Keeping Things the Same Requires Making Changes

Our brains are inside our bodies and rely on sensation and feedback to understand the reality of the external world. How does your brain know how to adapt its attempts to regulate your body movement in the face of changing conditions related to getting tired or getting older?

Muscles are Wise

When I was an undergrad, I learned something in an exercise physiology course that absolutely blew my mind. My professor was discussing the physiology of fatigue and how we are able to keep performing for long periods of time even though our muscles are getting tired. That was the day I learned about "muscle wisdom."

Brenda Bigland-Ritchie was a phenomenal and pioneering scientist who was interested in how the motor neurons in the spinal cord communicated commands to the fibres in the muscles of the limbs, particularly in how this might change with fatigue. To assess this back in 1983, she and her colleagues at Quinnipiac College (now University) in Connecticut measured the properties (speed of contraction and relaxation) of muscle along with the commands (discharge rates) of the neurons controlling the contractions.

They noticed something kind of peculiar--during a sustained series of contractions, when fatigue was building up, the discharge rates dropped much more than did muscle force. Usually, there's a very close correspondence between these two. When they measured what the muscles were doing, they found that there was a slowing of relaxation for the fibres. In order to continue to get the most out of the muscle, the nervous system needed to reduce the demand instead of increase it. This allows our muscles to do their physiological finest.

This somewhat counterintuitive idea became known as the "muscle wisdom wisdom" hypothesis. It has lived rent-free in my brain since I first learned it in 1988. It's in my head as an example of how the nervous system adapts itself to the changing conditions of the motor system in order to allow peak performance for as long as possible despite our sense of effort. Or maybe even for as old as possible?

Slow to Peak

Very recently, Erik M Summerside, Robert J Courter, Reza Shadmehr, and Alaa A. Ahmed from the University of Colorado and Johns Hopkins University wanted to understand why "we move slower as we grow older." These scientists noted that connections in the brain that reinforce and reward actions decline as we age. Perhaps we don't value the same movement characteristics with aging? Or, maybe it's because we have to make more and more effort to move quickly?

In a clever series of experiments, they studied reaching tasks in younger ( about 25-year-old) and older (about 75-year-old) adults and found that "older adults consumed more energy than the young at a given speed." They then studied the effect of reward on movements. Older folks, as with the younger ones, started movement earlier. Unlike younger folks, though, older adults did not move quicker and "they were unwilling to increase their movement speed."

Erik Summerside and colleagues then made movement harder for the younger folks in order to mimic aging and found that they now behaved like the older participants. This suggests that "slower movements in older adults are partly driven by an adaptive response to an elevated effort landscape" and that slower movement "may be a rational economic response the brain is making to mitigate the elevated effort costs that accompany aging."

Your Brain and Body Know That Less Can Be More

The takeaway here is that as we do things, either in the moment where fatigue might develop or over time as our bodies change with aging, there is a constant adaptation of brain and body to allow for optimal outcomes. From a martial arts perspective, this is quite consistent with the popularity of slower training with aging. This is also consistent with the observation that many martial artists who begin in more high-energy "athletic" systems like Korean Tae Kwon Do and Japanese Karate tend to migrate towards traditions like Chinese Tai Chi Chuan as they reach more seasoned decades of training.

The bottom line is that we can continue to produce effective movement and high-quality physiological function across the lifespan. We just have to alter how we do things to match the current conditions. Like Giuseppe Tomasi di Lampedusa wrote in The Leopard, “If we want things to stay as they are, things will have to change.” Your aging brain knows how to match the function of the other bits of your body. So let them do their job, especially when less means more.