Post-COVID-19 SyndromeNCT07545499
Physical Functions and Lifestyle Behaviours in Post-COVID-19 Syndrome Based on Circadian Rhythms
An observational study of Post-COVID-19 Syndrome, run by Hacettepe University at 1 site in Turkey (Türkiye).
Trial summary
Post-COVID-19 syndrome is associated with persistent symptoms such as fatigue, reduced physical activity, and impaired respiratory function. Circadian rhythm differences (chronotype) may influence lifestyle behaviors including physical activity, nutrition, and sleep patterns. Read more about this study
- Who is it for?
- Ages 18 to 65 years
- Conditions the study is for
- Post-COVID-19 Syndrome
- How many people
- 50 participants
- Where
- 1 siteTurkey (Türkiye)
- Study dates
- 22 May 2025to 22 May 2027
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: The study population consists of post-COVID-19 syndrome patients aged 18-65 years who are referred to the Hacettepe University Cardiopulmonary Rehabilitation Unit. Participants will be classified into morning-type and evening-type chronotypes.
Who may be able to join
- Diagnosed with Post-COVID-19 Syndrome
- Aged between 18-65 years
- Able to read and understand Turkish
- Voluntary participation
- Classified as Post-Covid Functional Status Scale (PCFS) grade 2-3
- Clinically stable condition
- No uncontrolled comorbidities (e.g., hypertension, diabetes under control)
- No orthopedic or neurological conditions affecting exercise testing
Who cannot join
- Recent myocardial infarction or pulmonary embolism
- Severe uncontrolled chronic diseases
- Neurological or orthopedic conditions limiting mobility
- Psychiatric or neurological disorders affecting cooperation or test compliance
- Inability to complete assessments
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Turkey (Türkiye)1 site, 1 recruiting
- Recruiting
Hacettepe University Faculty of Physical Therapy and Rehabilitation
Ankara, Altindağ, 06100
EBRU ÇALIK, Professor, +905442850087, ecalik85@gmail.com
About this study
Official title: Comparison of Respiratory Muscle Strength, Physical Activity Level, and Dietary Habits in Individuals With Post-COVID-19 Syndrome Having Different Circadian Rhythms
Post-COVID-19 syndrome is associated with persistent symptoms such as fatigue, reduced physical activity, and impaired respiratory function. Circadian rhythm differences (chronotype) may influence lifestyle behaviors including physical activity, nutrition, and sleep patterns.
This observational cross-sectional study aims to compare respiratory muscle strength, physical activity levels, and nutritional habits among individuals with post-COVID-19 syndrome according to their chronotype (morning, intermediate, and evening types).
Additionally, genetic analysis of the CLOCK gene polymorphism will be performed to support objective evaluation of circadian rhythm differences. The findings of this study may help to better understand the role of circadian rhythm in post-COVID-19 syndrome and contribute to the development of individualized rehabilitation and lifestyle interventions.
Read the detailed description
Post-COVID-19 syndrome is characterized by persistent symptoms such as fatigue, reduced exercise tolerance, and impaired respiratory function following acute SARS-CoV-2 infection. Emerging evidence suggests that circadian rhythm disruption may play a role in the pathophysiology of these symptoms by affecting metabolic regulation, hormonal balance, sleep quality, and physical performance.
Circadian rhythm varies between individuals and is commonly classified into chronotypes as morning, intermediate, and evening types. These chronotypes are associated with differences in daily activity patterns, nutritional behaviors, and physiological performance.
The aim of this observational cross-sectional study is to compare respiratory muscle strength, physical activity levels, nutritional habits, sleep quality, fatigue perception, and gastrointestinal symptoms in individuals with post-COVID-19 syndrome according to their chronotype.
Participants aged 18-65 years with a confirmed diagnosis of post-COVID-19 syndrome will be included. Chronotype will be assessed using the Munich Chronotype Questionnaire (MCTQ). Respiratory muscle strength will be evaluated using maximal inspiratory and expiratory pressures (MIP/MEP), and dynamic respiratory parameters will be assessed using a POWERbreathe device. Respiratory muscle endurance will be measured using threshold loading protocols.
Physical activity levels will be assessed using the International Physical Activity Questionnaire (IPAQ), while nutritional intake will be evaluated using 24-hour dietary recall. Sleep quality, fatigue severity, and gastrointestinal symptoms will be assessed using validated questionnaires.
In addition, blood samples will be collected for genetic analysis of the CLOCK gene polymorphism (rs1801260) using PCR-RFLP techniques to provide an objective assessment of circadian rhythm differences.
This study is expected to provide comprehensive insight into the relationship between circadian rhythm and functional, behavioral, and physiological outcomes in post-COVID-19 syndrome, and may contribute to the development of individualized rehabilitation strategies.
- Conditions
- Post-COVID-19 Syndrome
- Keywords
- Circadian Rhythm, Chronotype, Respiratory Muscle Strength, Physical Activity, Nutrition, Post-COVID, Long COVID, CLOCK Gene, Genetic Polymorphism
- Medical subject headings
- Post-Acute COVID-19 Syndrome, Motor Activity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
| Study group | Role | What they receive |
|---|---|---|
| Morning Types (Larks) | People who wake up early, feel most energetic in the morning, and reach their peak performance early in the day. | |
| Evening Types (Owls) | People who stay up late, struggle with early mornings, and reach their peak functional capacity in the late afternoon or evening. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Respiratory Muscle Strength
Maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP) values will be recorded with mouth pressure device.
Measured: Time Frame: Day 1
Dynamic respiratory muscle strength
Respiratory muscle strength index (S index) will be assessed using a portable POWERbreathe K5 device.
Measured: Time Frame: Day 1
Respiratory muscle endurance
Respiratory muscle endurance test at constant threshold load will be used.
Measured: Time Frame: Day 1
Secondary outcomes (7)
Physical Activity Level
Physical activity levels will be assessed using the International Physical Activity Questionnaire Short Form (IPAQ-SF), expressed as MET-min/week.
The total weekly IPAQ score (MET-min/week) were then used to classify participants into three categories:
Low PA (individuals who did not meet criteria for moderate or high categories); Moderate PA (≥3 days of vigorous-intensity activity of at least 20 min per day; ≥5 days of moderate-intensity activity and/or walking of at least 30 min per day; or 3-5 or more days of any combination of walking, moderate-intensity or vigorous intensity activities achieving a minimum total PA of at least 600 MET-min/week); high PA (vigorous activity on at least 3 days with a minimum total PA of at least 1500 MET-min/week or 7 days of any combination of walking and moderate or vigorous activities with a minimum total PA of 3000 MET-min/week).
Measured: Time Frame: Day 1
Dietary Intake
Dietary intake will be assessed using 24-hour dietary recall records analyzed for macro and micronutrient intake.
Measured: Time Frame: Day 1
Chronotype Classification
Chronotype will be determined using the Munich Chronotype Questionnaire (MCTQ), categorizing participants into morning-type and evening-type groups.Total MCTQ scores can range from 16 to 86, with the lowest values representing extreme-late chronotypes.
Measured: Time Frame: Day 1
Fatigue Severity
Fatigue will be assessed using the Fatigue Severity Scale (FSS). Total FSS score ranges between 0-7. Total FSS score 4 and more indicates severe fatigue.
Measured: Time Frame: Day 1
Gastrointestinal Symptoms
Gastrointestinal symptoms will be evaluated using the Gastrointestinal Symptom Rating Scale (GSRS).The total GSRS score ranges from 15 to 105, with higher scores indicating more severe gastrointestinal symptoms.
Measured: Time Frame: Day 1
Sleep Quality
Sleep quality will be evaluated using the Pittsburgh Sleep Quality Index (PSQI). Total PSQI score ranges from 0 to 21, with higher scores indicating poorer sleep quality. A total score greater than 5 is widely used as the cutoff, suggesting poor sleep quality.
Measured: Time Frame: Day 1
Classificationof human faeces forms
Classification of human faeces forms will be evaluated using the Bristol Stool Scale.The seven types of stool are recorded by this scale.
Type 1: Separate hard lumps, like nuts (difficult to pass) Type 2: Sausage-shaped, but lumpy Type 3: Like a sausage but with cracks on its surface Type 4: Like a sausage or snake, smooth and soft (average stool) Type 5: Soft blobs with clear cut edges Type 6: Fluffy pieces with ragged edges, a mushy stool (diarrhea) Type 7: Watery, no solid pieces, entirely liquid (diarrhea)
Measured: Time Frame: Day 1
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted22 Apr 2026
- Study start22 May 2025
- Primary completion22 Aug 2026 (estimated)
- Study completion22 May 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for Post-COVID-19 SyndromeStudies of the same condition, open and under way.
- More trials run by Hacettepe UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Other
- Time perspective
- Cross-sectional
- Enrolment
- 50 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Hacettepe University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Ebru Calik, Hacettepe University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07545499
- Sponsor's protocol ID
- FTREK25/33
- Status last verified
- Apr 2026
- First submitted
- 14 Apr 2026
- Last updated
- 22 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Suwazono Y, Dochi M, Sakata K, Okubo Y, Oishi M, Tanaka K, Kobayashi E, Kido T, Nogawa K. A longitudinal study on the effect of shift work on weight gain in male Japanese workers. Obesity (Silver Spring). 2008 Aug;16(8):1887-93. doi: 10.1038/oby.2008.298. Epub 2008 Jun 5.
PubMed 18535539Voigt RM, Forsyth CB, Green SJ, Engen PA, Keshavarzian A. Circadian Rhythm and the Gut Microbiome. Int Rev Neurobiol. 2016;131:193-205. doi: 10.1016/bs.irn.2016.07.002. Epub 2016 Sep 6.
PubMed 27793218
Study at a glance
From the registry record, last updated by the sponsor on 22 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Comparison of Respiratory Muscle Strength, Physical Activity Level, and Dietary Habits in Individuals With Post-COVID-19 Syndrome Having Different Circadian Rhythms
- ClinicalTrials.gov ID
- NCT07545499
- Acronym / sponsor ID
- FTREK25/33
- Conditions
- Post-COVID-19 Syndrome
- Keywords
- Circadian Rhythm, Chronotype, Respiratory Muscle Strength, Physical Activity, Nutrition, Post-COVID, Long COVID, CLOCK Gene
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 50 participants (estimated)
- Lead sponsor
- Hacettepe UniversityUniversity, hospital or other
- Study start
- 22 May 2025 (actual)
- Primary completion
- 22 Aug 2026 (estimated)
- Study completion
- 22 May 2027 (estimated)
- First posted
- 22 Apr 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Post-COVID-19 syndrome is associated with persistent symptoms such as fatigue, reduced physical activity, and impaired respiratory function. Circadian rhythm differences (chronotype) may influence lifestyle behaviors including physical activity, nutrition, and sleep patterns.
This observational cross-sectional study aims to compare respiratory muscle strength, physical activity levels, and nutritional habits among individuals with post-COVID-19 syndrome according to their chronotype (morning, intermediate, and evening types).
Additionally, genetic analysis of the CLOCK gene polymorphism will be performed to support objective evaluation of circadian rhythm differences. The findings of this study may help to better understand the role of circadian rhythm in post-COVID-19 syndrome and contribute to the development of individualized rehabilitation and lifestyle interventions.
Detailed description
Post-COVID-19 syndrome is characterized by persistent symptoms such as fatigue, reduced exercise tolerance, and impaired respiratory function following acute SARS-CoV-2 infection. Emerging evidence suggests that circadian rhythm disruption may play a role in the pathophysiology of these symptoms by affecting metabolic regulation, hormonal balance, sleep quality, and physical performance.
Circadian rhythm varies between individuals and is commonly classified into chronotypes as morning, intermediate, and evening types. These chronotypes are associated with differences in daily activity patterns, nutritional behaviors, and physiological performance.
The aim of this observational cross-sectional study is to compare respiratory muscle strength, physical activity levels, nutritional habits, sleep quality, fatigue perception, and gastrointestinal symptoms in individuals with post-COVID-19 syndrome according to their chronotype.
Participants aged 18-65 years with a confirmed diagnosis of post-COVID-19 syndrome will be included. Chronotype will be assessed using the Munich Chronotype Questionnaire (MCTQ). Respiratory muscle strength will be evaluated using maximal inspiratory and expiratory pressures (MIP/MEP), and dynamic respiratory parameters will be assessed using a POWERbreathe device. Respiratory muscle endurance will be measured using threshold loading protocols.
Physical activity levels will be assessed using the International Physical Activity Questionnaire (IPAQ), while nutritional intake will be evaluated using 24-hour dietary recall. Sleep quality, fatigue severity, and gastrointestinal symptoms will be assessed using validated questionnaires.
In addition, blood samples will be collected for genetic analysis of the CLOCK gene polymorphism (rs1801260) using PCR-RFLP techniques to provide an objective assessment of circadian rhythm differences.
This study is expected to provide comprehensive insight into the relationship between circadian rhythm and functional, behavioral, and physiological outcomes in post-COVID-19 syndrome, and may contribute to the development of individualized rehabilitation strategies.
Study design
- Observational model
- Other
- Time perspective
- Cross-sectional
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Morning Types (Larks) | – | –People who wake up early, feel most energetic in the morning, and reach their peak performance early in the day. |
| Evening Types (Owls) | – | –People who stay up late, struggle with early mornings, and reach their peak functional capacity in the late afternoon or evening. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- The study population consists of post-COVID-19 syndrome patients aged 18-65 years who are referred to the Hacettepe University Cardiopulmonary Rehabilitation Unit. Participants will be classified into morning-type and evening-type chronotypes.
Key inclusion criteria (8 listed)
- Diagnosed with Post-COVID-19 Syndrome
- Aged between 18-65 years
- Able to read and understand Turkish
- Voluntary participation
- Classified as Post-Covid Functional Status Scale (PCFS) grade 2-3
Key exclusion criteria (5 listed)
- Recent myocardial infarction or pulmonary embolism
- Severe uncontrolled chronic diseases
- Neurological or orthopedic conditions limiting mobility
- Psychiatric or neurological disorders affecting cooperation or test compliance
- Inability to complete assessments
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Primary outcome
Respiratory Muscle Strength
Time frame: Time Frame: Day 1
Maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP) values will be recorded with mouth pressure device.
Dynamic respiratory muscle strength
Time frame: Time Frame: Day 1
Respiratory muscle strength index (S index) will be assessed using a portable POWERbreathe K5 device.
Respiratory muscle endurance
Time frame: Time Frame: Day 1
Respiratory muscle endurance test at constant threshold load will be used.
7 secondary outcomes
Physical Activity Level
Time frame: Time Frame: Day 1
Dietary Intake
Time frame: Time Frame: Day 1
Chronotype Classification
Time frame: Time Frame: Day 1
Fatigue Severity
Time frame: Time Frame: Day 1
Gastrointestinal Symptoms
Time frame: Time Frame: Day 1
Sleep Quality
Time frame: Time Frame: Day 1
Classificationof human faeces forms
Time frame: Time Frame: Day 1
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 22 Apr 2026.
- Background: PubMed 18535539Suwazono Y, Dochi M, Sakata K, Okubo Y, Oishi M, Tanaka K, Kobayashi E, Kido T, Nogawa K. A longitudinal study on the effect of shift work on weight gain in male Japanese workers. Obesity (Silver Spring). 2008 Aug;16(8):1887-93. doi: 10.1038/oby.2008.298. Epub 2008 Jun 5.
- Background: PubMed 27793218Voigt RM, Forsyth CB, Green SJ, Engen PA, Keshavarzian A. Circadian Rhythm and the Gut Microbiome. Int Rev Neurobiol. 2016;131:193-205. doi: 10.1016/bs.irn.2016.07.002. Epub 2016 Sep 6.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Post-COVID-19 Syndrome, run by Hacettepe University at 1 site in Turkey (Türkiye).
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 5 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 22 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Ebru Çalık, Professor (+905442850087, ecalik85@gmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Respiratory Muscle Strength (time frame: Time Frame: Day 1). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07545499, which also lists 2 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 22 Apr 2026.