Quantifying the placebo effect in sports performance

Last month, I wrote about how the coach may act as a placebo, potentially exerting performance enhancing effects through a variety of means. The research discussed in that article was just s small part of recent efforts to better understand the influence of placebo effects on sporting performance. An upcoming special issue of European Journal of Sports Science aims to dig even more into the area, including another paper on the potential to further enhance our understanding of how placebo can affect performance.

The placebo effect of ergogenic aids

The latest paper is an exploration of how ergogenic aids, including nutritional supplements and mechanical aids, potentially enhance sporting performance via placebo effects. The study design is that of a systematic review, where the authors scour the research to date for relevant studies, and then pool the results to provide a summation of the current research. In this case, the authors were specifically interested in studies of ergogenic aids that utilized an intervention trial, a placebo trial, and a no-treatment control trial. This is important; whilst much research often compares an intervention to a placebo—in part to protect against the influence of placebo effects on the study outcome—these authors were more interested comparing the results of the placebo trial with the no-placebo control trial, to quantify the magnitude of the placebo effects on performance.

To give an example, if researchers want to explore the efficacy of caffeine tablets, often they will run two trials; in one, the subjects consume caffeine tablets, in another, the subjects consume identical-looking tablets that contain no caffeine. If the researchers of this caffeine tablet study also included a trial in which the subjects consumed no tablets at all, it would have been included in this systematic review. In total, 32 studies met the inclusion criteria; 20 explored nutritional ergogenic aids, and 12 explored mechanical ergogenic aids.

How large is the placebo effect on sports performance?

Of the nutritional ergogenic aids, caffeine was the most well-studied. The body of research in this area showed that, when subjects believed they had consumed caffeine but had actually consumed a placebo, their performance improved. The size of this improvement was, in some cases, quite large. An effect size of around 0.2 is considered to be the benchmark of an intervention being worthwhile; one study reported an effect size of 0.82 for placebo caffeine.

Additionally, in most cases, if subjects are given a placebo that they believe is a placebo, their performance actually gets worse. For sodium bicarbonate, a single study gave some interesting results; both sodium bicarbonate, and placebo where the subjects believed they had consumed sodium bicarbonate, enhanced performance by about the same amount (1.7% vs 1.5%). However, when the subjects were given sodium bicarbonate, but thought it was a placebo, there performance actually decreased! This demonstrates that an athlete’s belief as to whether or not they have consumed something that is performance enhancing is a large part of whether a given supplement “works.”

Some of my favorite placebo studies utilized substances purported to be performance enhancing drugs, but are actually inert. In one study, well-trained powerlifters got substantially stronger following eight weeks of placebo ingestion, which they believed were anabolic steroids. As soon as they were told that their “drugs” were, in fact, placebo, their strength training performance immediately returned to baseline.

The placebo effects are not just limited to nutritional ergogenic aids: in one study, a group of participants were given a tennis racket that they believed would enhance their serving performance—but was just a standard tennis racket. Their average serving speed improved by over 5%, again demonstrating that, if you think something is performance enhancing, that may be enough to enhance performance.

Takeaways for coaches

So, what does all of this mean for coaches? Firstly, it’s important to state up front that many of the leading researchers in this area believe that it is unethical to deceptively administer placebos to athletes; that you shouldn’t give your athletes something inert, and then tell them that it is performance enhancing. This is especially true given the strict liability policy of WADA – in fact, you shouldn’t be giving your athletes any supplements at all. However, an important aspect, and following on from my previous article, is that if an athlete does not fully believe in a certain process, then their performance improvement is likely to be reduced compared to an athlete who does strongly believe. The opposite is also true; belief that something is performance enhancing, when in reality it isn’t, may also enhance performance.

To me, this indicates that, if an athlete believes in something, providing it is not potentially harmful or performance limiting, it might be best to allow them to continue. More broadly, this could be a specific exercise that the athlete likes to do in a warm-up; whilst you might not see the relevance of the exercise, if that athlete thinks it’s important, then arguably you should let them do it. Furthermore, if an athlete is engaging in a behavior that has clear performance enhancing potential, then you should try to maximize a positive belief in this behavior. For example, if an athlete is interested in utilizing caffeine pre-race, then re-enforcement from a coach as to caffeine’s performance benefits may further enhance its ergogenic potential.

The complexity of progress

Bringing this all together, whilst it’s tempting to view coaching as merely the application of physical and technical stimuli to your athletes in order to elicit an improvement, it is becoming so much more than this. Today, the modern coach needs to have an understanding of a broader range of skills, including, as demonstrated by this review paper, the potential ability to enhance performance by harnessing social factors and belief in their athletes as to the efficacy of a given supplement, piece of equipment, or training practice.