Caffeine — Can It Really Jack You Up?

May 2, 2012

Dwayne N. Jackson, PhD

For thousands of years, caffeine, a bitter-tasting psychoactive stimulant, has made its way into our diet in many forms. It occurs naturally in a variety of plants and seeds, serving as a natural pesticide that paralyzes and kills many insect species. As far back as the Stone Age, it was found that chewing the seeds, bark or leaves of certain plants elevated mood, increased energy level and focus, and decreased hunger. It wasn’t until more recently that researchers discovered these effects were due to caffeine. 

Today, caffeine is regarded as the most “widely enjoyed” psychoactive substance and is ingested daily by 90% of North Americans. Caffeine is an ingredient in numerous over-the-counter medications and exists in coffee, tea, cola, chocolate, energy drinks, medications and many other products. 

In the past decade there has been an explosion in the number of scientific studies investigating the ergogenic potential of caffeine. Most of these investigations have demonstrated that caffeine can give a significant performance-enhancing edge via different mechanisms. In response, several sports governing bodies have placed restrictions on the use of caffeine in athletes. Just how big a boost can caffeine give? Let’s look at the latest scientific evidence to illustrate how caffeine can augment your day-to-day workouts and your long-term muscular development. 

Mechanisms of Action

When you ingest caffeine, it acts on two levels: centrally (in the brain) and peripherally (in the body). Centrally, caffeine is a central nervous system stimulant that non-selectively blocks adenosine receptors. In the brain, adenosine binds to nerve cells and makes them slow their activity. Caffeine is structured much like adenosine, so nerve cells readily allow caffeine to bind to their adenosine receptors, thus blocking the inhibitory action of adenosine on nerve activity. As such, the caffeinated brain is chock-full of hyperactive nerve cells, an environment perceived by the pituitary as an emergency that results in adrenaline release from the anterior pituitary. As well, caffeine intake results in increased dopamine levels in the brain, giving the user a sense of well-being. 

In the periphery, caffeine inhibits an enzyme called phosphodiesterase (PDE). In cells PDE works to break down cyclic adenosine monophosphate (cAMP). cAMP is a very important cell-signaling substance (called a second messenger), and caffeine stops the breakdown of cAMP. As such, cAMP levels build up, which prolongs and intensifies neurotransmitter and hormonal effects. 

The net result of caffeine ingestion is increased release of norepinephrine (noradrenaline) from sympathetic nerves, elevated adrenaline release from the adrenal medulla and higher dopamine signaling in the basal ganglia. These outcomes in turn cause an increase in the rate and force of heart contractions, constriction of blood vessels, dilation of the airways and pupils, and increased fat mobilization. All in all, your body ends up more alert and primed for action. 

Caffeine’s Effects on Health

The impact of caffeine on health has been a subject of debate for years. Many medical professionals warn against heavy caffeine consumption because of its addictive potential and stimulant effects. Early reports warned that caffeine might lead to cardiovascular disease and hypertension because blood pressure rises with moderate ingestion. However, scientists at Harvard University (Cambridge, MA) determined that drinking more than six cups of coffee per day (totaling 500–600 milligrams of caffeine) didn’t increase cardiovascular risk. In fact, a very recent study from Brooklyn College (NY) reported that men who drank four cups of coffee per day had 53% less risk of dying from cardiovascular disease than those who abstained. 

There are several lines of evidence demonstrating that caffeine in moderation provides many benefits to overall health. For example, as little as one dose (a cup of coffee or 100 milligrams of caffeine) has been shown to improve airway function for up to four hours in people with asthma. As well, it has been demonstrated that men who drink four cups of caffeinated coffee per day reduce their chances of developing Parkinson’s disease by about 50%, likely a result of increased dopamine signaling in the basal ganglia. In addition, daily caffeine improves short-term memory and brain function. 

Bodybuilding Effects

In a recent double-blind, placebo-controlled study from the University of Georgia (Athens) it was found that caffeine ingestion (approximately 300 milligrams) before maximal voluntary isometric contraction reduced muscular pain intensity by almost 50%! It’s hypothesized that this dramatic decrease in muscular pain is because of caffeine’s ability to block adenosine receptors in the brain and spinal cord involved in pain processing and perception. To put this finding into perspective, a study concluded that the nonsteroidal anti-inflammatory and analgesic Naproxen had only a 30% reduction in post-exercise muscle soreness. This research suggests that you can push your muscles further and harder with each workout when taking caffeine, thus providing a greater stimulus for growth. 


Several lines of evidence show that caffeine ingested before a workout increases anaerobic strength. For example, a recent study published in the Journal of Strength and Conditioning illustrate that consuming caffeine one hour before training increased bench press 1RM strength better than a placebo. In support, an earlier study indicated that caffeine supplementation increased knee extension and flexion power and strength in elite athletes. It must be noted that this effect may be realized only among trained individuals, as a recent report showed that caffeine ingestion in untrained subjects resulted in no increase in 1RM bench-press strength. 

Fat Loss 

Ingestion of caffeine prior to low-intensity aerobic exercise has been scientifically demonstrated to boost lipolysis (fat burning). This significant fat-burning effect is based on two scientifically known mechanisms. First, there’s a synergistic increase in norepinephrine (noradrenaline) and epinephrine (adrenaline) release associated with the combination of exercise and caffeine supplementation. Norepinephrine is a key regulator of fatty acid release from fat cells into blood circulation to be burned for energy. Second, caffeine competes with adenosine on adenosine receptors in fat cells. Under normal conditions, adenosine binds to fat cells and decreases the release of fatty acids. Therefore, taking caffeine blocks this inhibitory effect of adenosine on fatty acid release, resulting in greater fat mobilization and availability for metabolism. 


Since caffeine is a well-documented central nervous system stimulant, it’s no surprise that it has profound positive effects on energy and focus (like most stimulants). A recent meta-analysis published in the Scandinavian Journal of Medicine and Science in Sports has shown that caffeine dampened perceived exertion during and after exercise by 5.6% compared to a placebo. Ingesting caffeine before a workout has been shown to significantly improve endurance in aerobic and anaerobic sports. It has been postulated that aerobic performances benefit from increased free fatty acid mobilization, thus improving time to exhaustion. However, for short-duration anaerobic performances (like weight training), scientists speculate that the caffeine-induced increase in dopamine signaling in the basal ganglia has the greatest effect on time to exhaustion. Nonetheless, all of this means you can push harder, for longer by ingesting caffeine before training. 


Australian scientists have found that caffeine boosts muscle glycogen recovery post-exercise. In a recent article published in the Journal of Applied Physiology, it was shown that ingestion of high dosages of caffeine and high-glycemic carbohydrates (i.e., fast sugars) immediately after training results in 66% greater glycogen repletion than carbs alone. In fact, the authors concluded that the augmented rate of glycogen repletion observed in their study was the highest ever reported in humans under normal physiological conditions. The scientists also noted that throughout a four-hour recovery period, those who ingested caffeine with carbohydrates had much higher levels of insulin and blood glucose, a potent signal for anabolic drive. As well, it has been shown that athletes who took about 200 milligrams of caffeine before eccentric exercise had a large reduction in pain afterward and much less delayed-onset muscle soreness (DOMS). 

Obviously, the scientific support for caffeine supplementation in bodybuilding is convincing. In fact, most of you likely take a form of caffeine before you work out and have already noted its great benefits. 

Consuming Caffeine Wisely

Based on the scientific evidence, there are a few facts you need to know before taking caffeine to enhance your workouts. 

  1. More is not better; in fact (as with most stimulants), the benefits of caffeine diminish if more than an optimal dose is taken. In science this is called the inverted-U effect. 
  2. Caffeine can dehydrate you (it’s a diuretic), so you should increase your water consumption when taking it. 
  3. Caffeine has a relatively long half-life of six hours. If you drink a large coffee (with about 200 milligrams of caffeine) at 6 p.m. before you work out, you will still have 100 milligrams active in your body at midnight. This can severely impact your sleep cycle, and sleep is of primary importance to strength and muscular gains. 
  4. Caffeine is addictive! Use it in moderation and don’t use it to make up for poor sleep habits. 

How to Use Caffeine 

Based on the scientific literature, one point is clear: You can reap all the benefits of caffeine supplementation by taking it an hour before working out. However, the dose of caffeine needed to produce an ergogenic effect isn’t set in stone (i.e., single doses can range from 200–700 milligrams). If you’ve never consumed caffeine as part of your supplementation regimen, start with the lowest dose and work up accordingly. If you experience symptoms like shaking, nervousness, heart palpitations or anxiety, you’ve taken too much. 

For optimal results

Take 2 equal daily doses, each 100–300 milligrams. Take one dose upon waking and the other dose one hour before training. 


The most reliable source is the tablet form of caffeine anhydrous; tablets are dosed accurately and can be split to meet your requirements and tolerance. Other sources will have significant variability in dose and purity. Also, some products can have tons of sugar (like soda pop) and/or fat (like fancy coffee beverages) that can blunt your workout goals. For caffeine content among common beverages, see the “Drink Up” chart below. 

One last reminder  

Don’t take caffeine if you have a known sensitivity to stimulants or if you’ve been diagnosed with cardiovascular disease. 


Here is a chart of common caffeine sources and their approximate caffeine contents. 

Source and Caffeine Content Rockstar Zero-Carb (16 oz.) 160 mg Monster Lo-Carb (16 oz.) 160 mg Brewed coffee (1 cup) 60–165 mg Double espresso (2 oz.) 45–100 mg Red Bull Sugar-Free (8 oz.) 75 mg Instant coffee (1 cup) 70 mg Tea (1 cup) 40 mg Diet Coke (12 oz.) 45 mg