SleepNCT07758166
The First-Night Effect and Sex Differences in Strength and Muscular Endurance Performance
A study testing First-Night Effect at the laboratory and first-night effect (at home) in people with Sleep, run by University of Alcala at 1 site in Spain.
Trial summary
Introduction: The first-night effect, characterized by disturbed sleep in an unfamiliar environment, may impair next-day physical performance. However, whether this response differs between men and women remains unclear. Read more about this study
- Who is it for?
- Ages 18 to 40 yearsHealthy volunteers can take part
- Conditions the study is for
- Sleep
- What is being tested?
- First-Night Effect at the laboratory and first-night effect (at home)
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 32 participants
- Where
- 1 siteSpain
- Study dates
- 7 Feb 2024to 3 May 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
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 40 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Age between 18 and 35 years.• Body Mass Index (BMI) < 25 kg/m².
- Resistance-trained individuals (more than 2 years of structured training).
- Healthy men and women without neurological, cardiometabolic, immunological, or physical conditions that prevent them from exercising.
- Participants must be able to perform the tests described in the following section.
Who cannot join
- History of neuromuscular diseases, heart disease, or conditions that may affect liver or muscle metabolism.
- Use of drugs, stimulants, or sports supplements that could interfere with the dietary supplement used in the study.
- Sedentary habits (less than 150 minutes/week of moderate exercise).• Having undergone prolonged periods of physical inactivity in the 6 months prior to the study.
- Engaging in strenuous exercise within 48 hours prior to the tests.• Failure to replicate the same food intake on both experimental days.
- Consumption of caffeine or any other stimulant the day before the tests.
Trial locations and contacts
1 site in 1 country.
Spain1 site
Facultad de Medicina y Ciencias de la Salud. Universidad de Alcalá
Alcalá de Henares, Madrid, 28805
About this study
Official title: The First-Night Effect: Sex Differences in the Impact of Unfamiliar Sleeping Environment on Strength and Muscular Endurance Performance in Resistance-trained Participants
Introduction: The first-night effect, characterized by disturbed sleep in an unfamiliar environment, may impair next-day physical performance. However, whether this response differs between men and women remains unclear. This study investigated sex differences in the effects of sleeping in an unfamiliar environment on strength and muscular endurance in resistance-trained individuals.
Methods: Thirty-two resistance-trained participants (16 women, 16 men; 23 ± 4 years) completed a randomized, counterbalanced crossover study involving two conditions: sleeping for 8 h at home or in the laboratory. The following morning, participants performed bench press and back squat strength tests across 25-90%1RM, followed by muscular endurance tests to failure at 65%1RM.
- Conditions
- Sleep
- Being tested
- First-Night Effect at the laboratory, first-night effect (at home)
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
First-Night Effect at the laboratoryBehavioural
Participants sleep 8h at the laboratory
first-night effect (at home)Behavioural
Participants sleep 8h at home
| Study group | Role | What they receive |
|---|---|---|
| 8h Sleep at home | Placebo comparator | Participants sleep 8h at home Receives: Behavioral: first-night effect (at home) |
| 8h Sleep at the Laboratory | Experimental | Participants sleep 8h at the laboratory Receives: Behavioral: First-Night Effect at the laboratory |
What is being measured
The primary outcome is the main question the study is designed to answer.
Mean concentric velocity at 25%, 50%, 75%, and 90% 1RM (m/s)
Mean velocity at different %1RM (25%, 50%, 75%, 90%)
Measured: Through study completion, an average of 3 weeks
Number of repetitions performed to task failure during the bench press and back squat exercises at 65% 1RM.
In bench press and back squat exercises
Measured: Through study completion, an average of 3 weeks
Bar velocity displacement (mean velocity, m/s) performed in 1 set at 65%1RM until task failure
In bench press and back squat exercises
Measured: Through study completion, an average of 3 weeks
Maximal force during handgrip and isometric mid-thigh pull tests (N)
N generated
Measured: Through study completion, an average of 3 week
Vertical Jump test (CMJ)
cm of Height and W/kg generate during a CMJ
Measured: Through study completion, an average of 3 week
Secondary outcomes (1)
Mood state (tension, depression, anger, vigor, fatigue and confusion)
Participants graded a set of 29 items related to the mood on a Likert scale from 0 (not at all) to 4 (extremely) in reply to the question;How do you feel at this moment?; to assess six scales: tension, depression, anger, vigor, fatigue and confusion.
Measured: Through study completion, an average of 3 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted11 Aug 2026
- Study start7 Feb 2024
- Primary completion20 Dec 2025
- Study completion3 May 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for SleepStudies of the same condition, open and under way.
- 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
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind
- Who is masked
- Investigator
- Enrolment
- 32 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Alcala
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Alberto Pérez-López, University of Alcala
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07758166
- Sponsor's protocol ID
- CEID/2023/6/119_1
- Status last verified
- Aug 2026
- First submitted
- 5 Aug 2026
- Last updated
- 31 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes
Study at a glance
From the registry record, last updated by the sponsor on 31 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The First-Night Effect: Sex Differences in the Impact of Unfamiliar Sleeping Environment on Strength and Muscular Endurance Performance in Resistance-trained Participants
- ClinicalTrials.gov ID
- NCT07758166
- Acronym / sponsor ID
- CEID/2023/6/119_1
- Conditions
- Sleep
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 32 participants (actual)
- Lead sponsor
- University of AlcalaUniversity, hospital or other
- Study start
- 7 Feb 2024 (actual)
- Primary completion
- 20 Dec 2025 (actual)
- Study completion
- 3 May 2026 (actual)
- First posted
- 11 Aug 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.
Introduction: The first-night effect, characterized by disturbed sleep in an unfamiliar environment, may impair next-day physical performance. However, whether this response differs between men and women remains unclear. This study investigated sex differences in the effects of sleeping in an unfamiliar environment on strength and muscular endurance in resistance-trained individuals.
Methods: Thirty-two resistance-trained participants (16 women, 16 men; 23 ± 4 years) completed a randomized, counterbalanced crossover study involving two conditions: sleeping for 8 h at home or in the laboratory. The following morning, participants performed bench press and back squat strength tests across 25-90%1RM, followed by muscular endurance tests to failure at 65%1RM.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind (investigator)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| 8h Sleep at home | Placebo comparator | Behavioral: first-night effect (at home)Participants sleep 8h at home |
| 8h Sleep at the Laboratory | Experimental | Behavioral: First-Night Effect at the laboratoryParticipants sleep 8h at the laboratory |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Age between 18 and 35 years.• Body Mass Index (BMI) < 25 kg/m².
- Resistance-trained individuals (more than 2 years of structured training).
- Healthy men and women without neurological, cardiometabolic, immunological, or physical conditions that prevent them from exercising.
- Participants must be able to perform the tests described in the following section.
Key exclusion criteria (5 listed)
- History of neuromuscular diseases, heart disease, or conditions that may affect liver or muscle metabolism.
- Use of drugs, stimulants, or sports supplements that could interfere with the dietary supplement used in the study.
- Sedentary habits (less than 150 minutes/week of moderate exercise).• Having undergone prolonged periods of physical inactivity in the 6 months prior to the study.
- Engaging in strenuous exercise within 48 hours prior to the tests.• Failure to replicate the same food intake on both experimental days.
- Consumption of caffeine or any other stimulant the day before the tests.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| First-Night Effect at the laboratoryParticipants sleep 8h at the laboratory | Behavioural | 8h Sleep at the Laboratory |
| first-night effect (at home)Participants sleep 8h at home | Behavioural | 8h Sleep at home |
Primary outcome
Mean concentric velocity at 25%, 50%, 75%, and 90% 1RM (m/s)
Time frame: Through study completion, an average of 3 weeks
Mean velocity at different %1RM (25%, 50%, 75%, 90%)
Number of repetitions performed to task failure during the bench press and back squat exercises at 65% 1RM.
Time frame: Through study completion, an average of 3 weeks
In bench press and back squat exercises
Bar velocity displacement (mean velocity, m/s) performed in 1 set at 65%1RM until task failure
Time frame: Through study completion, an average of 3 weeks
In bench press and back squat exercises
Maximal force during handgrip and isometric mid-thigh pull tests (N)
Time frame: Through study completion, an average of 3 week
N generated
Vertical Jump test (CMJ)
Time frame: Through study completion, an average of 3 week
cm of Height and W/kg generate during a CMJ
1 secondary outcome
Mood state (tension, depression, anger, vigor, fatigue and confusion)
Time frame: Through study completion, an average of 3 weeks
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 31 Aug 2026.
- Individual participant dataSharing planned: Yes
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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. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing First-Night Effect at the laboratory and first-night effect (at home) in people with Sleep, run by University of Alcala at 1 site in Spain.
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 4 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: finished, as of the sponsor's last update on 31 Aug 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 Spain. 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. Some participants in this study may receive a placebo. 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?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Mean concentric velocity at 25%, 50%, 75%, and 90% 1RM (m/s) (time frame: Through study completion, an average of 3 weeks). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 31 Aug 2026.