Which Comes First, Cardio or Weights_ - Alex Hutchinson [93]
If my brain is tired, will my body’s performance suffer?
Many people spend their workdays sitting on a chair in front of a computer, with physical exertion limited to an occasional stroll down the hallway. From a purely physical perspective, it’s hard to imagine a cushier existence. But if you head to the gym after work, you might notice that your performance suffers when you’ve spent the afternoon wrestling with a particularly complicated problem. In 2009, researchers from Bangor University in Wales published the first rigorous investigation of this phenomenon in the Journal of Applied Physiology. They asked 16 volunteers to ride a stationary bicycle to exhaustion under two different conditions: once after taking a challenging 90-minute cognitive test and once after passively watching 90 minutes of documentaries about trains and cars. Sure enough, the subjects who had been using their brains reached exhaustion after 10 minutes and 40 seconds on average—a full minute and 54 seconds before the movie-watchers.
It’s possible that thinking actually burns up enough energy to affect your physical performance: the test-takers recorded slightly higher heart rates (65 beats per minute) compared with the movie watchers (62 beats per minute), likely due to the brain’s heightened demand for glucose. But the data taken during the cycling test suggest that this wasn’t a significant factor. The two groups produced identical physiological responses to exercise, as measured by quantities such as heart rate, oxygen consumption, and blood lactate. The only difference was in their subjective rating of how hard the exercise felt: right from the moment they started pedaling, the mental-fatigue group rated their perceived exertion a few points higher on a scale of 6 to 20. Both groups stopped pedaling when their perceived exertion hit 20—which means the mental-fatigue group stopped earlier, with lower physiological measures of fatigue than the control group.
For the researchers, this finding offers powerful evidence that our traditional understanding of exhaustion as the result of reaching some physical limit in the body’s capabilities is flawed. “Overall, it seems that exercise performance is ultimately limited by perception of effort rather than cardiorespiratory and musculoenergetic factors,” they wrote. Intriguingly, our perception of effort during exercise is regulated in a part of the brain called the anterior cingulate cortex—which is precisely the part of the brain activated by the 90-minute cognitive test used in the experiment. This suggests that a bout of hard thinking might disrupt our sensation of physical effort, even though the muscles themselves are completely unaffected. The most eyebrow-raising implication of this study is that it might be possible to improve physical performance through brain training, without leaving your armchair, by postponing fatigue of the anterior cingulate cortex. The Bangor research team is in the process of testing this remarkable hypothesis.
For elite athletes, the study highlights the benefits of a period of mental relaxation before particularly hard workouts or competitions. In general, though, the researchers are careful to point out that exercising after work is still a great idea: the effects of mental fatigue will have only a minor effect on moderate exercise, and the workout is a great source of stress relief. Still, it’s worth bearing in mind that if you’ve been pulling an Einstein at work, you might need to cut yourself some slack at the gym.
Does it matter what I’m thinking about when I train?
For many people, heading out for a run or a bike ride offers a mental break—a chance to think about the events of the day, or about nothing at all, while the legs navigate on autopilot.