A supplement that actually works to boost performance consistently is a rare find. So when a substance like caffeine is found to routinely work, be safe in the doses prescribed, be readily available, and is, most importantly, legal, it is almost a no brainer to pop some caffeine before those hard workouts and races to get a nice little edge. But is performance improvement always a good thing or does it come at a cost?
Caffeine itself generally improves performance through two known mechanisms, as a Central Nervous System (CNS) stimulant and by enhancing muscle contraction itself. As a CNS stimulant, performance is increased via alterations in pain perception and by an increase in the pain threshold. Essentially you are loosening the strings of the governor your body uses to hold you back from pushing too far and doing yourself more harm than good. The caffeine shifts the balance a bit, making your body feel like it’s not working as hard and being able to delve a tad deeper. From a muscle contraction standpoint, caffeine enhances the ability of the muscle itself to work via modulating calcium release, which is a crucial factor in the whole process. The bottom line is that it works! So what’s wrong with that?
The answer is nothing in the short term and if the purpose is a one-off race that you want to hit. The problem we run into is that it can quickly fall into that old “too much of a good thing” slogan. The same mechanisms that increase performance acutely can wreak some havoc on your body if the situation becomes chronic. Hard workouts or races also tax the CNS. So, in theory, if caffeine is constantly stimulating the CNS and modulating the body’s CNS response to the stress of exercise, then you can have a double whammy effect of you becoming dependent on stimulating the CNS to get through a certain workout. Essentially, the caffeine ingestion becomes the norm, and those safeguards that might tell you to back off for a certain workout are ignored or drowned out by drug-induced happiness to the body. Fatigue is just a way of your body telling you there’s some issue and if you ignore it constantly, chronic fatigue could be in your future. An example of how the perception of fatigue can be modulated can be seen in studies looking at caffeine consumption in everyday life. For those who rely on that morning coffee every day, the research shows that the morning caffeine isn’t actually providing any sort of boost in terms of energy. Instead, the caffeine just brings a person back up to normal and the tiredness and fatigue is a result of withdrawal from not getting that fix during the hours that they have slept. That’s a pretty powerful statement if we think about how “norms” are completely changed by chronic caffeine consumption.
Similarly, what happens to your immune system when you consume caffeine and then go work out is also different. Recent research has found that caffeine actually boosts the activation of antigen-stimulated NK-cells, which are the cells that regulate your innate immunity. Your innate immune system is essentially the generic built-in response to any number of triggers. This is generally a good thing, so what’s the problem? The same research found that the other big players in the immune system–cells called antigen-stimulated T-cells–are decreased when caffeine and exercise are combined. These cells are part of what is called your adaptive immune system, which is best thought of as your specific immune system defenders which provides a tailored specific response. The problem then becomes that if you constantly run down your adaptive immune system, the susceptibility to sickness, disease, or any other component of having a weakened immune system would be increased.
What we’re left with is a substance that definitely improves performance, but might have some drawbacks that most don’t consider. In terms of performance enhancement for your running I think the answer is quite simple: save the caffeine for when you need it. Don’t use it for every workout because in the end it doesn’t matter if you hit your mile repeats one second faster if the eventual drawback is some sort of chronic fatigue that comes back to bite you. Instead, save it for when it matters most: race day.
By: Steve Magness
Steve Magness coaches professional runners alongside Alberto Salazar at the Nike Oregon Project. He also maintains the blog ScienceOfRunning.com which is essentially a place for him to display his inner science and running nerd to the world. He owns a best of 4:01 for the mile and has a M.S. in Exercise Science from George Mason University.