Caffeine is the most widely used drug, with 90% of U.S. adults consuming at least one caffeinated meal or beverage every day. Many people use caffeine to help stay awake in the early hours of the morning, or to help stay focused when their attention starts drifting at work. Caffeine is a stimulant, which means when ingested it excites the brain and nervous system. This is why caffeine is responsible for giving us that jolt of energy. What role does caffeine play in exercise performance?
How Does Caffeine Affect Exercise?
Many people consume caffeine pre-workout because it helps them exercise at a higher intensity with less fatigue. Adenosine is a special molecule in the body that, when attached to adenosine receptors, is what is responsible for making you feel tired or drowsy. When caffeine is ingested it counteracts this process by binding to those same adenosine receptor sites. In other words, caffeine and adenosine play musical chairs for the same receptor sites, and when absorbed caffeine stimulates, instead of depressing, the nervous system.1,2
1) Moderately Increase Fat Metabolism and Mobilization.
Studies show those same adenosine receptor sites inhibit hormones responsible for fat metabolism, and when caffeine is absorbed this hormone-inhibiting effect disappears.2 This fat-metabolizing effect is why the main ingredient in fat-burners is usually caffeine. It should be noted, however, that caffeine’s ability to metabolize fat is negligible compared to other strategies (i.e. caloric deficit and proper macronutrient proportions).
2) Improved Endurance Performance
Endurance performance appears to be the strongest benefit of pre-workout caffeine ingestion. Studies have shown improvements of 10-20% in time-to-exhaustion for endurance activities.2,3 This means it would take a little bit longer for you to feel tired during your workout than you normally would without consuming caffeine.
3) Improved Psychological Benefits
Research participants supplementing with caffeine rated exercise as less strenuous and less painful compared to the placebo.4 The discomfort of exercise is one of the biggest reasons so many people avoid regular exercise. If caffeine can reduce these feelings of discomfort, then perhaps it can lead to increased motivation and consistency.
4) Acutely Improves Strength for Resistance Training
Caffeine can improve resistance training performance by increasing the motor unit recruitment of the muscles—allowing the individual to produce more force. Consuming more than 6mg/kg of bodyweight does not improve the performance-enhancing benefits of caffeine.2 This equates to an upper limit of about 350mg of caffeine for a 130lb female, and 500mg for an 180lb male. Any caffeine ingestion beyond this limit provides no additional benefit and could lead to harmful side effects.
Caffeine Dependence: Too Much of a Good Thing?
Most healthy adults without any health issues can safely consume about 400mg of caffeine without any negative side effects. Like any other psychoactive drug, regular consumption of caffeine can lead to symptoms of dependency.5 When someone who is caffeine-dependant stops consuming caffeine, these are some of the symptoms they could experience:
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Additionally, those individuals who may have prior health concerns, such as heart disease, type 2 diabetes, or women who are pregnant or nursing, should limit their caffeine intake to no more than 300mg per day.6 If using caffeine prior to exercise, it should be taken approximately 15-30min before the start of your workout. For most people (those not overly-sensitive to caffeine) the effects will wear off within a couple hours.
Caffeine is commonly used across the globe to help improve cognitive function and physical performance. Caffeine, just like any other drug, should be used cautiously and only in the recommended doses. Additionally, while caffeine can improve a variety of exercise-related variables, there is an upper limit in which no more positive benefit is seen and overconsumption can lead to many negative side effects. Individuals with pre-existing health concerns should speak to their doctor before supplementing with caffeine.
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