Effects of Hypoxia or Caffeine on 4km Time-trial Morning Cycling.
This study aims to implement a rigorously standardized protocol to investigate the effect of acute (60 min prior) caffeine intake or hypoxia (1000m and 2000m) on 4km time trial performance.
Study Overview
Status
Conditions
Detailed Description
Time-trial performance is widely regarded as the gold-standard measure of endurance exercise capacity, because successful performance depends on completing a fixed distance in the shortest possible time while effectively regulating pacing strategy and power output. As a result, time-trial performance is considered as one of the most ecologically valid measures of endurance performance in both laboratory investigations and applied sport settings. For many endurance athletes, training and competition frequently occur during the morning due to event scheduling, travel requirements and environmental considerations. However, the morning period is characterised by several time-of-day-related physiological differences that may negatively influence exercise performance. Although systematic reviews have reported substantial variability in the magnitude of diurnal fluctuations in time-trial performance, evidence from well-controlled laboratory studies using fixed-distance protocols under thermoneutral conditions consistently indicates superior performance during the late afternoon or evening. Specifically, improvements in evening performance have been observed across a range of endurance modalities, including 100-m swimming (2.6%), 1-km cycling (2.3%), 4-km cycling (2.6%), 10-km cycling (2.3%), 10-km treadmill running (6.3%), and 16.1-km cycling (3.6%). These findings suggest that morning time-trial performance may be compromised relative to later times-of-day, potentially due to circadian variations in physiological and psychological readiness for exercise. Given that athletes are often required to compete in the morning despite these potential limitations, identifying practical and effective strategies to enhance morning time-trial performance is of considerable interest to athletes, coaches and practitioners seeking to optimise competitive outcomes.
Among the nutritional strategies proposed to improve morning performance, acute caffeine ingestion remains one of the most widely consumed and extensively studied ergogenic aids. Caffeine (1,3,7-trimethylxanthine) primarily exerts its performance-enhancing effects through antagonism of adenosine receptors in the central nervous system, resulting in increased arousal, reduced perceptions of fatigue, and enhanced neurotransmitter activity, including dopamine and noradrenaline. These neurophysiological effects collectively promote wakefulness, attention and central motor drive, thereby facilitating exercise performance. Consistent with these mechanisms, substantial evidence demonstrates that caffeine can improve endurance exercise capacity and time-trial performance across a variety of exercise modalities. Despite the well-established ergogenic effects of caffeine, research examining its efficacy during morning time-trial exercise remains comparatively limited. Interpretation of the available literature is further complicated by several methodological shortcomings, including inconsistent caffeine dosing protocols, inadequate familiarisation procedures and poor control of habitual caffeine intake. Recognising the importance of habitual caffeine consumption as a moderator of physiological and performance responses, recent classification thresholds have been proposed. Categorising individuals as naïve (<25 mg·day-¹), low (25 mg·day-¹ to 0.99 mg·kg-¹·day-¹), mild (1.00-2.99 mg·kg-¹·day-¹), moderate (3.00-5.99 mg·kg-¹·day-¹), high (6.00-8.99 mg·kg-¹·day-¹), and very high (>9.00 mg·kg-¹·day-¹) caffeine consumers. Failure to adequately characterise and control habitual caffeine intake may therefore contribute to the variability observed across studies.
Additional methodological limitations within the existing literature include the absence of both placebo and no-pill comparator conditions, together with insufficient control of key chronobiological variables such as chronotype, sleep quality, habitual training time, and seasonal influences. These factors are particularly relevant given their established influence on exercise performance and their potential to confound assessments of both circadian variation and caffeine-related ergogenic effects. Indeed, recent systematic reviews have identified substantial methodological heterogeneity and risk of bias across chronobiology studies, highlighting the need for more rigorous and standardised experimental designs when investigating time-of-day effects on exercise performance. Consequently, well-controlled studies are required to determine whether acute caffeine ingestion can meaningfully attenuate the physiological disadvantages associated with morning endurance exercise and improve time-trial performance under ecologically valid conditions.
Therefore, the primary aim of the present study was to determine whether the ergogenic effects of acute caffeine (CAFF) ingestion, administered 60-min before exercise, enhance morning 4-km cycling time-trial performance when evaluated when behavioural, methodological and chronobiological confounders were carefully controlled. Habitual caffeine consumers with an intake of >150 mg·day-¹ were recruited to minimise the potential influence of caffeine tolerance and withdrawal, while maximising the physiological response to the administered 300 mg caffeine dose. Secondary outcomes included measures of core and skin temperature, ratings of perceived exertion (RPE), mood-state and physiological responses to exercise.
Study Type
Enrollment (Estimated)
Phase
- Phase 4
Contacts and Locations
Study Contact
- Name: Ben J Edwards, PhD
- Phone Number: 01519046238
- Email: B.J.Edwards@ljmu.ac.uk
Study Locations
-
-
Merseyside
-
Liverpool, Merseyside, United Kingdom, L3 3AF
- Recruiting
- Tom Reilly Building
-
Contact:
- Joao Agulhari, BSc
- Phone Number: 07379664724
- Email: jpagulhari@gmail.com
-
-
Participation Criteria
Eligibility Criteria
Ages Eligible for Study
Accepts Healthy Volunteers
Genders Eligible for Study
Description
Inclusion Criteria:
- Age: 18-30 years old
- Healthy (as determined by the pre-participation questionnaire)
- >2 years aerobically trained individuals
- Consume >150 mg/day of caffeine
- Be able to stick to the retiring and waking schedule of the study as well as no exercise 24 h before and no caffeine.
Exclusion Criteria:
- Age: <18 or >30 years old
- Consume <150 mg/day of caffeine hence caffeine naïve
- Those with a history of significant side effects after the consumption of caffeine.
- Deemed unhealthy/unable to perform exercise determined by PAR-Q
- Shift worker or having travelled out of the UK time zone within the last month of testing
- Muscle related injury or broken/fractured bone within the past 3 years Diagnosed sleep disorder
Study Plan
How is the study designed?
Design Details
- Primary Purpose: Other
- Allocation: Randomized
- Interventional Model: Crossover Assignment
- Masking: Double
Arms and Interventions
Participant Group / Arm |
Intervention / Treatment |
|---|---|
|
Experimental: ABCDE
Control, Placebo, Caffeine, 1000m, 2000m, |
300 mg of caffeine ingested in form of 3 100 mg capsules 60 minutes prior to testing.
Other Names:
Placebo capsules made to resemble caffeine. 3 pills the same size as caffeine but filled with maltodextrin (~1.6 g)
Other Names:
No pill control intended to act as a comparator for both Hypoxia and caffeine analysis
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 1000 m altitude.
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 2000 m altitude.
Other Names:
|
|
Experimental: BCDEA
Placebo, Caffeine, 1000m, 2000m, Control, |
300 mg of caffeine ingested in form of 3 100 mg capsules 60 minutes prior to testing.
Other Names:
Placebo capsules made to resemble caffeine. 3 pills the same size as caffeine but filled with maltodextrin (~1.6 g)
Other Names:
No pill control intended to act as a comparator for both Hypoxia and caffeine analysis
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 1000 m altitude.
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 2000 m altitude.
Other Names:
|
|
Experimental: CDEAB
Caffeine, 1000m, 2000m, Control, Placebo, |
300 mg of caffeine ingested in form of 3 100 mg capsules 60 minutes prior to testing.
Other Names:
Placebo capsules made to resemble caffeine. 3 pills the same size as caffeine but filled with maltodextrin (~1.6 g)
Other Names:
No pill control intended to act as a comparator for both Hypoxia and caffeine analysis
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 1000 m altitude.
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 2000 m altitude.
Other Names:
|
|
Experimental: DEABC
2000m, Control, Placebo, Caffeine, 1000m, |
300 mg of caffeine ingested in form of 3 100 mg capsules 60 minutes prior to testing.
Other Names:
Placebo capsules made to resemble caffeine. 3 pills the same size as caffeine but filled with maltodextrin (~1.6 g)
Other Names:
No pill control intended to act as a comparator for both Hypoxia and caffeine analysis
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 1000 m altitude.
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 2000 m altitude.
Other Names:
|
|
Experimental: EABCD
1000m, 2000m, Control, Placebo, Caffeine, Caffeine, |
300 mg of caffeine ingested in form of 3 100 mg capsules 60 minutes prior to testing.
Other Names:
Placebo capsules made to resemble caffeine. 3 pills the same size as caffeine but filled with maltodextrin (~1.6 g)
Other Names:
No pill control intended to act as a comparator for both Hypoxia and caffeine analysis
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 1000 m altitude.
Other Names:
Hypoxia intervention ran in a controlled environmental chamber on site. Set oxygen partial concentration to similar levels at 2000 m altitude.
Other Names:
|
What is the study measuring?
Primary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
4km time to completion
Time Frame: 5 weeks
|
How long does the participant take to complete 4km cycling |
5 weeks
|
|
Average power
Time Frame: 5 weekas
|
Average power sustained through the 4km |
5 weekas
|
Secondary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
Cognitive function
Time Frame: 5 weeks
|
Stroop word-colour interference test |
5 weeks
|
|
Witty
Time Frame: 5 weeks
|
Light reaction test |
5 weeks
|
|
Memory test
Time Frame: 5 weeks
|
Rey's Auditory Verbal Learning test |
5 weeks
|
Collaborators and Investigators
Sponsor
Study record dates
Study Major Dates
Study Start (Estimated)
Primary Completion (Estimated)
Study Completion (Estimated)
Study Registration Dates
First Submitted
First Submitted That Met QC Criteria
First Posted (Actual)
Study Record Updates
Last Update Posted (Actual)
Last Update Submitted That Met QC Criteria
Last Verified
More Information
Terms related to this study
Keywords
Additional Relevant MeSH Terms
- Signs and Symptoms, Respiratory
- Pathological Conditions, Signs and Symptoms
- Signs and Symptoms
- Hypoxia
- Sulfur Compounds
- Organic Chemicals
- Heterocyclic Compounds
- Heterocyclic Compounds, 2-Ring
- Heterocyclic Compounds, Fused-Ring
- Carboxylic Acids
- Alkaloids
- Anilides
- Amides
- Aniline Compounds
- Amines
- Acetanilides
- Purinones
- Purines
- Acids, Carbocyclic
- beta-Lactams
- Lactams
- Cephalosporins
- Thiazines
- Phenylpropionates
- Xanthines
- Acetaminophen
- Caffeine
- Ibuprofen
- Cephalexin
- 2-(3',4'-dihydroxyphenyl)ethylene sulfate
- 5'-palmitoyl cytarabine
- temoporfin-polyethylene glycol conjugate
Other Study ID Numbers
- 261020LJMUSPSREC348
Plan for Individual participant data (IPD)
Plan to Share Individual Participant Data (IPD)?
Drug and device information, study documents
Studies a U.S. FDA-regulated drug product
Studies a U.S. FDA-regulated device product
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