Believe it or not: expect to perform well to perform well!

Placebo vs. nocebo vs. nothing

While the placebo and nocebo effects have been the subject of much scientific study (albeit the nocebo less so), there is little research where both effects have been studied together (ie compared). Moreover, there’s virtually no data on how the placebo and nocebo effects compare to doing nothing (ie where an athlete believes a certain supplement or course of action is completely irrelevant to performance. But now a brand new study just published in the International Journal of Health Sciences by Brazilian scientists has investigated this question in trained men who undertook a muscular endurance performance challenge⁽⁵⁾.

What they did

In this study, 15 men experienced in resistance training were recruited (average age 41 years) and were set a task. This task consisted of performing as many bench press repetitions as possible with the resistance set at 80% of each participant’s individual 1-rep max (1RM). This task was repeated once per week over a 3-week period, and on each occasion, the men were given exactly the same supplement around one hour before the task began. This was a completely inert capsule containing 300mgs of cellulose (ie a substance having zero physiological effect). What differed between each of the three trials however was what the men were told the capsule contained and the information given to them. This was as follows:

·        Placebo - In one trial, the men were told (deceived) that they were being given caffeine. They were also given comprehensive information via an online lecture about the performance benefits of caffeine and how they could expect to improve their performances.

·        Nocebo - In another trial, the men were told (deceived) that they were being given lactic acid. They were also given comprehensive information via an online lecture about how lactic acid intake would likely harm their performances.

·        In a third trial, the men were told they were being given cellulose (ie the only trial were they were not deceived!). They were told that this would neither help not harm performance.

Fifty minutes after ingesting the capsule, the participants warmed up with two sets of fifteen (fixed) repetitions bench press at 40% 1RM with 1-minute rest periods in between. After a further 3 minutes, they performed one 80% of 1RM maximal set (until concentric failure) and at the end, they indicated on an image the level of effort performed.

What they found

The results showed that the expectations of the men (ie what they were told was in the capsule) had a very large impact on the result. Bearing in mind that all the men took inert cellulose on each and every occasion – and therefore, the number of reps achieved in each trial and perceived effort should have been broadly the same – the actual results were as follows (see figure 1 also):

·        Control (where they were told the truth – ie that they were taking inert cellulose) – 10.3 reps and perceived effort (RPE – measured on a scale of 1-10) 7.4.

·        Placebo (where they were told they were taking [helpful] caffeine) – 14.1 reps and perceived effort 6.4.

·        Nocebo (where they were told they were taking [harmful] lactic acid) – 7.5 reps and perceived effort 8.3.

The research summed up their findings (quite modestly) as follows: ‘The placebo/nocebo effects observed in this study were quite large: ingestion of placebo resulted in 37% greater performance in repetitions and a significantly lower RPE when compared to control. Ingestion of nocebo resulted in a higher RPE compared to control’. Perhaps even more remarkable is the fact that the placebo trial resulted in just under double (yes double!) the reps achieved in the nocebo trial. This suggests that expectations can play a massive role in actual performance; the performance difference that follows after telling someone they have taken a helpful supplement compared to a harmful substance is absolutely huge!

Figure 1: Average maximum reps achieved and perceived exertion (RPE) in the three trials

Implications for athletes

These results are quite startling, and demonstrate the power of the placebo (and nocebo) effect. Would they be equally applicable across all sports? This is by no means certain as the results from other studies looking at endurance performance over 30 minutes’ duration are not quite as stark⁽⁶⁾. In this study however, the researchers speculated that briefer exercise stress focused on a smaller area of muscle mass may be more subject to measurable placebo/nocebo effects.

Something else worth bearing in mind is individuality. The placebo/nocebo effect was much more evident in some subjects than others, and it may be that beliefs and expectations are more ingrained in some individuals than others, thereby modifying exercise behavior to different degrees. There is certainly some evidence supporting this theory⁽⁷⁾. In the meantime however, what can athletes do to harness the current evidence to best effect? Below are a few simple tips that may help:

·        While the evidence for some supplements is weak in clinical trials, if you honestly believe that they work for you, the chances are they will help performance. Maybe a good slice of the extra performance you experience is from the placebo effect, but so what? So long as the supplement in question is relatively inexpensive and healthy (or at least has no health risks), so what?

·        Be aware that even if a supplement you take is only delivering a placebo effect, that effect is real, and that you may perform less well if you stop taking it (even if there’s little evidence of a physiological effect!).

·        Don’t neglect the nocebo effect either. If you believe that something (a food, a supplement, your running shoes, a pre-race routine etc) is detrimental to your performance, the chances are it will be, so ignore or eliminate it. The same goes for negative thoughts and ideas that might come from others – a good reason why engaging with your rivals on the race start line might not be such a good idea!

·        Finally, while it’s great to trick the brain and try and maximize any placebo effect and minimize any nocebo effect, an even better way to guarantee enhanced performance is to use proven ergogenic supplements such as caffeine, creatine and good old carbohydrate! These kinds of supplements have been tested using controlled studies and shown to produce a significant uplift in performance, above and beyond any placebo effect thanks to the physiological benefits they deliver to the exercising body.

References

1.       Eur J Sport Sci. 2020;20:279–92

2.       Med Sci Sports Exerc. 2021 Aug 1;53(8):1766-177

3.       PLoS One. 2018 Jun 11;13(6):e0198388. doi: 10.1371/journal.pone.0198388. eCollection 2018

4.       Ann Behav Med. 2022 Oct 3;56(10):977-988

5.       Int J Health Sci (Qassim). 2023 Nov-Dec; 17(6): 39–42

6.       Sports Med Phys Fitness. 2021;61:1185–92

7.       Int J Sports Physiol Perform. 2022;17:333–4