Does caffeine effect physical performance? Think about pre-workout supplements having caffeine as a major ingredient. Perhaps, chugging a few cups of coffee can, after all, keep you going for that extra mile.
Numerous scientific studies have been conducted, in the quest of a definitive answer about its use by athletes and sports enthusiasts, to see how caffeine affects endurance performance, strength performance, and other forms of physical activities. 
So, let us see how exactly caffeine influences physical performance.
How soon can you see the effects of caffeine?
When you consume caffeine, most of it is quickly absorbed from the GI tract into the bloodstream within the next 45 minutes. It can take anywhere from 15 to 120 minutes to reach maximum levels in the bloodstream. So, you can commonly see its influence on performance within an hour after consumption.
Significant levels are maintained for 3 to 5 hours, after which they begin to reduce. 
The effect of caffeine varies from person to person. Some people are more sensitive to caffeine and get influenced with only a small dose while others may need 3 cups of coffee to see results.
How does caffeine affect the body?
Caffeine does not affect just a single aspect of the body. It can circulate through body water. It has the capability to affect cells throughout the body. It is lipophilic, meaning that it can enter all biological cell membranes and can even enter the brain easily. 
The following are a few ways caffeine’s influence at the cellular level translates itself into better performance.
Inhibition of Adenosine Receptors
Caffeine primarily stimulates the central nervous system by inhibiting adenosine receptors in the brain. [2, 3] It acts as a competitor to adenosine and binds the receptors, causing a dominance of its influence in place of the sleep-inducing adenosine. It, thus, causes an increase in alertness.
Studies suggest that caffeine’s performance enhancing functions attribute to this action of it influencing adenosine receptors. Caffeine influences the brain and enhances energy and focus, while reducing the feeling of fatigue.  So, a cup of coffee some time before your workout can boost the productivity of the workout.
Indirect effects of Adenosine inhibition
Adenosine inhibition indirectly affects the release of other brain chemicals including dopamine, norepinephrine, serotonin, etc., which again have their share of influence on alertness and happiness.
These helps in increasing the feeling of enjoyment and make exercise feel fun.
Similarly, caffeine motivates the release of adrenaline, the fight and flight hormone, which enhances performance levels. It was found that greater doses of caffeine had the greatest effect on epinephrine or adrenaline production while low doses had no significant effect. 
Effect on Metabolism
Various studies have proven that caffeine aids the process of burning fat through lipolysis, which refers to the breakdown of fat in fat cells. During this process, the body releases free fatty acids into the blood and converts fat into energy. [6, 7]
Consuming coffee before a workout, can thus, enable you to burn more fat, thus increasing the output of activities like endurance sports.
Increase in body temperature
Caffeine has found to increase the body’s heat generation or thermogenesis.  This, again increases the rate of metabolism and helps burn more calories, making your workout session more productive.
Muscle pain reduction
Caffeine affects the motor cortex, a part of the brain that is responsible for muscle activation. Caffeine works by reducing perception of pain in the muscles.
A study found that caffeine increased muscle torque and muscle activity during strength training. The study saw that participants who consumed caffeine outperformed those who did not. 
Release of Endorphins
Caffeine also affects the release of beta-endorphins, which are responsible for the feeling of alertness.
So, a cup of coffee can help you feel a more of the exercise-high, which is a common outcome of a workout session.
Increased levels of glycogen in muscles
When consumed along with carbs after a workout, caffeine has the influence of enhanced rates of glycogen re-synthesis in the muscles. A study showed that people who consumed caffeine with carbs following a vigorous exercise routine had 66 percent more glycogen in the muscles compared to those who consumed just carbs. 
This results in easy and quicker muscle recovery after sports and leads to better performance the following day.
Caffeine in Endurance Sports
Endurance athletes are unsurprisingly in the search of methods that enhance performance. Caffeine is a natural stimulant that is widely used by athletes prior to their activity.
It is seen that caffeine does enhance performance in endurance sports, both short 5-minute activities and in longer sports.
Shorter activities were benefited due to a few interrelated neuro-muscular effects of caffeine. Longer activities can harness many benefits of caffeine including reduced perception of effort and fatigue, greater focus, reduced glycogenesis, and increased metabolism. 
Studies were conducted to see its effects in various sports including running, swimming, and cycling. 
Caffeine in High-intensity Exercise
Mixed results have been seen with the use of caffeine for high-intensity exercises.
Most studies have pointed a significant improvement in athletes who are well-trained. On the other hand, studies on beginners or untrained athletes have shown no effects of caffeine consumption.
Caffeine in Strength Training
Research indicates that caffeine may enhance muscular strength and endurance.
This study shows that the improved strength appeared mostly in knee extensors. 
Another study showed that caffeine showed improvement in muscle strength irrespective of the location of the muscle group. 
The results of these and other similar studies, however, are not conclusive and more research in the area is expected to make things clearer.
Are there any adverse effects of caffeine?
When consumed in moderation, caffeine has more benefits and minimal side-effects, if any.
However, a few health conditions may be aggravated by caffeine.
People with high blood pressure and heart conditions should not consume caffeine. Caffeine can increase blood pressure, and when combined with exercise, which also increases blood pressure, may cause problems in patients already suffering from hypertension.
Caffeine may also intervene with certain medications. People who are susceptible to anxiety may prefer avoiding high doses of caffeine.
It is important to consult your doctor before taking supplements with caffeine in it and using caffeine for sports.
To be safe, check the quantity of caffeine in pre-workout supplements. Some of them have very high doses like 400 mg of caffeine, which may be dangerous in combination with other dietary sources of caffeine.
Excessive caffeine may cause symptoms like:
- Increase in heart rate
- Abdominal discomfort
Because of caffeine’s role in disrupting sleep, it is a good idea not to consume foods and drinks with caffeine late at night, especially within 3 – 4 hours before bedtime, so that the circadian rhythm of the body is not disturbed.
How much is too much?
The maximum recommended level of caffeine is 400 mg per day, which is as good as 4 cups of coffee a day. 
Optimal dosage of caffeine is varied for everyone. The commonly used dosage ranges between 3 to 6 mg per kg of body weight.
Low doses have also shown to have effects on performance enhancement. So, start low and test your tolerance before you increase your dose.
Habituated to Coffee? Doesn’t Matter.
Contrary to what was previously believed, recent research says that the effect of caffeine does not reduce due to habituation. So, even if you are a regular coffee drinker, you can still reap the effects of coffee. 
Coffee is diuretic? – Another Coffee Myth
It was believed that coffee is diuretic and dehydrating.
However, this turns out to be a myth.
The belief stems from studies conducted with a couple of hours after caffeine consumption. When studies took a full day into account, it was seen that there was no dehydration.
Thus, a cup of coffee can count as a regular fluid. 
The Bottom Line
The next time you drink your coffee and feel more alert, you know the reason! The caffeine in coffee has a direct influence on the brain. So, you can utilize the benefits of coffee to train longer, burn more fat, and enjoy your exercise, knowing also, that you will be much less bothered by muscle pain.
Remember to ensure you are consuming safe levels, though!