Fatigue during endurance exercise is a weird and complex phenomenon, and scientists are still discussing what influences it. Samuele Marcora’s group has just published an article in Frontiers in Human Neuroscience reporting two experiments studying the effect of visual cues related to happiness and motivation. They showed that such cues can make your unconscious brain think you are working out less hard than you actually are, and that therefore you will keep going for longer.
Samuele Marcora’s theory about fatigue states that the moment you stop exercising is determined by perceived effort (how hard you think you are working) and potential motivation (the maximal effort you are happy to deliver). This means that you will stop when you are judging that the effort required has become larger than the effort you want to make. This theory is called the psychobiological model of endurance performance. To delay fatigue you could therefore do two things: make the effort seem less important, or increase your motivation.
Our unconscious brain takes in much more information than we realise, especially visually. Only a tiny amount of this information makes it to our conscious attention, but we process all the information unconsciously and it therefore influences our behaviour. To study the impact of the unconscious brain on perceived effort, the researchers therefore set up a study during which they could give participants subliminal visual cues.
In their first experiment 13 participants cycled for as long as they could (i.e. to exhaustion) while looking at a computer screen. They were shown happy or sad faces on a regular basis during the effort, but the images came and went so quickly (in 16 msec) that they did not realise they were seeing them. Every participant performed the experiment twice: once with happy and once with sad faces.
In the second experiment, a well trained competitive endurance athlete cycled 12 times to exhaustion while looking at a screen showing words extremely quickly. The words were encouraging (action, go, lively, energy) during 6 workouts and discouraging (stop, toil, sleep tired) during the other workouts.
In both experiments, the participants cycled significantly longer when exposed to happy faces or encouraging words, and rated the effort as less strenuous. Their mood was not different however, proving that the information had not reached their conscious attention.
Samuele Marcora and his team concluded that these experiments confirm their theory. They also think they provide evidence against the central governor theory of Tim Noakes.
The central governor theory states that your pace, and therefore your fatigue, is determined by your unconscious brain which has to make sure that you get safely over the finish line. According to this theory your pace will thus be determined by “calculations” of your brain based on signals from your body, (e.g. working muscles, glycogen reserves), the environment (temperature, altitude…), but also on messages from your central nervous system, such as motivation, encouragement, knowledge about the course, etc…If you brain is not sure that you will get there safely, it will slow you down –or even stop you- by making you feel tired and reducing the number of muscle fibres you can use.
I am not so sure that the experiments contradict the central governor theory. Is it not likely that subliminal cues would also influence how your brain determines what you can do? Please let us know what you think!
Whatever you think about these theories, it is a good idea to surround yourself by positive images and words, and to smile to every runner you meet.
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