Here is the abstract:
Although placebos have repeatedly been shown to increase physical performance and endurance, much less is known about the effect of their negative counterpart, nocebos. Here, we employ negative suggestions and a sham electrical stimulation as a nocebo conditioning procedure in healthy subjects performing a leg extension exercise to total exhaustion. Using two different protocols, we analyze the contribution of expectation alone or the combination of conditioning and expectation to the nocebo effect evaluated as the change of work performed and rate of perceived exertion. We find that it is possible to negatively modulate the physical performance in both cases, and we argue that this effect can effectively offset the outcome of training programs.
The discussion in the paper is instructive:
The main finding of this study is that it is possible to negatively modulate the performance of subjects carrying out a muscle exercise to volitional maximum effort by employing discouraging suggestions and negative conditioning.
I do find this study absolutely fascinating. The whole idea of the power of belief in health and healing is realitively well known - we have all heard of the placebo. But what is less well known is the nocebo - the idea that rather than positive benefits, there can be negative impacts from certain contexts and expectations: you can get worse.
What is interesting here is how nocebo effects extend to exercise performance - hearing negative suggestions can impact how well you perform.
All this stuff about the impact of the mind is so important and could potentially trump all other effects - diet, exercise whatever. If you think it is doing you good it will. If you think it is harmful, then it will be. It is like Samuele Marcora's work on the psychobiological model of fatigue - the impact of perception is so important.
By the way, coincidentally, Chris Kresser had a great podcast on this this week with a full transcript here: The Placebo Effect and The Power of Belief in Healing
In some ways this is all like epigenetics - the impact of environment, in this case perceptions and expectations, outweigh what seem to be the bigger more obvious factors.
The search for the perfect diet or exercise routine may be pointless.....the most important element to either is what you believe about the diet or training regime.
Dr Kurt Harris has a good post on placebo here.