Effects of Afternoon Napping, Caffeine and Recovery on Evening Athletic Performance (NAP-CAF-REC)

Effects of Afternoon Napping, Caffeine and Personalised Recovery Protocol on Evening Athletic Performance According to Sex and Chronotype: A Randomised Crossover Trial

This study investigates the effects of napping, caffeine, and a personalised recovery protocol on evening athletic performance in male and female athletes.

Background: Evening athletic performance can be impaired by accumulated sleepiness and natural circadian rhythms. Athletes often seek strategies to maintain peak performance during evening competitions. Napping, caffeine, and recovery protocols are commonly used but their combined effects, particularly differences between sexes and chronotypes (morning-type vs evening-type individuals), remain unclear.

Objective: To determine whether combining a 90-minute afternoon nap with moderate caffeine ingestion (5 mg/kg) and a brief personalised recovery protocol (dynamic stretching plus carbohydrate-protein snack) produces superior evening performance compared to each intervention alone.

Methods: Sixty elite university athletes (30 males, 30 females) will participate in a randomised, double-blind, placebo-controlled crossover trial. Each participant will complete five experimental conditions separated by at least 72 hours: (1) placebo, (2) nap alone, (3) caffeine alone, (4) nap plus caffeine, and (5) nap plus caffeine plus recovery protocol. Performance will be assessed at 19:00 using tests of agility, jumping, sprinting, and reaction time. Physiological measurements including heart rate variability, salivary cortisol, plasma brain-derived neurotrophic factor (BDNF), and blood lactate will be collected at multiple timepoints.

Expected Outcomes: The combined intervention (nap plus caffeine plus recovery) is expected to produce the greatest improvements in physical and cognitive performance, with potential differences between males and females and between morning-type and evening-type athletes.

Significance: Findings will provide evidence-based recommendations for athletes and coaches seeking to optimise evening performance through multi-modal strategies.

Study Overview

• Status: Completed
• Conditions: Circadian Rhythm; Athletic Performance; Exercise Performance; Sports Performance
• Intervention / Treatment: Other: Placebo; Behavioral: Afternoon Nap; Dietary supplement: Caffeine; Combination product: Personalised Recovery Protocol

Detailed Description

This is a mechanistic, randomised, double-blind, placebo-controlled crossover trial designed to examine the isolated and combined effects of afternoon napping, caffeine ingestion, and a personalised active recovery protocol on evening cognitive and physical performance in male and female athletes stratified by chronotype.

STUDY DESIGN:

The study employs a Latin square counterbalanced crossover design with five experimental conditions:

1. PLA: Placebo capsule at 18:00, no nap opportunity
2. NAP: 90-min nap opportunity (13:00-14:30) + placebo capsule at 18:00
3. CAF: Caffeine ingestion (5 mg/kg anhydrous caffeine) at 18:00, no nap opportunity
4. NAP+CAF: 90-min nap + caffeine (5 mg/kg) at 18:00
5. NAP+CAF+REC: 90-min nap + caffeine (5 mg/kg) at 18:00 + 15-min personalised active recovery protocol (dynamic stretching + carbohydrate-protein snack) from 18:45-19:00

Each condition is separated by a washout period of at least 72 hours to eliminate carryover effects.

PARTICIPANTS:

Sixty elite university athletes (30 males, 30 females; age 20.6 ± 1.5 years) will be recruited from the Higher Institute of Sport and Physical Education of Sfax, Tunisia. Participants will be classified as definite morning-type (MEQ score 59-86) or definite evening-type (MEQ score 16-41) using the Morningness-Eveningness Questionnaire. Female participants will be tested during the early follicular phase of the menstrual cycle (days 2-5) to control for hormonal variability.

Inclusion criteria: Regular training (≥10 hours/week), non-habitual nappers, caffeine-naïve (<80 mg/day), non-smokers, free from injury/medication, normal sleep quality (PSQI <5).

EXPERIMENTAL PROCEDURES:

Participants will arrive at the laboratory at 19:00 on the evening before each trial for standardisation (standardised dinner, sleep in laboratory-controlled conditions, standardised breakfast). On the experimental day, participants will remain sedentary until 12:00, consume a standardised lunch, then undergo the nap protocol or rest period (13:00-14:30). During nap conditions, objective sleep architecture will be recorded using a portable EEG headband (Dreem 3). Afternoon rest period (14:30-18:00) will be followed by capsule ingestion (18:00), recovery protocol (18:45-19:00, NAP+CAF+REC condition only), standardised warm-up (19:00-19:15), and testing battery (19:15-20:00).

OUTCOME MEASURES:

Primary outcome: Repeated Modified Agility Test (RMAT) total time

Secondary outcomes:

• Physical performance: Countermovement jump (CMJ), squat jump (SJ), 20-m sprint, RMAT fastest/slowest times, fatigue index
• Cognitive performance: Simple reaction time (SRT), choice reaction time (CRT)
• Subjective measures: Epworth Sleepiness Scale (ESS), Karolinska Sleepiness Scale (KSS)
• Physiological biomarkers: Heart rate variability (HRV-RMSSD, HF power), salivary cortisol (4 timepoints), plasma BDNF (2 timepoints), blood lactate (3 timepoints)
• Nap architecture (EEG): Total sleep time, sleep onset latency, time in N2/N3/REM, sleep efficiency

STATISTICAL ANALYSIS:

Linear mixed-effects models will be used with fixed effects for sex, chronotype, condition, timepoint (where applicable), and their interactions, with random intercepts for subject. Post-hoc comparisons will use Bonferroni correction. Significance level: p ≤ 0.01. Effect sizes: partial eta-squared (ηp²) and Cohen's d.

Sample size calculation (G*Power): Based on repeated agility performance (ηp² = 0.14, f = 0.40, α = 0.01, power = 0.95), minimum n = 56. With 10% dropout allowance, n = 60 will be recruited.

ETHICAL CONSIDERATIONS:

The study has received ethical approval from the institutional scientific committee of ISSEPS (Reference: ISSEPS/11-02-2026). All participants will provide written informed consent. The study is conducted in accordance with the Declaration of Helsinki (2013 revision).

REGISTRATION:

The protocol is registered on the Pan African Clinical Trials Registry (PACTR) and ClinicalTrials.gov.

DATA SHARING:

Anonymised participant data and statistical analysis code will be made publicly available on the Open Science Framework (OSF) upon publication.

• Study Type: Interventional
• Enrollment (Actual): 60
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Tunisia
  • Sfax, Tunisia, 3000
    • Higher Institute of Sport and Physical Education of Sfax (ISSEP Sfax)

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Regular engagement in at least 10 two-hour training sessions per week across various sports (team sports, judo, track and field, tennis, swimming)
• Non-habitual napping (fewer than one nap per week)
• Caffeine-naïve (habitual daily caffeine intake < 80 mg, verified by a 7-day dietary recall)
• Non-smokers and free from any regular medication or recreational drugs
• Free from any musculoskeletal injury in the previous month
• Normal sleep quality (Pittsburgh Sleep Quality Index score < 5)
• Classified as either definite morning-type (MEQ score 59-86) or definite evening-type (MEQ score 16-41) on the Morningness-Eveningness Questionnaire
• For female participants: eumenorrheic (regular menstrual cycle length 26-32 days), not using hormonal contraceptives, and no history of menstrual disorders

Exclusion Criteria:

• Intermediate chronotype (MEQ score 42-58)
• Habitual nappers (≥1 nap per week)
• High habitual caffeine intake (≥80 mg/day)
• Current use of any medication or recreational drugs
• Smokers
• Musculoskeletal injury within the previous month
• Poor sleep quality (PSQI score ≥ 5)
• Irregular menstrual cycle or use of hormonal contraceptives (for female participants)
• History of sleep disorders (e.g., insomnia, sleep apnea)
• Inability to complete all five experimental conditions

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

5

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: PLA; Placebo capsule (microcrystalline cellulose) at 18:00, no nap opportunity	Other: Placebo; Microcrystalline cellulose powder administered in opaque capsules at 18:00. Capsules were visually identical in appearance, mass, color, and odor to caffeine capsules.
Experimental: NAP; 90-minute afternoon nap opportunity (13:00-14:30) with objective sleep architecture recording via portable EEG headband (Dreem 3), followed by placebo capsule (microcrystalline cellulose) at 18:00. Participants remained in a quiet, dimly lit room during the nap opportunity.	Other: Placebo; Microcrystalline cellulose powder administered in opaque capsules at 18:00. Capsules were visually identical in appearance, mass, color, and odor to caffeine capsules.; Behavioral: Afternoon Nap; 90-minute afternoon nap opportunity (13:00-14:30) in a quiet, dimly lit room with objective sleep architecture monitoring using portable EEG headband (Dreem 3). Participants wore earplugs and eye masks. Sleep stages (N1, N2, N3, REM) were recorded.
Experimental: CAF; Caffeine ingestion (5 mg/kg body mass of anhydrous caffeine) at 18:00, no nap opportunity. Participants remained in a quiet, dimly lit room during the 13:00-14:30 period.	Dietary supplement: Caffeine; Anhydrous caffeine powder (5 mg per kg of body mass) administered in opaque capsules at 18:00. Capsules were visually identical to placebo capsules (microcrystalline cellulose). This dose is within the range of common dietary caffeine intake and is classified as a nutritional supplement.
Experimental: NAP+CAF; 90-minute afternoon nap opportunity (13:00-14:30) with EEG recording, followed by caffeine ingestion (5 mg/kg) at 18:00.	Behavioral: Afternoon Nap; 90-minute afternoon nap opportunity (13:00-14:30) in a quiet, dimly lit room with objective sleep architecture monitoring using portable EEG headband (Dreem 3). Participants wore earplugs and eye masks. Sleep stages (N1, N2, N3, REM) were recorded.; Dietary supplement: Caffeine; Anhydrous caffeine powder (5 mg per kg of body mass) administered in opaque capsules at 18:00. Capsules were visually identical to placebo capsules (microcrystalline cellulose). This dose is within the range of common dietary caffeine intake and is classified as a nutritional supplement.
Experimental: NAP+CAF+REC; 90-minute afternoon nap opportunity (13:00-14:30) with EEG recording, caffeine ingestion (5 mg/kg) at 18:00, plus 15-minute personalised active recovery protocol (18:45-19:00) consisting of dynamic stretching and a carbohydrate-protein snack (20g maltodextrin + 10g whey isolate).	Behavioral: Afternoon Nap; 90-minute afternoon nap opportunity (13:00-14:30) in a quiet, dimly lit room with objective sleep architecture monitoring using portable EEG headband (Dreem 3). Participants wore earplugs and eye masks. Sleep stages (N1, N2, N3, REM) were recorded.; Dietary supplement: Caffeine; Anhydrous caffeine powder (5 mg per kg of body mass) administered in opaque capsules at 18:00. Capsules were visually identical to placebo capsules (microcrystalline cellulose). This dose is within the range of common dietary caffeine intake and is classified as a nutritional supplement.; Combination product: Personalised Recovery Protocol; 15-minute active recovery protocol (18:45-19:00) consisting of: (1) dynamic stretching exercises targeting lower limb musculature (leg swings, walking lunges, high knees, butt kicks; 10 repetitions per leg), followed by (2) consumption of a carbohydrate-protein snack (30g total: 20g maltodextrin + 10g whey isolate, 2:1 ratio) mixed with 200mL water.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Repeated Modified Agility Test (RMAT) Total Time	Total time (seconds) to complete 10 maximal 20-m sprints with four changes of direction (forward sprint, left shuffle, right shuffle, backward sprint). The test was conducted on an indoor hardwood court using dual-beam photocells (Brower Timing Systems, Salt Lake City, UT, USA) placed at the start/finish line. Participants started from a standing position 0.5 m behind the first photocell. Lower values indicate better repeated agility performance. This was the primary outcome measure used for sample size calculation.	Measured at 19:45 (immediately after the testing battery) on each of the 5 experimental days

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Countermovement Jump (CMJ) Height	Maximum jump height (cm) calculated from flight time using the formula h = g·t²/8, where g = 9.81 m·s-². Participants started from an upright standing position, performed a rapid downward movement to approximately 90° knee flexion, and immediately jumped vertically, maintaining hands on hips throughout. Three maximal attempts were performed with 2 minutes of rest between attempts; the highest jump height was retained. Measured using an optical measurement system (Optojump Next, Microgate SRL, Bolzano, Italy) with a sampling frequency of 1000 Hz. Higher values indicate better explosive lower-limb performance.	Measured at approximately 19:30 during the post-testing battery on each of the 5 experimental days
Squat Jump (SJ) Height	Maximum jump height (cm) from a static squat position with knees at approximately 90° flexion, hands on hips. Participants held the starting position for 2-3 seconds before jumping vertically without any countermovement. Three maximal attempts were performed with 2 minutes of rest between attempts; the highest jump height was retained for analysis. Calculated from flight time using h = g·t²/8. Measured using Optojump Next optical system (1000 Hz sampling frequency). Higher values indicate better explosive lower-limb performance without stretch-shortening cycle contribution.	Measured at approximately 19:35 during the post-testing battery on each of the 5 experimental days
20-m Sprint Time	Best time (seconds) of two maximal 20-m sprints from a standing start, with 3 minutes of passive recovery between sprints. Participants started 0.5 m behind the start line. Sprint time was measured using dual-beam photocells (Brower Timing Systems, Salt Lake City, UT, USA) placed at the start (0 m) and finish (20 m) lines. Lower values indicate better linear sprint performance.	Measured at approximately 19:40 during the post-testing battery on each of the 5 experimental days
Simple Reaction Time (SRT)	Mean reaction time (milliseconds) across 15 recorded trials. A green circle appeared on a black background on a 15-inch laptop screen (60 Hz refresh rate), and participants pressed the space bar as quickly as possible. Inter-trial interval varied randomly between 1000 and 2000 ms. Measured using OpenSesame software (version 3.3). Lower values indicate faster simple reaction time and better cognitive processing speed.	Measured at approximately 19:15 (first test in the battery) on each of the 5 experimental days
Choice Reaction Time (CRT)	Mean reaction time (milliseconds) across 15 recorded trials. Either a red circle (press the left arrow key) or a blue square (press the right arrow key) appeared randomly on a 15-inch laptop screen (60 Hz refresh rate). Participants had to identify the stimulus and press the correct key as quickly as possible. Inter-trial interval varied randomly between 1000 and 2000 ms. Measured using OpenSesame software (version 3.3). Lower values indicate faster choice reaction time and better cognitive decision-making speed.	Measured at approximately 19:20 (second test in the battery) on each of the 5 experimental days
Heart Rate Variability (HRV-RMSSD)	Time-domain and frequency-domain parameters of heart rate variability recorded during 5 minutes in a supine resting position with spontaneous breathing. RR intervals were measured using a Polar H10 chest strap (Polar Electro, Kempele, Finland) with 1000 Hz sampling frequency. Primary parameter: RMSSD (root mean square of successive differences between normal heartbeats, in ms). Secondary parameter: HF power (high-frequency power, 0.15-0.40 Hz, in normalized units). Data were analyzed using Kubios HRV software (version 3.5) with artefact correction. Higher RMSSD values indicate greater parasympathetic (vagal) activity and better autonomic recovery.	Measured at three timepoints on each experimental day: baseline (12:00), pre-intervention (18:00), and post-testing (19:45)
Salivary Cortisol Concentration	Salivary cortisol concentration (nmol/L) measured using Salivette cotton swabs (Sarstedt, Nümbrecht, Germany). Participants were instructed to avoid eating, drinking (except water), and brushing teeth for 30 minutes before each sample. Samples were centrifuged at 1500×g for 10 minutes at 4°C, and the supernatant was stored at -80°C until analysis. Cortisol concentration was measured in duplicate using a high-sensitivity enzyme-linked immunosorbent assay (ELISA, IBL International, Hamburg, Germany) with a detection limit of 0.05 ng/mL and intra- and inter-assay coefficients of variation < 8%. Lower values indicate reduced hypothalamic-pituitary-adrenal (HPA) axis activity.	Measured at four timepoints on each experimental day: baseline (12:00), pre-intervention (18:00), post-testing (19:45), and 30 minutes post-exercise (20:30)
Plasma Brain-Derived Neurotrophic Factor (BDNF)	BDNF concentration (pg/mL) measured in venous blood samples (5 mL) drawn from an antecubital vein. Blood was collected into EDTA tubes, immediately centrifuged at 1500×g for 15 minutes at 4°C, and plasma was stored at -80°C until analysis. BDNF concentration was quantified using a commercially available ELISA kit (R&D Systems, Minneapolis, MN, USA; catalogue number DBD00) with a detection limit of 20 pg/mL and intra- and inter-assay CVs < 6% and < 9%, respectively. Higher values indicate greater neurotrophic activity.	Measured at two timepoints on each experimental day: baseline (12:00) and post-testing (19:45)
Blood Lactate Concentration	Lactate concentration (mmol/L) measured in capillary blood samples (5 µL) collected from the fingertip using a Lactate Pro 2 analyzer (Arkray, Kyoto, Japan), which has a coefficient of variation < 3%. Higher values indicate greater metabolic perturbation and glycolytic activation during high-intensity exercise.	Measured at three timepoints on each experimental day: pre-warm-up (18:55), 3 minutes post-RMAT, and 3 minutes post-20m sprint
Nap Architecture (EEG)	Objective sleep parameters recorded using a validated dry-electrode portable EEG headband (Dreem 3, Paris, France) with six channels (F3, F4, C3, C4, O1, O2, referenced to linked mastoids). Sleep stages were automatically scored in 30-second epochs using the manufacturer's algorithm and visually corrected by a certified sleep technologist blinded to condition and participant. Parameters extracted: total sleep time (TST, minutes), sleep onset latency (SOL, minutes), time in N2 sleep (minutes), time in N3 slow-wave sleep (minutes), time in REM sleep (minutes), and sleep efficiency (TST/time in bed × 100, %).	Recorded during the 90-minute nap opportunity (13:00-14:30) on NAP, NAP+CAF, and NAP+CAF+REC conditions only

Collaborators and Investigators

• Sponsor: The Higher Institute of Sport and Physical Education of Sfax
• Investigators: Principal Investigator: Kais El Abed, Phd, University of Sfax, Tunisia

Publications and helpful links

Helpful Links

• Open Science Framework - Data Repository

Study record dates

Study Major Dates

• Study Start (Actual): January 2, 2025
• Primary Completion (Actual): May 31, 2025
• Study Completion (Actual): May 31, 2025

Study Registration Dates

• First Submitted: June 10, 2026
• First Submitted That Met QC Criteria: June 11, 2026
• First Posted (Actual): June 17, 2026

Study Record Updates

• Last Update Posted (Actual): June 17, 2026
• Last Update Submitted That Met QC Criteria: June 11, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Heart Rate Variability; Caffeine; Reaction Time; Brain-Derived Neurotrophic Factor; Agility; Sex Differences; Randomised Controlled Trial; Chronotype; Napping; Crossover Trial; Jump Performance; Recovery Protocol; Evening Performance
• Additional Relevant MeSH Terms: Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Alkaloids; Purinones; Purines; Xanthines; Caffeine
• Other Study ID Numbers: ISSEPS-NAP-CAF-REC-2025; ISSEPS/11-02-2026 (Other Identifier: Higher Institute of Sport and Physical Education of Sfax (ISSEPS), Tunisia)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Anonymised individual participant data (IPD) will be shared for all 60 participants across all five experimental conditions (300 experimental sessions). Data will include: demographic characteristics, anthropometric measures, chronotype classification (MEQ scores), sleep quality (PSQI scores), nap architecture (EEG-derived sleep stages), physical performance outcomes (RMAT, CMJ, SJ, 20-m sprint), cognitive performance outcomes (SRT, CRT), subjective sleepiness (ESS, KSS), and physiological biomarkers (HRV-RMSSD, HF power, salivary cortisol, plasma BDNF, blood lactate). All data will be fully anonymised using coded identifiers (S01-S60), with the identification key stored separately on encrypted institutional servers.
• IPD Sharing Time Frame: IPD and supporting information are currently available on the Open Science Framework (OSF) repository at https://osf.io/3wq5j/. The dataset includes anonymised individual participant data (n=60, 300 experimental sessions), the R statistical analysis script, and the ethical approval certificate. Data will remain accessible indefinitely. Upon publication of the study results in a peer-reviewed journal, additional supporting documents (study protocol, statistical analysis plan, and informed consent form) will be added to the repository.
• IPD Sharing Access Criteria: The anonymised IPD and supporting documents will be openly accessible to any researcher, clinician, or member of the public without restriction. No formal request process or approval is required. Users may download the data directly from the Open Science Framework (OSF) repository once deposited. Researchers who reuse the data are requested to cite the original publication and the OSF dataset DOI. The data are provided "as is" without any warranty or guarantee of accuracy.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No