Trent Stellingwerff: on the belief effect

November 18, 2013 7

© Copyright – 2013 – Athletics Illustrated

Dr. Trent Stellingwerff is a former track and field athlete who competed in the NCAA for division one Cornell University, where he was selected as co-captain. He also competed in the CIS for the University of Guelph, where he twice earned All-Canadian status.

Stellingwerff was an academically decorated student who made the Dean’s list at Cornell University. In 2006 he took a position in Switzerland for the Nestle Research Centre (Powerbar) as a Senior Research Scientist in Sport Nutrition, Energy and Performance. Stellingwerff has also served as the Nutrition and Physiology Consultant for Athletics Canada. He lives in Victoria, BC and is a Senior Physiologist working with the Canadian Sport Centre Pacific.

Christopher Kelsall: Would I be giving away anything should I refer to you as a pious fraud?

Trent Stellingwerff: Ha, ha – In my opinion maximizing belief effect in a sport science intervention is not fraudulent or disingenuous. Every ‘outstanding’ practitioner in sport understands that there must be some level of scientific evidence to any intervention they suggest — the science, or the evidence base, has to be there. However, outstanding practitioners also understand that placebo effect, or “belief effect” can also play a role in performance (or compliance of an intervention). In sport, the connection you have with the athlete/coach, and “how” you talk about interventions is as important as “what” the intervention is (or science behind the intervention).

As a scientist I try to eliminate all bias by running double-blinded, placebo controlled, cross-over trials – where both the subject and the scientist are blinded to the intervention. This is really the “gold standard” of the scientific approach.

However, as an applied sport practitioner I am not concerned about bias – I want to leverage all the bias I can get into “belief”.  And that belief is included in myself and belief by the athlete and coach. To me this is not fraudulent.  If I have done my homework (e.g. studied for 20-plus years, looked at all the research papers, reached out to my international network for insider information, done some internal research and trial/error) and I truly believe in an intervention, I want the athlete/coaches I work with to know that I am convinced this will help them, that I have done my homework, and that they are in good hands with me – that they have a strategic advantage by applying new knowledge into a new intervention. In this situation, we have both evidence and belief maximized – which is perfect in the applied sport sciences as both have been shown to improve performance separately.

Long story short, I personally always need some evidence for an intervention – anyone is welcome to challenge me on my evidence base on any intervention I suggest. Conversely, a practitioner with limited to no evidence, but outstanding “belief effect”, is a snake oil salesman and I would suggest staying far away from these types.

CK: In search of the next advancement in athletic training, would you suggest the mind is the next frontier?

TS: Partially yes. Instead I would say that combinations of sport science disciplines are where the next breakthroughs are most likely to come. We are in an interesting paradox – to become an expert in any field you have to absolutely dedicate and focus yourself to that field, or sub-discipline within that field. However, I would suggest that a lot of the new sport science breakthroughs are going to come through cross-disciplinary approaches. For example, some of the most interesting research data I have read in the last few years have come from studies combining a psychological and physiological study designs, examining how the brain and body interact to optimize performance. In many ways, the applied sports practitioner has to become an “expert generalist” being able to link and apply many interventions across many scientific disciplines to optimize performance.

CK: It is interesting that today there continues to be little (albeit growing I am sure) expert usage of psychology in athletics training by the coaches, but the work on the subject started at least in the 1500s with Ambroise Paire.

TS: Indeed, I think a lot of this has to do with what we can measure. It is much easier to quantify things from the neck down (physiology/biomechanics) – e.g. VO2max, blood lactate, force, power output and correlate these quantitative data to performance outcomes. It is much more difficult to measure things consistently from the neck up (psychology), as it is much more individual and qualitative in nature. However, I would suggest athlete psyche and mental aptitude is a huge player in overall performance outcomes – especially at the elite level.

It would be an interesting theoretical study at the Olympics to screen and measure physiological and biomechanical metrics of all Olympic finalists – then blind the data set, and I am pretty certain it would be very difficult for experts to try and pick winners based on the data. Conversely, at pre-Olympic training camps you can almost sense the athletes who are psychologically coming into their own  (gaining confidence), who are getting ready to perform optimally on demand – this really captures the complex nature and “art” of coaching, and the delicate balance that the applied sport practitioner plays.

I would also highlight, at least with most of our Olympic targeted teams and athletes, sport psychology is an important aspect and part of the modern integrated support team.

CK: Kenenisa Bekele got beat in the London Olympic 10,000m final by Mo Farah. This year, Bekele said before the Great North Run, that when in shape, he is faster than Farah. Bekele indeed won in 60:09, finishing with a kick, which ironically Farah is also known for. He must have known something, yes? Was the difference simply about confidence?

TS: This is an almost impossible question to answer, as there are so, so many things at play in assessing performance. Fitness and belief (confidence) are only two elements out of probably 100-plus.

However, I also look at performance statistics. There is a whole area of sport science based on the statistics of performance, which has a lot to do with normal variability of performance (coefficient of variation; % CV).  As an example, if I took a well-trained 1500m runner and made them time trial a 1500m once per week for four or five weeks straight under the exact same conditions what would the normal/natural variability be?  Long story short – most elite athletes show about 0.5 to 1% variability in their performances at their peak. (so over a four minute 1500m that is about +/- 2.5 seconds).

Coming back to the Great North Run, there was one second between Bekele and Farah, which works out to a performance difference of just 0.028% — well within the 0.5 to 1%.  So, I would suggest that statistically, if they just re-ran the race you would be just as likely to have Farah win as Bekele. Now, if Bekele had beaten Farah by more than 0.5 to 1% (~18 to 36 seconds), than on re-running the race Bekele would be statistically much more likely.

CK: Of course an unanswered question (I assume one of the 100-plus items) is how maximal was Bekele going? He just needed the win, right! Based on his pre-race confidence, I would suggest it was not a 100% effort. Bekele’s bests at shorter distances point to a 58-high/59-low half-marathon. Comparitively there is approximately a 1.2 % difference in their 5000 and 10000m personal bests: 12:53.11 and 26:46.57 versus 12:37.35 and 26:17.53.

TS: Bingo – spot on! The only athlete that doesn’t have to go full out (in theory) is the winner.

CK: Is there good advancements for the neck up portion of training happening at this time? It seems coaches typically continue to bring in sports psychologists, just as they do physiotherapists and other professionals to complement the coaching package.

TS: I’m sort of getting out of my area of expertise here. But, from what I have observed from great sport psychs, they absolutely engage the coach in their process, involve the entire team dynamics, as well as one-on-one consultations – so yes, our elite Olympic level coaches are getting feedback and training in areas of psychology (if they request and want sport psychology as part of their “team”). Some sport psychs also work with members of the integrated support team (sport science and medical), to see how we interact with the coaches/athletes. In my opinion, the “biggest” influencer of an athlete’s psyche is who is around them the most – and that may be their partner, roommates, coach, teammates, family/friends etc. So, some element of sub-conscience “psychology” happens every day with the way athletes interact with their coach, their teammates and their support teams.

CK: You have shared a study about CHO (carbohydrate) mouth wash. Is this to fool the mind/body into believing that carbohydrates are on the way – is it an effective way to practice training low and racing high?

TS: Indeed, as I mentioned above one of the areas that is absolutely intriguing to me is this physiology/psychology interaction, and there are seven-plus studies that have now shown that just washing your mouth out with CHO (5 to 10 second rinse of a 25ml 6% CHO solution = normal sports drink concentration) every 10 minutes in a 30 to 60 minute time trial will improve performance compared to an artificial sweetener mouth rinse. You have read that correct: Just swilling sports drink in your mouth and spitting it out and consuming nothing, compared to swilling artificial sweetener, can improve 30 to 60 minute time trial performance by 2 to 3%! (Note: you can consume the CHO beverage too, and you should in longer races, but the mechanism appears to be that taste sensors in the mouth directly signal the brain, so the key is to have the CHO in the mouth for 5 to 10 seconds before either spitting out or swallowing).

At first, I did not believe this data. But there are now fMRI brain imaging studies showing that just washing your mouth (swilling) CHO for 5 to 10 seconds actually lights up the pleasure and reward centres in the brain. This “positive” cognitive reinforcement drives the body to push more wattage, lowers ratings of perceived exertion (RPE), and allows athletes to perform better.

I co-supervise a PhD student at the University of Victoria (Matt Jensen), who just did a CHO mouthwash study and looked at force outputs via Biodex leg extension machine after a 5 second CHO mouth-rinse versus a placebo condition. We found an instantaneous effect when athletes were slightly fatigued, which suggests it might even be advantageous in explosive workouts when fatigued to do a CHO mouthwash every 5 to 10 minutes. We also used EMG (electromyography) and also showed an immediate effect after CHO mouth rinse in that the muscle fibers appeared less fatigued – which relates back to the central nervous system and the brain, and then allows the muscle to create more force. We are just writing this paper up for publication now, so hopefully it will be out soon.

CK: You say it provides an instantaneous effect when athletes were slightly fatigued, does the effect last as long as it would with full digestion of sports drink?

Good question. First off, the CHO mouthwash effect has only been examined in performance studies from 30 to 60 minutes in duration where they mouth-rinse for 5 to 10 seconds every 10 minutes of the time trial (cycling or running). In other words, muscle glycogen in not limiting. When performance is required over 60 to 90 minutes, or longer, than consuming (not mouth rinsing) sports drinks also provides fuel to the working muscles. So there is a complex interaction between CHO providing a cognitive boost via taste receptors in the mouth, and then a fuel that can be used during prolonged exercise.

Since there have been no studies done lasting longer than 60 minutes with CHO mouthwash, I cannot answer your question on how long the effect lasts. However, just yesterday, I was at a final study design planning meeting with the same PhD student where we discussed a study attempting to answer this question (effect of CHO mouth rinsing after two hours of exercise).  So, I can probably answer this question for you in about six to eight months once we get all our subjects done in the study and we have crunched all the data.

CK: Can you provide a specific example of this interesting research data you are referring to, earlier?

When it comes to performance involving fatigue, an athlete’s personal ratings of perceived exertion (RPE) are intimately linked to pace judgement. Now, I think some folks get very focused on whether RPE is central governor mediated (neck up) or peripheral (neck down) dependant (efferent or afferent). I’m in the middle – why can’t it be both, via a complex interplay of peripheral fatigue and central perception of that fatigue and the memory of experience? So, both efferent and afferent feedback to dictate an athlete’s current RPE, and other data (split time, wattage, HR if available) and whether they can push harder and go faster.

So that said, over the last few years, there have been a host of studies showing that an athlete’s perception (or change of RPE) can be adaptable. For coaches, this is not at all surprising – as they would just call this “mental callusing”.  For example, just swishing your mouth out with CHO lights up the pleasure and reward centres of the brain and makes an athlete “feel better” (lowers RPE) so they can push harder (for review see:  Another mouthwash study, done in the heat, used a menthol mouthwash – so it gave the perception of cooling, which also increased performance in the heat compared to a water only mouthwash ( A study just out last month showed that an athlete who can engage in positive self-talk can improve performance (see: This same research group (Dr. Samuel Marcora), is also working on brain training to improve physical performance (read a great blog on this here: ).  Finally, a few years ago an interesting study not only found a placebo effect of caffeine (giving subjects nothing, but telling them they got caffeine to improve their performance), but a dose-response placebo effect:  There are a whole host of other recent papers as well.

Now, do these effects work as great in the truly elite and athletes who already have been through physiologically, and more importantly, psychologically taxing training? That remains to be examined.

So, going back to one of my first answers:  If I am personally convinced of an intervention, and I can provide the evidence for an athlete/coach to also be convinced (high belief effect) and the intervention actually has a physiological mechanism/benefit, than we have the best of both worlds: a maximized physiological performance benefit coupled with maximal belief and confidence in the intervention.

To give a practical recommendation coming out of this interview, I would suggest that athletes, coaches and support staff have a clear understanding of what makes the athlete and coach tick. Does the athlete and/or coach want to know the “why” behind the training or intervention? Or are they just happy to trust their coach and support staff?  What do you as an athlete need to know that you are getting 100% of the best level of training and sport-science support? What questions do you need to ask?  Finally, the power of positivity can never be under-estimated. Try and find ways to be positive and try and surround yourself with like-minded individuals.





  1. George Beinhorn November 29, 2013 at 1:08 am - Reply

    Does washing the mouth with CHO signal the brain that it’s okay to release carbs from storage because more CHO is on its way? If so, this might be a “scientifically verified strategy” that proves dangerous if carried too far, since the body in its wisdom reserves carbs to protect the brain and heart, its two most carb-dependent organs.

  2. Micky November 19, 2013 at 4:39 am - Reply

    I wonder what is his view on altitude training – whether it is placebo based or scientific. This site suggests the former:-

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