"Now if you are going to win any battle you have to do one thing. You have to make the mind run the body. Never let the body tell the mind what to do. The body will always give up. It is always tired in the morning, noon, and night. But the body is never tired if the mind is not tired.”

- George S. Patton, U.S. Army General, 1912 Olympian

Friday, April 9, 2010

Giving Up: Neuromuscular Safety Mechanisms (Part 1)

Another intriguing research study and interview hit my inbox a few weeks ago. This one comes from researchers Samuele Marcora and Walter Staiano of Wales’s Bangor University. You can find the full text of the article on the Journal of Applied Physiology’s website (it’ll cost you $8 to read it…or you can wait until it’s free). It’s a surprisingly simple study. Don’t let that fool you though. The results, consequent discussion and possible applications are potentially breakthrough in nature (though the researchers have met opposition from colleagues and more research needs to be done). In a nutshell, here’s the experiment:

10 male athletes were asked to pedal on a cycle ergometer as hard as possible for 5 seconds and power output was recorded (maximal voluntary cycling power, or MVCP)

They then rode same bike as long as possible at a fixed power output level, set at 90% of their individual VO2max (VO2max is basically the maximum capacity of an individual’s body to transport and utilize oxygen during exercise).

When they could no longer pedal at a pace required to maintain the fixed power output level, they were deemed “exhausted (the average time was approximately 12 minutes).” Immediately upon reaching the point of exhaustion, they repeated the 5-second MVCP test.

Pretty simple idea, yes? Here’s what Drs. Marcora and Staiano found:

First, 30% less power was produced in second MVCP test (in an exhausted state) than the first (in a fresh state). No big surprises here.

Second, power output in second MVCP test was approximately 3x greater (731 watts) than the power that was required to be maintained in the ride to exhaustion (242 watts).


To restate: They rode themselves to exhaustion trying to maintain 242 watts of power output. And then produced 731 watts of power in a 5-second MVCP test. What does this mean? To quote the researchers in the European Journal of Applied Physiology:

“It is traditionally assumed that exhaustion during high-intensity aerobic exercise occurs because fatigued subjects are no longer able to generate the power output required by the task despite their maximal voluntary effort…We have demonstrated for the first time that this is not the case… [I]f our subjects were able to voluntarily produce 731W for 5s immediately after exhaustion, they must have been physiologically able to produce 242W for much longer. The most likely explanation for the very high MVCP produced immediately after exhaustion is psychological. Subjects knew that the final MVCP test was going to last only 5s, and such knowledge motivated them to exert further effort after the time to exhaustion test which had a longer and unknown duration.” (emphasis added)

What does this mean? Could the true cause of endurance fatigue really be just a perception of effort?

Matt Fitzgerald, a senior editor at Competitor Group recently conducted an interview with Dr. Marcora, the full text of which can be found on the Competitor Running website.

As Dr. Marcora explains:

“My proposal is actually based on general motivation theory. What we call exhaustion is not the inability to continue; it’s basically giving up. The reality is that the neuromuscular system is actually able to continue. My idea is that it’s basically a safety mechanism like many other sensations. So you have sensations motivating you to take a certain course of action for survival. Think about thirst or hunger or pain. All these sensations are there to make us do something. That is actually beneficial for our survival, and I think perception of effort does the same.”

If fatigue is nothing more than a perception of effort or a neuromuscular safety mechanism designed to protect us from ourselves, can it be overridden? Can it be desensitized, in a sense, or be trained to trigger only at more intense stress levels? Can we train and/or convince our body’s safety mechanisms that we know what we’re doing? That we know what we’re asking of ourselves physically? That everything is alright and no brakes need to be applied just yet?

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