Caffeine, Resistance Exercise and EMG

Effect of Acute Caffeine Intake on Muscle Electrical Activity and Muscular Strength, Power, and Endurance Performance

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).

Study Overview

• Status: Completed
• Conditions: Caffeine
• Intervention / Treatment: Dietary supplement: Caffeine; Dietary supplement: Placebo

• Study Type: Interventional
• Enrollment (Actual): 12
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Spain
  • Madrid
    • Alcalá de Henares, Madrid, Spain, 28805
      • Facultad de Medicina y Ciencias de la Salud. Universidad de Alcalá

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• 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.

Exclusion Criteria:

• 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 after 6 pm on the day before the tests, to avoid headaches, discomfort, or lethargy in regular caffeine consumers.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Caffeine - Morning	Dietary supplement: Caffeine; Acute caffeine intake (3 mg/kg)
Experimental: Caffeine - Evening	Dietary supplement: Caffeine; Acute caffeine intake (3 mg/kg)
Placebo Comparator: Placebo - Morning	Dietary supplement: Placebo; Acute placebo intake (3 mg/kg of maltodextrin)
Placebo Comparator: Placebo - Evening	Dietary supplement: Placebo; Acute placebo intake (3 mg/kg of maltodextrin)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	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
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

Secondary Outcome Measures

Outcome Measure	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
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

Collaborators and Investigators

• Sponsor: University of Alcala

Study record dates

Study Major Dates

• Study Start (Actual): September 1, 2023
• Primary Completion (Actual): April 30, 2024
• Study Completion (Actual): April 30, 2024

Study Registration Dates

• First Submitted: September 9, 2024
• First Submitted That Met QC Criteria: September 18, 2024
• First Posted (Actual): September 23, 2024

Study Record Updates

• Last Update Posted (Actual): September 23, 2024
• Last Update Submitted That Met QC Criteria: September 18, 2024
• Last Verified: September 1, 2024

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Enzyme Inhibitors; Purinergic Antagonists; Purinergic Agents; Phosphodiesterase Inhibitors; Purinergic P1 Receptor Antagonists; Central Nervous System Stimulants; Caffeine
• Other Study ID Numbers: CEIP/2023/4/093_2

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No