unchanged. No parameter showed the effect size above the value of 0.2 in this group (Table 3).

Table 3.

Changes in chest circumference, blood saturation and vital capacity in control group.

Parameter		Mean	SD	Difference	p	ES
chest circumference-inspiration [cm]	before	95.05	8.55	0.30	0.0277	0.04
	after	95.35	8.41
chest circumference-expiration [cm]	before	90.40	6.74	0.30	0.0277	0.05
	after	90.70	6.58
SpO2 [%]	before	96.80	1.67	0.00	1.0000	0
	after	96.80	2.14
VC [ccm]	before	4640.00	1217.59	75.00	0.3139	0.06
	after	4715.00	1186.45

Legend: p–significance level, SD−standard deviation, ES- effect size, SpO₂–blood saturation, VC–vital capacity.

The comparison of changes in the parameters obtained in both groups showed statistically significant differences in the change of the chest circumference during inspiration, saturation and VC. The difference in chest circumference during expiration did not differ significantly between both groups (Table 4).

Table 4.

Comparison of change of assessed parameters after the intervention in both groups.

Variable Change	Control Group				p	Experimental Group
	Mean	SD	Min	Max		Mean	SD	Min	Max
chest circumference-inspiration [cm]	0.30	0.47	0.00	1.00	0.0003	1.07	0.71	0.50	3.50
chest circumference-expiration [cm]	0.30	0.47	0.00	1.00	0.2733	0.65	0.93	0.00	3.00
SpO2 [%]	0.00	2.94	−6.00	5.00	0.0494	1.40	0.94	0.00	3.00
VC [ccm]	75.00	263.33	−400.00	700.00	0.0008	240.00	110.74	100.00	550.00

Legend: p–significance level, SD−standard deviation, SpO2–blood saturation, VC–vital capacity.

The comparison of the values of spirometry parameters before and after DTM in both groups showed a statistically significant change in the FVC parameter only in the experimental group (−0.18 l, p = 0.0328 with small effect size equal to 0.2) - the values of the other parameters showed no statistically significant differences (p > 0.05) with effect sizes <0,2 (Table 5, Table 6).

Table 5.

Changes of spirometry parameters in experimental group.

Parameter		Mean	SD	Difference	p	ES
MVV [l/min]	before	139.35	25.68	−3.13	0.3317	−0.12
	after	136.22	40.67
FEV1 [l]	before	3.80	0.59	−0.04	0.2575	−0.07
	after	3.75	0.60
FVC [l]	before	4.69	0.91	−0.18	0.0328	−0.20
	after	4.51	0.75
PEF [l/s]	before	7.05	1.67	0.09	0.5639	0.05
	after	7.14	1.79
MEF75 [l/s]	before	6.34	1.43	0.20	0.4330	0.14
	after	6.54	1.63
MEF50 [l/s]	before	4.64	1.07	−0.15	0.3443	−0.14
	after	4.49	1.17
MEF25 [l/s]	before	2.28	0.85	−0.10	0.6951	−0.12
	after	2.18	0.62
PIF [l/s]	before	6.49	2.16	0.36	0.7194	0.17
	after	6.85	1.61

Legend: FEV1- forced expiratory volume in 1 s, FVC–forced vital capacity, Max–maximum value, MEF-maximal expiratory flow, Min–minimum value, MVV-maximum voluntary volume, p-level of significance, PEF- peak expiratory flow, PIF- peak inspiratory flow, SD-standard devi-ation, ES – effect size.

Table 6.

Changes of spirometry parameters in control group.

Parameter		Mean	SD	Difference	p	ES
MVV [l/min]	before	147.93	40.08	2.38	0.4457	0.06
	after	150.31	35.35
FEV1 [l]	before	4.04	1.20	0.05	0.2549	0.04
	after	4.09	1.02
FVC [l]	before	4.35	1.37	0.26	0.0669	0.19
	after	4.61	1.15
PEF [l/s]	before	6.11	2.48	0.17	0.2959	0.07
	after	6.29	2.67
MEF75 [l/s]	before	5.62	2.39	0.16	0.5016	0.07
	after	5.78	2.54
MEF50 [l/s]	before	4.87	1.47	−0.09	0.7263	−0.06
	after	4.78	1.73
MEF25 [l/s]	before	3.37	1.04	−0.25	0.1804	−0,24
	after	3.12	1.01
PIF [l/s]	before	5.32	1.94	−0.23	0.3289	−0.12
	after	5.09	1.70

Legend: FEV1- forced expiratory volume in 1 s, FVC–forced vital capacity, Max–maximum value, MEF-maximal expiratory flow, Min–minimum value, MVV-maximum voluntary volume, p-level of significance, PEF- peak expiratory flow, PIF- peak inspiratory flow, SD - standard deviation, ES – effect size.

The comparison of the changes in dynamic respiratory parameters obtained after the procedure in both groups showed significant differences only in FVC (0.26 vs −0.18). The differences of other parameters were not statistically significant (Table 7).

Table 7.

Comparison of the changes in spirometry parameters obtained after treatment in both groups.

Variable Change	Control Group				p	Experimental Group
	Mean	SD	Min	Max		Mean	SD	Min	Max
MVV [l/min]	2.38	13.67	−19.18	35.73	0.9461	−3.13	26.26	−105.26	21.44
FEV1 [l]	0.05	0.56	−1.78	0.91	0.2915	−0.04	0.52	−1.10	1.71
FVC [l]	0.26	0.59	−0.74	1.24	0.0087	−0.18	0.31	−0.95	0.20
PEF [l/s]	0.17	1.49	−4.50	2.96	0.6849	0.09	1.45	−2.84	3.92
MEF75 [l/s]	0.16	1.60	−4.82	3.45	0.9569	0.20	1.39	−2.82	4.04
MEF50 [l/s]	−0.09	1.15	−2.20	2.20	0.8817	−0.15	1.17	−3.25	3.21
MEF25 [l/s]	−0.25	0.79	−1.43	0.91	0.4249	−0.10	0.62	−2.15	0.90
PIF [l/s]	−0.23	1.04	−1.84	2.12	0.1298	0.36	1.15	−1.46	2.57

Legend: FEV1- forced expiratory volume in 1 s, FVC–forced vital capacity, Max–maximum value, MEF-maximal expiratory flow, Min–minimum value, MVV-maximum voluntary volume, p-level of significance, PEF- peak expiratory flow, PIF- peak inspiratory flow, SD - standard deviation.

4. Discussion

Our study seems to be the first one assessing the impact of DTM techniques on the respiratory system in healthy subjects. We confirmed the statistically significant effect of DTM techniques on the expandability of the chest however with effect size below the accepted limit. These results are comparable with those obtained by other authors. The influence of DTM on the flexibility and mobility of soft tissues has been studied by Forman, et al., who assessed the effect of deep stripping massage (DSM) in combination with eccentric training on the length of posterior group of thigh muscles in healthy people [15]. The control group consisted of people who received only DSM. In this group, the authors found a significant increase in the flexibility of treated muscles by 6.3% after application 15 deep longitudinal stripping massage strokes. Interestingly, a significantly greater improvement in flexibility (10.7%) was found in the experimental group by combining DSM with eccentric training. Romanowski et al. compared the use of 10 DTM sessions, and the same number of therapeutic massage in patients with ankylosing spondylitis [3]. They found a significant improvement in mobility in the sagittal plane and improved chest expansion in both groups however without significant differences between them what may suggest smaller effect of DTM in non-healthy subjects.

In our study, an increase in VC was observed in both groups, however, it was significant only in the experimental group with ES equal to 0.33 what places this result between “small” and “moderate” effect size. The influence of DTM on this parameter has not been studied so far, therefore there are no exact comparative data. Improved expandability of the chest should increase the capacitive parameters of the respiratory system. This claim seems to be supported by research of Putt et al., who found that stretching techniques performed within the chest increase the range of motion and VC in patients with COPD [16]. Nekooee et al. found that the respiratory parameters in children with asthma improved after massage [17]. They obtained a significant increase of FVC after a 20 min of classic massage daily performed for 1 month. In turn, the meta-analysis on the impact of massage therapy on pulmonary functions in children with asthma conducted by Xu et al. showed no significant changes of FVC in the analyzed reports [18]. In our study, this parameter slightly increased in the control group and slightly decreased–possibly due to deeper relaxation of respiratory muscles or bronchoconstriction due to activation of the parasympathetic system–in experimental group. Despite the statistical significance of those changes, their clinical significance seems to be questionable and requires further studies.

The influence of massage on respiratory parameters was also investigated by Abdel Fattah and Hamdy who stated that in children with asthma, forced expiratory volume in the first second (FEV1) increased significantly [19]. In their study, patients were subjected to 20 min massage sessions daily for 5 weeks. On the other hand, own research on a group of healthy people did not show a significant change in this parameter in both groups-perhaps because of the single treatment, as opposed to several sessions of which effects could add up and result in significant change.

Our study also showed a significant increase in saturation (p = 0.0000) immediately after the procedure in the study group with large effect size. The measurement error of the device is up to 2%, so the value of this parameter could be questioned. On the other hand, Challand and Locatelli assessing the effect of relaxing the fascia within the mediastinum on the autonomic system, found that as a result of the therapy there were changes in the frequency of heartbeats, which may have been caused by the stimulation of the vagus nerve [20]. Thus, the increase of the VC and the heartbeat rate could affect the level of blood saturation. Increased saturation was also found in the studies by Hatefi et al., who assessed the effect of massage on various parameters of emergency units patients [21]. The average increase in saturation in the experimental group subjected to massage was 2,67%. It is important that patients were subjected to classic full body massage (45 min session) and that they were intensive care patients with lower baseline levels of saturation. In the light of these facts further research are needed to determine the effect of DTM on blood saturation.

Our analysis shows that a single session of classic massage performed on chest does not have a significant effect on the selected respiratory parameters in healthy subjects. The fact of a slight increase in parameters such as the chest circumference on the inspiration, the expiration and VC-however statistically significant compared to the test before the procedure (p = 0.0277)-we considered clinically insignificant as the effect size was placed markedly below accepted limit. We also did not note any significant changes in the dynamic spirometry test. To sum up, a single session of classic massage of the chest-although it causes slight changes in the circumference of the chest-has no clinically significant effect on the selected respiratory parameters. This may confirm the accuracy of the assumption that classic massage, of moderate intensity, can be used as a control treatment in relation to other types of soft tissue therapy. This claim could be confirmed by the results obtained by Thomson et al., who assessed the effect of a single session of classic massage treatment in comparison with the superficial heat treatment on the flexibility of the calf muscles in healthy people [22]. The authors, who passively assessed the stiffness and range of motion of the ankle joint, found no significant differences between the groups, which may confirm the lack of a significant effect of a single classic massage treatment on the passive mechanical characteristics of muscles.

The mechanisms of DTM action have not yet been precisely defined. Information published so far on the mechanisms of operation of techniques similar to DTM (i.e., myofascial release, swedish massage) mentioned an increase in the activity of the parasympathetic system, and an increase in the activity of the vagus nerve due to stimulation of the receptors (baro- and mechanoreceptors) present in the skin. This resulted in a decrease of blood pressure, heart rate and cortisol level, as a result of which among many others a pain reduction and relaxation [[23], [24], [25], [26], [27], [28]]. A similar effect in the case of DTM was found by Kaye et al., who assessed an effect of DTM of 45–60 min duration on blood pressure in a group of 263 volunteers [29]. They found a reduction in systolic and diastolic blood pressure, with values at the border of statistical significance (p < 0.06 and < 0.04 respectively) and a highly statistically significant reduction in the heart rate (p < 0.0003). The authors emphasize however, the need for further research in this area. In addition to affecting the autonomic nervous system, possible mechanisms of DTM activity may also relate to the direct impact of a mechanical factor on the fascia [4,28,30]. Due to the lack of studies directly related to the action of DTM, it is necessary to conduct high-quality randomized studies to assess the impact of DTM on individual functional parameters.

Our study has several limitations that should be considered in a future research. The most important are is a relatively small sample size what that limits the generalization of the findings. Further observations on a larger group of respondents are necessary, taking into account the division into subgroups according to age, profession and possibly other factors (i.e. level of physical activity) that may affect the functionality of the respiratory system. Another limitation is the lack of placebo-controlled group. The use of Swedish massage, although with minor effects, produced noticeable changes in respiratory parameters in healthy persons. Next limitation is the lack of randomization in the allocation of participants to both groups which resulted in some differences of baseline outcomes. These differences, although of minor character, made both groups inhomogeneous in terms of some parameters thus affecting in some extent the reliability of some analyses. Stress of the respondents was also found as an important factor during the study. Most of them performed spirometry tests for the first time in their lives and despite the full explanation of the procedure, they felt insecure. Usually, the spirometry measurement after the massage treatment achieved slightly better values - it could also be caused by performing the test again, and thus becoming familiar with the test procedures so this factor should certainly be taken into account in further studies.

The results of analysis of effect sizes showed “small” effect sizes or lack of clinical importance in most of assessed parameters. In our opinion these results are very relative. For example the 240 ml change of VC would be not clinically important for people with average physical performance but for highly trained athletes or for persons with obstructive diseases it would probably be a significant difference. On the other hand this value was the mean of results obtained for all participants while in some of them it reached values over 500 ml. This fact additionally support the importance of future studies on larger groups of people to obtain more reliable data.

The last but not least limitation is that in our study, the changes were determined immediately after the therapy, therefore it is necessary to check the duration of the effects of the treatment in long-term observation. Despite the above mentioned limitations and the pilot character of our study, its results allow us to believe that DTM could have a positive impact on many conditions, both in healthy and unhealthy persons. As it may improve respiratory parameters in healthy people it could be used as a part of sports training procedures - especially in endurance disciplines - as well as a part of wellness program. In non-healthy persons it seems to be a promising tool in the management of patients with reduced vital capacity of the lungs. Thus we consider this study as a good starting point for future research on the action of DTM, its effect on particular systems of human body and its use in clinical practice. This will allow for a better understanding of how DTM works and to establish a strategy for its use in various clinical circumstances.

5. Conclusions

The results of this study showed that the deep tissue massage performed within the chest area in young, healthy people affect the ability of the chest to expand, increase the vital capacity and slightly decrease the forced vital capacity. The values of other parameters did not change significantly. As this was the pilot study, further studies are needed to determine the details of the impact of deep tissue massage on the respiratory system.

Author contribution statement

Bartosz Trybulec: Conceived and designed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Macul Bartosz: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data.

Kościńska Karolina: Performed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data.

Nawrot-Porąbka Katarzyna; Jagielski Paweł: Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data.

Barłowska Marta: Contributed reagents, materials, analysis tools or data; Wrote the paper.

Data availability statement

Data will be made available on request.

Declaration of interest's statement

The authors declare no conflict of interest.

Appendix A. Supplementary data

The following is the supplementary data related to this article: