UMIN-CTR Clinical Trial

Public title

Acute effects of repeated caffeine nasal spray administration on cycling responses during simulated 10-km cycling, Stroop performance, and plasma caffeine concentrations

Acronym

caffeine nasal spray study

Scientific Title

Acute effects of repeated caffeine nasal spray administration on cycling responses during simulated 10-km cycling, Stroop performance, and plasma caffeine concentrations

Scientific Title:Acronym

caffeine nasal spray study

Region

Asia(except Japan)

Condition

Healthy adult men, including physically active participants and moderately trained cyclists

Classification by specialty

Adult

Classification by malignancy

Others

Genomic information

NO

Narrative objectives1

To examine the acute effects of repeated caffeine nasal spray administration at 15 and 20 mg/mL, compared with placebo, on self-selected cadence and device-derived completion time during constant-power simulated 10-km cycling, Stroop performance, and plasma caffeine concentrations in healthy physically active men and trained cyclists.

Basic objectives2

Efficacy

Basic objectives -Others

Trial characteristics_1

Exploratory

Trial characteristics_2

Explanatory

Developmental phase

Not applicable

Primary outcomes

Mean self-selected cadence, expressed in revolutions per minute, recorded throughout the constant-power simulated 10-km cycling protocol under the placebo, 15 mg/mL, and 20 mg/mL caffeine nasal spray conditions.

Key secondary outcomes

Device-derived completion time for the constant-power simulated 10-km cycling protocol.
Reaction time and accuracy in the neutral and incongruent Stroop conditions, assessed before and immediately after cycling.
Plasma caffeine concentration, measured before and immediately after cycling.
Heart rate and rating of perceived exertion measured during cycling.
Nasal, oral, gastrointestinal, neurological, muscular, and sleep-related side effects assessed at baseline, immediately after exercise, and 24 h after each trial.

Study type

Interventional

Basic design

Cross-over

Randomization

Randomized

Randomization unit

Individual

Blinding

Double blind -all involved are blinded

Control

Placebo

Stratification

NO

Dynamic allocation

NO

Institution consideration

Institution is not considered as adjustment factor.

Blocking

NO

Concealment

No need to know

No. of arms

3

Purpose of intervention

Prevention

Type of intervention

Food

Interventions/Control_1

Placebo condition: Participants received distilled water nasal spray during the second minute of the 80-W warm-up and at 25%, 50%, and 75% of the constant-power simulated 10-km cycling protocol. At each administration, two 0.2-mL actuations were delivered into each nostril, providing 0.8 mL per administration. The cumulative administered volume was 3.2 mL. This condition was completed once, with a 5-7-day washout period between trials.

Interventions/Control_2

15 mg/mL caffeine nasal spray condition: Participants received caffeine nasal spray at 15 mg/mL during the second minute of the 80-W warm-up and at 25%, 50%, and 75% of the constant-power simulated 10-km cycling protocol. At each administration, two 0.2-mL actuations were delivered into each nostril, providing 12 mg of caffeine per administration and a cumulative dose of 48 mg. This condition was completed once, with a 5-7-day washout period between trials.

Interventions/Control_3

20 mg/mL caffeine nasal spray condition: Participants received caffeine nasal spray at 20 mg/mL during the second minute of the 80-W warm-up and at 25%, 50%, and 75% of the constant-power simulated 10-km cycling protocol. At each administration, two 0.2-mL actuations were delivered into each nostril, providing 16 mg of caffeine per administration and a cumulative dose of 64 mg. This condition was completed once, with a 5-7-day washout period between trials.

Interventions/Control_4

Interventions/Control_5

Interventions/Control_6

Interventions/Control_7

Interventions/Control_8

Interventions/Control_9

Interventions/Control_10

Age-lower limit

18

years-old

<=

Age-upper limit

35

years-old

>=

Gender

Male

Key inclusion criteria

Healthy men aged 18-35 years.
Physically active participants or moderately trained cyclists.
Habitually performed exercise in a fasted state.
Able to complete the study procedures and provide written informed consent.

Key exclusion criteria

Cardiometabolic disease.
Nasal pathology.
Current smoking.
Recent musculoskeletal injury.
Habitual caffeine intake greater than 300 mg/day.
Use of supplements or medications likely to influence caffeine metabolism or the study outcomes.

Target sample size

28

Name of lead principal investigator

1st name	Hengzhi
Middle name
Last name	Deng

Organization

Universiti Malaya

Division name

Faculty of Sports and Exercise Science

Zip code

50603

Address

Jalan Universiti, 50603 Kuala Lumpur, Malaysia

TEL

60175885277

Email

s2198414@siswa.um.edu.my

Name of contact person

1st name	Hengzhi
Middle name
Last name	Deng

Organization

Universiti Malaya

Division name

Faculty of Sports and Exercise Science

Zip code

50603

Address

Jalan Universiti, 50603 Kuala Lumpur, Malaysia

TEL

60175885277

Homepage URL

Email

s2198414@siswa.um.edu.my

Institute

Universiti Malaya

Institute

Department

Personal name

Organization

Universiti Malaya Research University Grant

Organization

Division

Category of Funding Organization

Government offices of other countries

Nationality of Funding Organization

Co-sponsor

Name of secondary funder(s)

Organization

University of Malaya Research Ethics Committee - Non-Medical (UMREC-NM)

Address

Pusat Perkhidmatan Penyelidikan, Level 2, Kompleks Pengurusan Penyelidikan dan Inovasi, Universiti Malaya, 50603 Kuala Lumpur, Malaysia

Tel

+60 3 7967 7022 ext. 2369

Email

umrec@um.edu.my

Secondary IDs

NO

Study ID_1

Org. issuing International ID_1

Study ID_2

Org. issuing International ID_2

IND to MHLW

Institutions

Faculty of Sports and Exercise Science, Universiti Malaya (Kuala Lumpur, Malaysia)

Date of disclosure of the study information

2026

Year

10

Month

06

Day

URL releasing protocol

The study protocol is not publicly available.

Publication of results

Unpublished

URL related to results and publications

No external publication URL is currently available. Results are provided in this UMIN-CTR record.

Number of participants that the trial has enrolled

25

Results

Twenty-five men completed all three conditions. Compared with placebo, 15 and 20 mg/mL caffeine nasal spray increased mean cadence (102.6 vs 104.3 and 105.3 rpm) and shortened device-derived completion time (981 vs 964 and 955 s; all p < 0.05). Post-exercise incongruent Stroop reaction time was also shorter (758 vs 730 and 714 ms; both p < 0.05), without differences in accuracy. Plasma caffeine increased after both active conditions. No serious adverse events were reported.

Results date posted

2026

Year

10

Month

06

Day

Results Delayed

Results Delay Reason

Date of the first journal publication of results

Baseline Characteristics

Twenty-five healthy men completed the study, including 13 physically active participants and 12 moderately trained cyclists. Mean age was 25 +/- 4 years, height was 176.6 +/- 5.4 cm, body mass was 72.1 +/- 7.7 kg, and body mass index was 23.1 +/- 1.7 kg/m2. Mean peak oxygen uptake was 51.1 +/- 9.2 mL/kg/min, maximal power output was 277.7 +/- 62.9 W, and habitual caffeine intake was 85.0 +/- 62.3 mg/day.

Participant flow

Twenty-five participants were enrolled and completed the placebo, 15 mg/mL, and 20 mg/mL caffeine nasal spray conditions. All 25 participants were included in the cycling and cognitive analyses. Three participants declined blood sampling and two samples were excluded because of storage-related issues; therefore, plasma caffeine analyses included 20 participants.

Adverse events

No serious adverse events were reported. No clear caffeine-related differences in nasal, oral, gastrointestinal, neurological, muscular, or sleep-related side effects were identified during the acute trials or at the 24-hour follow-up.

Outcome measures

The primary outcome was mean self-selected cadence during the constant-power simulated 10-km cycling protocol. Mean cadence was higher with 15 mg/mL and 20 mg/mL caffeine nasal spray than with placebo (104.3 +/- 7.6 rpm and 105.3 +/- 7.4 rpm versus 102.6 +/- 7.6 rpm; both p < 0.05).

Secondary outcomes included device-derived completion time, Stroop reaction time and accuracy, plasma caffeine concentration, heart rate, rating of perceived exertion, and side effects. Device-derived completion time was shorter with 15 mg/mL and 20 mg/mL than with placebo (964 +/- 71 s and 955 +/- 73 s versus 981 +/- 75 s; both p < 0.05). Post-exercise incongruent Stroop reaction time was shorter with 15 mg/mL and 20 mg/mL than with placebo (730 +/- 66 ms and 714 +/- 72 ms versus 758 +/- 46 ms; both p < 0.05), without dose-related differences in accuracy. Post-exercise plasma caffeine concentrations were higher after both active conditions than after placebo and were higher after 20 mg/mL than after 15 mg/mL. Heart rate and perceived exertion showed no consistent dose-related effects.

Plan to share IPD

No

IPD sharing Plan description

Individual participant data will not be made publicly available because of privacy and ethical restrictions. De-identified data may be made available by the corresponding author upon reasonable request and subject to applicable ethical and institutional approval.

Recruitment status

Completed

Date of protocol fixation

2024

Year

12

Month

19

Day

Date of IRB

2025

Year

02

Month

15

Day

Anticipated trial start date

2025

Year

02

Month

15

Day

Last follow-up date

2025

Year

09

Month

19

Day

Date of closure to data entry

Date trial data considered complete

Date analysis concluded

Other related information

This study was retrospectively registered after completion of participant recruitment, data collection, and analysis. During the constant-power simulated 10-km cycling protocol, simulated distance was accumulated from flywheel revolutions. Device-derived completion time therefore depended on the self-selected cadence maintained during the protocol and should not be interpreted as conventional freely paced time-trial performance.

Registered date

2026

Year

10

Month

06

Day

Last modified on

2026

Year

10

Month

06

Day

Link to view the page

Value
https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000072332