The effects of diaphragm release on sleep quality: a pilot feasibility study

Abstract

Background

Poor sleep quality is a common health concern with wide-ranging consequences. Manual diaphragm release, by improving diaphragmatic function and autonomic balance, may help enhance sleep quality. This pilot feasibility study aimed to explore the preliminary effects of diaphragm release on sleep quality in healthy individuals.

Methods

35 participants were included in the study. The Pittsburgh Sleep Quality Index (PSQI) and Fitbit smartband were utilized to evaluate individuals’ sleep quality. The diaphragm release technique was administered over three sessions, with two days of rest in between each session.

Results

Following the intervention, increases in sleep duration and sleep score were observed as per Fitbit measurements (p < 0.05). Post-intervention, statistically significant changes were found in sleep latency, sleep duration, sleep disturbance subscales, and the total score of the PSQI (p < 0.05).

Conclusions

As a preliminary investigation, this pilot study suggests that diaphragm release may be a feasible and safe intervention to enhance sleep quality. Further randomized controlled trials using gold-standard sleep assessments are needed to confirm these findings.

Clinicaltrials.Gov ID

NCT05762913 (Date: 10/03/2023).

Background

Sleep health is a critical determinant of overall well-being, and insufficient or poor-quality sleep has been associated with cardiovascular disease, metabolic disorders, impaired cognitive performance, and reduced quality of life [1]. In the long term, inadequate sleep quality has been linked to serious health conditions such as diabetes, cardiovascular disease, obesity, depression, anxiety, and stroke [2]. Multiple factors, including environmental, physiological, psychological, behavioral, and physical influences, can negatively affect sleep. Importantly, poor sleep quality is a widespread issue that impacts individuals across all age groups, from otherwise healthy populations to those living with chronic illnesses [1].

Respiration is a fundamental aspect of life [3]. As the primary respiratory muscle, the diaphragm plays a crucial role in breathing and physiological regulation [4]. However, its functions extend beyond respiration, as the diaphragm also contributes to vocalisation and swallowing, alongside its primary respiratory function [3]. The motion of the diaphragm during breathing influences the sympathetic and parasympathetic nervous systems and motor nerve activities [5].

Dysfunction of the diaphragm can disrupt physiological equilibrium and the interplay between body systems, leading to impaired breathing patterns [6]. This dysfunction is associated with various disorders, including respiratory insufficiency, exercise intolerance, and sleep disturbance [7]. The parasympathetic nervous system predominantly regulates sleep, with the vagus nerve playing a vital role in its control [8]. Since the phrenic nerve, responsible for innervating the diaphragm and facilitating its functions, connects with the vagus nerve [9], releasing the diaphragm can potentially increase parasympathetic tone and deepen breathing, thus improving sleep quality. Although direct evidence for manual diaphragm release is lacking, it can be hypothesized that improving diaphragmatic function may exert similar effects to slow deep breathing, which has been shown to reset autonomic balance by inhibiting sympathetic activity and enhancing parasympathetic activation [10]. Importantly, previous studies have also demonstrated that diaphragm release and stretching techniques can improve respiratory function and thoracic mobility by reducing tension on the diaphragm, including increases in maximal respiratory pressure and forced vital capacity [11, 12]. Through these pathways, interventions targeting the diaphragm may positively influence both physiological and psychological aspects of sleep regulation.

Diaphragm release or stretching techniques have been shown to improve lung function and circulation by reducing tension on the diaphragm [13]. However, there is limited evidence in the literature regarding the effects of these techniques. González-Álvarez et al. reported improvements in respiratory functions following the application of diaphragm stretching techniques in healthy individuals, emphasising increases in maximum respiratory pressure, forced vital capacity, and forced expiratory volume in the first second [11]. In another study, González-Álvarez et al. examined the effects of diaphragm stretching on posterior chain muscle kinematics, reporting improved thoracic and spinal mobility in healthy individuals [12].

To the best of our knowledge, no study has investigated the effect of diaphragm release on sleep quality in healthy individuals. Therefore, this pilot study aims to explore the preliminary effects and feasibility of diaphragm release on sleep quality in healthy individuals.

Methods

The study included individuals between the ages of 18 and 65 with no chronic diseases or psychological disorders. Exclusion criteria encompassed individuals with neurological, psychiatric, or cognitive disorders. The study sample comprised 35 participants, consisting of both students and academic staff from Tokat Gaziosmanpaşa University. Recruitment was conducted through voluntary announcements, and no financial compensation was provided for participation. According to the post hoc power analysis based on the PSQI, the statistical power of the study was calculated as 94%, assuming a Cohen’s d effect size of 0.546, an alpha level of 0.05, and a total sample size of 35. The flow diagram depicting participant selection is presented in Fig. 1.

Fig. 1.

Flow diagram

Data collection occurred between August 2023 and March 2024, following approval from the Tokat Gaziosmanpaşa University Ethics Committee. The clinical trial registration number of the study is NCT05762913 (Date: 10/03/2023). The study’s procedures were carried out in full compliance with the ethical guidelines of the Helsinki Declaration. Informed consent was obtained from all participants.

Outcome measures

The Pittsburgh Sleep Quality Index (PSQI) and Fitbit smartband were utilised to evaluate individuals’ sleep quality. The diaphragm release technique was administered over three sessions, with two days of rest between each session. Measurements were repeated after the completion of the intervention. The evaluations and interventions were conducted in the clinical setting of the Faculty of Health Sciences at Tokat Gaziosmanpaşa University. Participants wore the Fitbit device at home, including during sleep, for three consecutive days before and after the intervention.

The Pittsburgh sleep quality index

Sleep quality was assessed with the PSQI, which includes 19 self-rated items grouped into seven components (subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction). Five additional bed-partner/roommate items are available but are not scored. Each component is scored 0–3, yielding a global score of 0–21, with higher scores indicating poorer sleep quality; a global score >5 indicates poor sleep quality [14]. The Turkish version of the PSQI has also been validated, demonstrating good reliability and validity [15].

Fitbit

Fitbit employs an algorithm that measures sleep and wake times through motion sensors and heart rate measurements. This algorithm enables Fitbit to record sleep duration and the stages of sleep, including REM sleep, light sleep, and deep sleep. Additionally, the Fitbit device provides a sleep score by collecting individual sleep-related data during sleep, including sleep duration, sleep quality (time spent in deep sleep and REM sleep), and amount of restoration (heart rate and movement during sleep, etc.) [16]. The sleep score ranges from 0 to 100, with higher scores indicating better sleep quality. The Fitbit mobile application accessed the collected sleep data (Fig. 2). Individuals were asked to wear the device for three days before and after treatment, consistent with previous studies using Fitbit devices that have employed similar durations for sleep assessment [17–19]. In addition, prior research on wearable sleep trackers has indicated that three nights of monitoring can provide reliable estimates of habitual sleep [20]. In this study, the Fitbit Inspire 2 model was utilised. Lim et al. conducted a validation study of the Fitbit Inspire 2 model against polysomnography. They concluded that it can be used as an objective tool to measure sleep in daily life [21].

Fig. 2.

Fitbit mobile app screenshots

Intervention

Manual diaphragm release

Participants were lying on their backs, and the therapist placed their fingers under the costal arch. During expiration, the therapist applied deeper pressure with their fingers, increasing the pressure during inspiration while accompanying the movement of the ribs. This technique progressively deepens the pressure into the costal arch with each breath. The diaphragm release technique was administered in two sets of 10 deep breaths per session, with three sessions conducted and two rest days between each session [22].

Statistical analysis

The data were analysed using SPSS^® (Statistical Package for Social Sciences) version 22. Continuous variables were presented as mean ± standard deviation, while categorical variables were expressed as numbers and percentages. The normal distribution of variables was assessed using the Shapiro-Wilk test. Parametric test conditions were considered when analysing variables with the Paired Sample T-Test, whereas non-parametric test conditions were applied when using the Wilcoxon Signed Ranks Test. Cohen effect size (d) measurement was used to determine the magnitude of change in the evaluated para-meters. Cohen’s recommendations were used to interpret the effect sizes of the mean differences: d < 0.20 negligible; d = 0.20–0.50 small; d = 0.50–0.80 medium and d >0.8 large effect size [23]. A significance level of p < 0.05 was adopted for all statistical analyses.

Results

The characteristics of individuals are presented in Table 1. At baseline, 24 participants (68.6%) scored above the PSQI cut-off (> 5), indicating poor sleep quality.

Table 1.

The characteristics of the participants

Mean ± SD
Age (years)	23.57 ± 3.57
Height (cm)	166.97 ± 8.17
Weight (kg)	63.13 ± 11.78
BMI (kg/m 2 )	22.58 ± 3.28
n (%)
Gender
Male	10 (28.6)
Female	25 (71.4)
Smoking
Yes	8 (22.9)
No	27 (77.1)

Following the intervention, there were notable increases in sleep duration and sleep score as per Fitbit measurements (p < 0.05). However, no significant differences were observed in awake time, REM sleep, light sleep and deep sleep after the intervention (p > 0.05) (Table 2).

Table 2.

Sleep stages and sleep score (Fitbit) pre and post-intervention

	Pre-intervention	Post-intervention	p	Cohen’s d effect size
Sleep time (minutes)	371.22 ± 48.68	398.00 ± 51.98	0.026 b	0.531
Awake time (%)	12.80 ± 2.69	12.82 ± 2.83	0.962a	0.007
REM sleep (%)	21.40 ± 5.56	21.81 ± 5.48	0.704a	0.073
Light sleep (%)	59.75 ± 6.81	58.08 ± 7.87	0.252a	0.227
Deep sleep (%)	18.86 ± 3.20	20.11 ± 4.36	0.062b	0.327
Sleep score (0–100)	74.87 ± 5.71	77.87 ± 5.70	0.006 a	0.526

^aPaired Sample T-Test, ^bWilcoxon Signed Ranks Test

Post-intervention, there was a significant enhancement in sleep latency, sleep duration, sleep disturbance subscales, and total score of PSQI (p < 0.05). Conversely, there were no discernible differences in PSQI’s subjective sleep quality, sleep efficiency, use of sleep medication, and daytime dysfunction subscales following the intervention (p > 0.05) (Table 3).

Table 3.

PSQI scores pre and post-intervention

	Pre-intervention	Post-intervention	p	Cohen’s d effect size
PSQI - Subjective sleep quality	1.17 ± 0.62	1.06 ± 0.34	0.248b	0.220
PSQI - Sleep latency	1.57 ± 0.98	1.17 ± 0.75	0.001 b	0.458
PSQI - Sleep duration	1.17 ± 0.82	0.77 ± 0.65	0.015 b	0.541
PSQI - Sleep efficiency	0.14 ± 0.49	0.11 ± 0.47	0.888b	0.063
PSQI - Sleep disturbance	1.46 ± 0.61	1.17 ± 0.57	0.008 b	0.491
PSQI - Use of sleep medication	0.06 ± 0.34	0.09 ± 0.51	0.317b	0.069
PSQI - Daytime dysfunction	1.14 ± 0.88	0.97 ± 0.86	0.225b	0.195
PSQI - Total Score	6.71 ± 2.97	5.34 ± 1.94	0.001 a	0.546

^aPaired Sample T-Test, ^bWilcoxon Signed Ranks Test, PSQI: Pittsburgh Sleep Quality Index

Discussion

The current pilot study investigated the preliminary effects of diaphragm release on sleep quality in healthy individuals. The findings suggest potential improvements in both subjective (PSQI) and objective (Fitbit) sleep parameters following a short-term diaphragm release intervention. To our knowledge, this is the first study to explore this relationship, contributing novel insights into the potential role of diaphragm release in sleep regulation.

While there is a dearth of literature on the subject, Mosa et al. explored the effects of abdominal breathing, akin to diaphragm release and stretching, on sleep. Their findings indicated improved sleep among patients with gastroesophageal reflux, suggesting a potential remedy for diaphragm dysfunction caused by this condition [24]. Similarly, Liu et al. demonstrated that diaphragmatic breathing enhanced sleep quality in nurses [8]. This technique augments the diaphragm’s range of motion, facilitating better gas exchange and promoting parasympathetic activity, thereby reducing cortisol secretion and neurohumoral transmission [25, 26]. Consequently, diaphragmatic breathing aids relaxation, potentially alleviating fatigue and psychological stress by optimising brain energy consumption and cortisol secretion [8, 25]. Therefore, it is widely believed that diaphragmatic breathing enhances sleep quality. Similarly, diaphragm release can augment diaphragm activity by promoting more unrestrained movement, potentially eliciting physiological responses akin to diaphragmatic breathing. This enhancement in diaphragm function primarily contributes to improved sleep quality by regulating respiratory and autonomic systems.

The present study observed significant enhancements in sleep latency, duration, sleep disturbance subscales, and the total PSQI score post-intervention. However, there were no changes in PSQI’s subjective sleep quality, sleep efficiency, use of sleep medication, and daytime dysfunction subscales, albeit improvements were noted across PSQI subscales. Similarly, while sleep quality measured with Fitbit increased, there were no discernible differences in the percentage of sleep phases. This outcome might be attributed to the intervention’s limited application, which was administered over three sessions. Expanding the number of sessions may yield further enhancements. To aid interpretation of the clinical relevance of the findings, effect size calculations were conducted. Cohen’s d values ranged from small to moderate across the significant PSQI and Fitbit variables, with most showing moderate effect sizes. These findings support the preliminary utility of diaphragm release in improving sleep-related parameters.

At baseline, 24 participants (68.6%) scored above the PSQI cutoff (>5), indicating poor sleep quality. After the intervention, this number decreased to 17 participants (48.6%), reflecting a clinically meaningful reduction in the proportion of individuals with poor sleep quality. In addition, the observed increase in sleep duration brought participants closer to the recommended 7–9 h of nightly sleep for adults, as outlined by the National Sleep Foundation [27]. A reduction in sleep latency was also noted, moving values toward the normal threshold of less than 30 min [28]. Sleep efficiency did not significantly change; however, it showed a tendency toward improvement approaching the 85% cutoff commonly used to define good sleep quality [28]. Taken together, these normative comparisons suggest that the observed changes may be clinically as well as statistically meaningful.

Sleep disorders are prevalent and impose substantial burdens on individuals and society, necessitating interventions to improve health outcomes. Poor sleep quality can exacerbate various health conditions, including hypertension, depression, diabetes, obesity, cardiovascular diseases, cognitive impairments, dementia, and stroke. Diaphragmatic release into treatment regimens may mitigate sleep issues and enhance sleep quality. As a manual therapy technique, diaphragm release is cost-effective and less likely to yield side effects compared to pharmacological and interventional approaches.

While the present findings are encouraging, they must be interpreted cautiously. Given the lack of a control group, the short duration of the intervention, and the reliance on a commercial wearable device, the results are best viewed as preliminary. Nevertheless, this pilot study provides a foundation for future randomized controlled trials that incorporate validated clinical tools and broader participant demographics.

Limitations

This study has several limitations as well as notable strengths. Diaphragmatic tension was not assessed prior to the intervention; including such an evaluation could have strengthened the findings by identifying participants with pre-existing diaphragm dysfunction. The lack of a follow-up period limits our ability to evaluate the long-term effects and sustainability of the observed improvements. Future studies should include follow-up measurements to assess the durability of outcomes over time.

The absence of a control group restricts causal inferences, as improvements in sleep parameters may have been influenced by external or behavioral factors unrelated to the intervention. The sample predominantly consisted of young, healthy individuals with a relatively low baseline risk of sleep disturbances, which may limit the generalizability of the findings to more clinically relevant populations.

Although Fitbit offers an accessible and non-invasive method for tracking sleep patterns, its algorithm is proprietary and subject to updates over time. Moreover, Fitbit is not equivalent to clinical-grade tools such as polysomnography or home sleep testing, which limits the precision and reliability of the sleep-related outcomes.

Medication use, including agents that may influence sleep quality, was not formally controlled or recorded, which may have introduced potential confounding effects. While autonomic nervous system modulation was proposed as a possible mechanism underlying the effects of diaphragm release, we did not include any direct physiological assessments, such as heart rate variability analysis, to support this hypothesis.

No data on participant perceptions or acceptability of the diaphragm release technique were collected, which may be considered a limitation. Future studies could include feasibility and acceptability measures to better understand how individuals experience the intervention.

Taken together, these limitations highlight the need for cautious interpretation of the findings. However, the study’s novelty as the first to explore the potential impact of diaphragm release on sleep quality underscores its exploratory value and provides a foundation for future, more comprehensive studies.

Conclusions

This pilot feasibility study suggests that diaphragm release is a safe and well-tolerated technique that may offer preliminary benefits in improving sleep quality. However, due to the exploratory nature of the study and its methodological limitations, the findings should be interpreted with caution. Further research employing randomized controlled designs, control groups, and validated clinical instruments such as polysomnography is needed to confirm these initial observations.

Authors' contributions

Concept development: EE, Design: EE, MK, Supervision: EE, Data collection: EE, MK, Analysis: EE, Writing: EE, MK, Critical review: EE, MK.

Funding

This study was funded by the Scientific and Technological Research Council of Turkey within the scope of project 2209-A.

Data availability

The data of this study are available from the corresponding author upon reasonable request. The data are not publicly available due to privacy or ethical restrictions.

Declarations

Ethics approval and consent to participate

Informed consent was obtained from the participants. The study was approved by the Tokat Gaziosmanpaşa University Ethics Committee.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.