In the previous posts we’ve discussed citrulline, beta alanine, and creatine. You can find those here if you missed them:
Today lets talk caffeine. Most people have had some sort of caffeine in their lives. It’s pervasive in many drinks from coffee to soda to energy drinks to gun etc etc etc.
No doubt many of you have heard people complain about needing their morning boost and how they can’t think or do anything or maybe they’re just in a bad mood until they get their coffee. Maybe you’re that person. At any rate caffeine is popular and has been so for a really long time.
Does it help the workout though? And is it safe? And can you have too much? There are lots of questions. I’m hoping to answer a few in this post.
First some biology 101. I know that may sound boring but it is much more interesting than organic chemistry. Trust me.
One effect caffeine is thought to exert in the body is the blockade of adenosine in the brain. Adenosine is a neurotransmitter that gives us feelings of sleepiness. Basically it tells us that maybe, just maybe it’s time to go lie down and get some Z’s. Researchers think caffeine exerts its wakefulness effects by blocking adenosine so that other neurotransmitters predominate. This in turn wakes us up.
So caffeine blocks adenosine which is like saying caffeine blocks our “go to sleep signals” in our brain. So far so good.
Like all chemical messengers adenosine has a receptor that it binds to send the signal, like a lock and key. This is where caffeine exerts its effect. By blocking the receptor adenosine can’t bind and transmit it chemical signal.
So caffeine blocks the adenosine receptor which stops adenosine’s signal. Ok still good.
The body doesn’t like it when things get out of balance. By not getting the signal for adenosine, the cells with those receptors upregulate them. It’s like little kids when they aren’t in sugar balance. You know, when kids yell and scream until they get enough sugar. So too do our cells scream they want more adenosine to keep the balance. (Maybe not the best example, but you get my drift)
After a few days of upregulation, more caffeine is needed to achieve the same effects as before. Many people notice this with chronic coffee consumption or other forms of caffeine. One shot espresso just doesn’t seem to cut it anymore and a double shot is needed. More receptors needs more caffeine to block them.
When caffeine isn’t ingested people feel incredibly sluggish and can’t seem to function at all. It’s because adenosine receptors are being met by all the adenosine and the sleep and rest signal is very strong. This is usually coupled with a nagging headache. Yup, use of caffeine regularly will cause this. And the only seeming cure is more caffeine.
Ok so that was today’s biology lesson. What about pre workouts you ask? Well….
Caffeine is definitely present in many preworkouts. Many. In fact it is probably the most used stimulant on the planet. This is the compound in pre workouts that give the boost of energy to really get rolling.
How effective is it?
A review of studies looking at endurance concluded that caffeine does increase endurance in time trial studies.  They reviewed 21 studies with 33 different treatments but only 15 had significant effects. The average mean improvement was 3.2%. Not a ton. There was quite a bit of variability between studies including ingestion times and types of exercise employed.
The researchers concluded that doses between 3-6mg/kg were the most effective while doses at 9mg/kg were no more effective and those may be potentially problematic, especially if consumed regularly. That range for a 75kg person is 225-450mg.
One study looking at these doses saw no difference between 3mg/kg and 6mg/kg but both were significant over placebo. 
In another study looking at 5mg/kg in users of caffeine (300mg/day) and non-users (<50mg/day), researchers found that non-users responded more favorably than users.  While the heart rate was significantly higher in the caffeine group, it was by 3-6 bpm higher than in the placebo group and to me doesn’t seem like a cause for concern. That is of course provided you don’t have any pre-exisiting heart conditions in which case I’d say stay away from caffeine.
These results lasted up to 6 hours in non users but were not seen for so long in the regular users.
Remember the adenosine we talked about earlier? It is this blockade of adenosine that seems to be the cause behind the better endurance, or at least perception of it according to the authors. 10 min after the start of exercise perceived exertion was significantly lower in the caffeine group than in the placebo group.
Perceived exertion was also less in the non-user group vs the user group which might indicate the idea of the receptor upregulation talked about. The authors concluded that although blood glucose was increased during exercise in the caffeine group, there wasn’t any evidence that the ergogenic effect of caffeine wasn’t from increase in fatty acid metabolism or utilization as has been previously thought.
What about muscle strength?
Caffeine has been tested on muscle strength in numerous studies. A meta analysis was done to see if there was overall a significant effect.  Researchers found that there was a significant increase in strength in knee extensors by about 7%. This effect wasn’t seen in other muscle groups. Endurance was also significant in open end point tests. In other words how long you could hold contraction vs intermittent contraction that you would normally see in regular activity. Doses ranged from 1mg/kg-9mg/kg.
In another study looking at the bench press, subjects were assessed as to their 1 rep max and then separated into placebo and caffeine groups. They were then asked to perform as many reps at 60% 1RM until failure. The caffeine group performed 22.4 +/- 3.0 reps vs 20.4 +/- 3.4 in the placebo group. They also lifted more weight, 1147.2 +/- 261.4 kg vs 1039.4 +/- 231.7 kg over placebo.  The dose used was 5mg/kg.
While the results of this study are significant I want to point out that most lifters don’t do one set to failure on bench and stop. While it’s certainly possible that this study could translate over into a more normal regimen of 3 sets of 10 or 5 sets of 5 we can’t be for sure based on this alone. After all if you do 3 sets of 10 reps spaced out with rest you are likely to achieve this same volume without caffeine or more.
In another review caffeine ingestion did increase some measures of sports teams performance. 11 of 17 studies showed beneficial effect of intake but it was more common in the well-trained athletes who hadn’t used caffeine.  The mean improvement was 6.5%.
In the strength portion the studies did also show significant improvement. Many endpoints were in the form of torque produced or total number of reps. There is some differences so it’s hard to gauge an overall effect and in what setting that caffeine will definitively produce results.
Other possible confounders are that these studies are free-living which means the subjects intake of food or supplements isn’t monitored. That always increases the chances that the results may be skewed.
It certainly does seem plausible however that caffeine could increase strength or power but the effect doesn’t seem to be as beneficial as with endurance, at least in my view.
Also because individuals are susceptible to caffeine at different levels, it’s hard to know if caffeine will actually make an individual perform better or not based on the studies. It’s like everything else with research; it tells us a good average, but where you as an individual fall on that continuum is up for debate.
While I know this review isn’t comprehensive, there does seem to be enough evidence for the use of caffeine in performance sports where endurance is required and may be beneficial in overcoming mental blocks. I do have a few words of caution.
Everyone is different but taking caffeine in the evening may not be a great idea if you don’t already. Some people will have little problem getting to sleep but others will be staring at the ceiling making friends with the thousands of sheep they’ll be counting trying to get to sleep.
Most studies with no effect were below 3mg/kg. Many that were at 3mg/kg saw positive outcomes as the 6mg/kg. In other words if this is something to try don’t start at 6mg/kg. Start at 3mg/kg and see what happens.
Also if you are a regular consumer of caffeine, you may need to back off completely from caffeine for a week or two to see any benefit at all. Caffeine intake probably needs to be cycled as well to maintain any benefit. If you do need to stop intake for a bit, it is probably wise to back off over a few days. A caffeine withdrawal headache might be in your future if you don’t.
People with abnormal heart rhythms would be wise to avoid caffeine, especially in the doses used for these studies. Caffeine is a stimulant and can cause big problems where small ones already exist.
Further caffeine can be taxing on the adrenals if higher doses are maintained over a period of time. This makes cycling a good idea. Be careful with anything that can stimulate your brain that has to be ingested. And having caffeine multiple times per day every day is probably not the best idea.
Disclaimer: All info on this website is for education purposes only. Any dietary or lifestyle changes that readers want to make should be done with the guidance of a competent medical practitioner. The author assumes no responsibility nor liability for the use or dissemination of this information. Anyone who chooses to apply this information for their own personal use does so at their own risk
1.Ganio, Matthew S., et al. “Effect of caffeine on sport-specific endurance performance: a systematic review.” The Journal of Strength & Conditioning Research 23.1 (2009): 315-324.
2.Desbrow, Ben, et al. “The effects of different doses of caffeine on endurance cycling time trial performance.” Journal of sports sciences 30.2 (2012): 115-120.
3.Bell, Douglas G., and Tom M. McLellan. “Exercise endurance 1, 3, and 6 h after caffeine ingestion in caffeine users and nonusers.” Journal of Applied Physiology 93.4 (2002): 1227-1234.
4.Warren, Gordon L., et al. “Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis.” Med Sci Sports Exerc 42.7 (2010): 1375-87.
5.Duncan, Michael J., and Samuel W. Oxford. “The effect of caffeine ingestion on mood state and bench press performance to failure.” The Journal of Strength & Conditioning Research 25.1 (2011): 178-185.
6.Astorino, Todd A., and Daniel W. Roberson. “Efficacy of acute caffeine ingestion for short-term high-intensity exercise performance: a systematic review.” The Journal of Strength & Conditioning Research 24.1 (2010): 257-265.