Who Sets Your Running Pace – You or your CNS?


By Rick Morris


I came around a blind corner and entered the finishing area of the marathon I was competing in. I found myself looking at a large parking lot that had a confusing pattern of chutes that were funneling the runners through the final stage of the race. Feeling a bit like a mouse in a maze I entered the finishing area and was met by a group of spectators cheering me on – telling me I had about ¼ mile to the finish line. I had run a good race and felt strong – or as strong as you can feel after 26 miles. I picked up my pace a bit so I would look good for the photo op at the finish line. After about ½ mile I realized that the spectators telling me I had ¼ mile left were sorely mistaken. In reality I had nearly 1 mile left. I suddenly began to feel very fatigued. The last ½ mile of the race were the most difficult I ever remember running.


I had a very similar but opposing experience in a recent 10K race. The event featured both a 5K and a 10K race. Both races started at the same time. The 10K race was two loops of the 5K course. I was running the 10K and as I approached the end of the first loop I saw a sign that said 10K finish pointing to the right. Thinking that was the 10K course I made a right turn and kept going. After I had gone about ¼ mile I heard a volunteer yelling at me, telling me that the 10K course continued on the left hand route for another loop. I was in the lead at the time, so after kicking myself in the behind for my stupidity, I took off on the correct route for another 5K. At that point, I was thinking only of trying to regain my lost ground during the final 5K of the race. I forgot about the first half of the race and focused on the last 5K.  I ran hard and was able to not only regain the lost ground but ended up running my fastest 5K of the year over the final 3.1 miles of that 10K race!




























Why did the final ½ mile of the marathon seem so hard? The final miles of a marathon are always difficult due to glycogen depletion and muscle fatigue. By it was almost like a switch was flipped. I felt pretty good up until I discovered I had longer to run than I realized. In the same vein, why was I able to run such a fast 5K in the last half of a 10K race? Physiologically, I shouldn’t have been able to do that.


Researchers in South Africa believe that the answer may l lie with another question. Who is setting your pace – you or your central nervous system (CNS)? That may seem like a silly question. After all, you consciously set you own running pace, don’t you? Of course you do, at least in part. But the researchers have found evidence that your CNS may play a sub conscious role in setting your running pace.


The researches solicited the help of sixteen moderately trained distance runners. Each of the subjects participated in three treadmill running trials at 75% of their peak running speed. In the first trial the subjects were told they would run for 20 minutes, which they completed. In a second trial they were told they would run for 10 minutes, but 9 minute into their run they were asked to run for another 10 minutes for a total of 20 minutes. In the third trial they were not informed of how long they would run, but were stopped after 20 minutes.  The results were very interesting.


The participants reported a much higher rating of perceived exertion (RPE) at 11 minutes in the second trial when they were deceived about the running time, when compared to the first trial when they were honestly informed they would be running for 20 minutes. Exercise intensity, oxygen uptake, heart rate and stride frequency were unchanged. So there was no physiological basis for the increased RPE in the second trial. According to the researchers, this suggests that a runner will display “symptoms” or more appropriately “feelings of fatigue” that match their expectations or anticipation of what is to come.


Another interesting finding emerged from this study. During the third trial, when the subject had no idea of how long they were going to run, oxygen uptake levels were lower, even though the running speed and intensity were the same. The only reasonable explanation for that is an increase in running economy. It is thought that when the runners were unsure of the exercise duration they subconsciously more economical in order to maintain a reserve in anticipation of longer duration.


The results of this study support the recent central governor theory of fatigue in which it is thought that your CNS will anticipate the energy requirements of your run and will “dole” out energy and muscle motor unit activation to insure that your body maintains a balance or homeostasis for the duration of your run. It’s believed that your CNS actually calculates the energy costs of your upcoming run and sets your pace accordingly.


How does this rather controversial theory play out in real life? I think it does very well. It explains my own personal experiences outlined above to perfection. In the marathon example I expected to be finished in ¼ mile. My CNS responded with a burst of strength and energy. Once I discovered that I had nearly a mile to go, my RPE went through the roof.


In the second 10K example, my CNS had set my pace to my usual 10K pace for the first half of the race. After I made a wrong turn my focused changed from running a 10K to completing a 5K and regaining lost ground. I forgot about the 10K. My CNS “reset” to a 5K distance and I was able to run that second half of a 10K at a blistering 5K pace, while maintaining a moderate RPE.


This is a controversial subject that will have both believers and those that think it’s hocus pocus nonsense. I personally have become convinced in the accuracy of both the central governor theory of fatigue and the even newer theory that your CNS plays a role in not only pace selection, but feelings of fatigue. It’s your choice whether to jump on the CNS bandwagon or not. For me these new theories open up a whole new frontier in both the physiology and psychology of running. It’s giving me new ways to improve my running performance and my enjoyment of running. I don’t see a downside. On the other hand I could just keep doing what I have been doing and keep getting what I’ve been getting. Is that really a choice?




Effect of anticipation during unknown or unexpected exercise duration on rating of perceived exertion, affect, and physiological function. DA Baden, TL McLean, R Tucker, TD Noakes, A St. Clair Gibson, Br J Sports Med 2005;39:742-746


Evidence for complex system integration and dynamic neural regulation of skeletal muscle recruitment during exercise in humans, A St Clair Gibson, TD Noakes, Br J Sports Med 2004;38:797-806





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