The First-Night Effect and Sex Differences in Strength and Muscular Endurance Performance

NCT07758166 | Completed

• 1 other identifier: CEID/2023/6/119_1
• Study Type: interventional
• Target: 32
• Locations: 1 country
• Sites: 1

Brief 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. 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

Outcome Measures

Primary Outcomes (5)

• Mean velocity at different %1RM

  Mean velocity at different %1RM (25%, 50%, 75%, 90%)

  Through study completion, an average of 3 weeks

• Number of repetitions performed during 1 set at 65%1RM until task failure

  In bench press and back squat exercises

  Through study completion, an average of 3 weeks

• Bar velocity deplacement performed in 1 set at 65%1RM until task failure

  In bench press and back squat exercises

  Through study completion, an average of 3 weeks

• Handgrip and isometric mid-thigh pull tests

  N generated

  Through study completion, an average of 3 week

• Vertical Jump test (CMJ)

  cm of Height and W/kg generate during a CMJ

  Through study completion, an average of 3 week

Secondary Outcomes (1)

• Mood state (tension, depression, anger, vigor, fatigue and confusion)

  Through study completion, an average of 3 weeks

Study Arms (2)

8h Sleep at home

PLACEBO COMPARATOR

Participants sleep 8h at home

Behavioral: first-night effect (at home)

8h Sleep at the Laboratory

EXPERIMENTAL

Participants sleep 8h at the laboratory

Behavioral: First-Night Effect at the laboratory

Interventions

First-Night Effect at the laboratory BEHAVIORAL

Participants sleep 8h at the laboratory

8h Sleep at the Laboratory

first-night effect (at home) BEHAVIORAL

Participants sleep 8h at home

8h Sleep at home

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• University of Alcala: lead

Study Sites (1)

Facultad de Medicina y Ciencias de la Salud. Universidad de Alcalá

Alcalá de Henares, Madrid, 28805, Spain

Location

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: INVESTIGATOR
• Masking Details: Investigador and Statistician were blinded
• Purpose: OTHER
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Study Record Dates

• First Submitted: August 5, 2026
• First Posted: August 11, 2026
• Study Start: February 7, 2024
• Primary Completion: December 20, 2025
• Study Completion: May 3, 2026
• Last Updated: August 11, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will share

Locations

ES (1)