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Introduction: Several studies have evaluated and confirmed the ergogenic effects of acute caffeine intake on sports performance. However, some studies suggest that this effect predominantly occurs in large muscle groups, potentially due to increased skeletal muscle electrical activity.
Objectives: This study aims to evaluate the acute effects of caffeine intake on strength, power, muscle endurance, and muscle electrical activity in young adults. It will also analyze the influence of circadian rhythms (morning vs. afternoon) on exercise performance (bench press vs. squat).
Methods: Twelve healthy, physically active participants will be recruited for the study. Using a triple-blind, crossover, randomized, and controlled design, participants will ingest either caffeine (3 mg/kg body mass) or a placebo (maltodextrin, 3 mg/kg) 60 minutes before the trial. Muscular strength, power, and endurance performance will then be assessed through 1RM tests, and at 25%, 50%, 75%, and 90% of 1RM, along with muscle endurance tests at 65% of 1RM, for both squat and bench press exercises. EMG will be used to measure skeletal muscle electrical activity during the tests. The experimental sessions will be conducted in the morning (8:00 am to 10:00 am) and the afternoon (4:30 pm to 6:30 pm).
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Caffeine - Morning | Experimental |
| |
| Caffeine - Evening | Experimental |
| |
| Placebo - Morning | Placebo Comparator |
| |
| Placebo - Evening | Placebo Comparator |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Caffeine | Dietary Supplement | Acute caffeine intake (3 mg/kg) |
|
| Measure | Description | Time Frame |
|---|---|---|
| Mean velocity at different %1RM | Measuring bar mean velocity desplacement during bench press and back squat exercises. | Through study completion, an average of 4 weeks |
| Peak velocity at different %1RM | Measuring bar peak velocity and time to reach peak velocity of bar desplacement during bench press and back squat exercises. | Through study completion, an average of 4 weeks |
| Mean power output at different %1RM | Measuring during bench press and back squat exercises. | Through study completion, an average of 4 weeks |
| Peak power output and time to reach peak power output at different %1RM | Measuring during bench press and back squat exercises. | Through study completion, an average of 4 weeks |
| Number of repetitions performed in 1 set at 65%1RM until task failure | Through study completion, an average of 4 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 4 weeks |
| Power output generated in 1 set at 65%1RM until task failure | In bench press and back squat exercise | Through study completion, an average of 4 weeks |
| Measure | Description | Time Frame |
|---|---|---|
| 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. | Through study completion, an average of 4 weeks |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Facultad de Medicina y Ciencias de la Salud. Universidad de Alcalá | Alcalá de Henares | Madrid | 28805 | Spain |
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| ID | Term |
|---|---|
| D002110 | Caffeine |
| ID | Term |
|---|---|
| D014970 | Xanthines |
| D000470 | Alkaloids |
| D006571 | Heterocyclic Compounds |
| D011688 | Purinones |
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Statistician
| Placebo | Dietary Supplement | Acute placebo intake (3 mg/kg of maltodextrin) |
|
| Muscle electrical activity (EMG). |
Root-mean-square (RMS) and maximal voluntary contraction (MVC) from pectoralis major and triceps (bench press) and from rectus femoris and vastus lateralis (Back squat). |
| Through study completion, an average of 4 weeks |
| Adverse effects | perception of power, endurance, energy and exertion, as well as heart, muscular and gastrointestinal discomfort. | Through study completion, an average of 4 weeks |
| D011687 |
| Purines |
| D006574 | Heterocyclic Compounds, 2-Ring |
| D000072471 | Heterocyclic Compounds, Fused-Ring |