Dr. Daniel Lieberman, professor of evolutionary biology at Harvard University, published “Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding” on January 5th, 2021.
I previously read Lieberman’s book “The Story of the Human Body” published in 2015. This book provided much of the foundation for my understanding how and why modern homo sapiens evolved for movement. Early books review indicated thatExercised appears less technical and easier to read than The Story of the Human Body.
When a colleague of mine shared a New York Times article featuring this Lieberman’s new book, I couldn’t wait to read or listen to Lieberman’s take on exercise. After all, as a behavior analyst, I’m intrigued any time an article or book title includes the term “rewarding”…this usually implies there will be some analysis of consequences.
Lieberman joined Michael Shermer on his podcast The Michael Shermer Show to review this new book.
Here’s my take on that interview:
What I Liked
”That’s beyond my expertise…”
Countless times, Shermer asked questions outside of Lieberman’s expertise. Like a true scientist, Lieberman responded by saying that the subject matter (e.g., sleep, nutrition) extended beyond his scope, but offered his educated opinion.
Foundational Concepts Addressed
For anyone new to physical activity, or wants to understand general concepts regarding this subject matter, this interview provided a nice overview and did not get too into the weeds. Shermer asked interesting questions that most people would ask (e.g., “What’s the science behind Body Mass Index?).
The term “Exercist” and Fitness Shaming
Lieberman invented the term “exercist” to identify fitness nuts, enthusiasts, and folks that are all about health and fitness. They are on a crusade to get everyone exercising all the time.
We know those people. I may be one of them…
Lieberman stated that the trouble with some exercists (but not all) make other people feel bad about NOT working out. “Oh, you don’t workout?!?!, No gym membership, then shame on you!” We shouldn’t make people feel bad because they do not engage in certain exercise and fitness behaviors.
People may be starting from scratch, recovering from an injury, or going through a hard time. There are many barriers to exercise for people that do want to exercise. Any form of fitness shaming can discourage and even punish the slightest effort towards a healthier lifestyle.
I can stand behind no fitness shaming.
and related…
”Exercise is Medicine”
Lieberman described that the pitfalls of treating exercise as the antidote to everything oversimplifies the multiple, multivariate systems that compose our human body. Multiple, multicellular organs harmonize our bodily systems (e.g., respiratory, circulatory, digestive) 24 hours per day. Exercise, sleep, nutrition, and stress each affect these systems, to different degrees, at different times of day.
Exercise is but one lever to improve health outcomes whatever the measure. One of thousands of inputs that affect our entire system. Yes, the research is clear that exercise provides tremendous benefits, but it is one cog on our path to create a happy and healthy life. Whatever that looks like.
What Dr. Lieberman missed
Lazy By Selection
From his perspective, Lieberman explained everything in terms of selective advantages or reproductive fitness. Those most “fit” survived and passed on their genes. Evolution 101.
If it is not advantageous for us to be active all day, then hunter gatherer will relax and have a lot of down time. No exercise needed. We conserve our energy.
However, fast forward to today, Lieberman’s explanation of “why don’t people exercise today?”, is a classic evolutionary mentalistic interpretation: it’s in our genes. We are lazy and inactive because selection made this way. To a point.
Enter Contingencies
The contingencies for survival were simple 100,000 years ago. Move, find food, drink water, survive, and reproduce. The contingencies are still simple, but today, survival requires little physical activity.
Here’s the behavioral piece that Lieberman missed: there are functional reasons as to why people are inactive today.
Yes, our genetics may predispose to us accumulating fat during energy scarcity and walking efficiently, but when our basic biological needs are met, then considering how the current environment affects our behavior plays a role.
The environment produces consequences, either reinforcers or punishers, that increase or decrease the odds that we will engage in a given behavior. These are the functional pieces. For example, I can gain access to a dinner by either hunting a deer, butchering the carcass, and grilling it over a campfire. Or, I can order farm fresh venison shipped to my front door. Both behaviors produce the same outcome, deer for dinner. Same ends, different means.
Hunting behaviors in the first example, website searching and ordering online in the second. Neither behavior is inherently good or bad, they just happened. Just like evolution, it just happened. Selection by consequences happens everyday.
Lieberman seems so close to including selection by consequences into his work. After all, he is world-renowned expert in natural selectionand teaches at Harvard, where famous behavior analyst B.F. Skinner applied selection by consequences in his lab. Beyond the deer dinner example, evolutionary pressures (e.g., heat, access to a mate) drive the behaviors that are selected by the environment.
Romanticizing How Athletes Accomplished Extraordinary Feats
Lieberman was often enamored by how Shermer could “all of a sudden” bike across the United States, or how his graduate student could not carry a watering can on his head like native African tribeswomen.
Enter a simple behavior principle: Shaping.
Michael Shermer did not one day go from 0 to 1000’s of miles overnight. I’m sure that he steadily increased his training time and volume over years. The tribeswomen likely learned this skill early in childhood, gradually increasing the size of watering cans and the total weight (up to 20% of bodyweight!). The graduate student did not put in the same repetitions.
What lead Shermer to biking across the United States? Reinforcement. Shermer described how he enjoyed the breeze (an automatic reinforcer), being outside and sharing time with riding buddies (a social reinforcer). What lead tribeswoman to march across the savannah with watering cans? Reinforcement. The tribeswoman contacted reinforcement by gaining access to water (an automatic reinforcer), providing water to her family, and sharing social time during her walks (a social reinforcer).
After each behavior became more efficient – Shermer’s cardio engine and the tribeswomen’s balance – larger gains were possible. Shaping, or small successive improvements over time,selected which behavior survived to produce remarkable outcomes.
The behaviors evolved. Ironic, huh?
All Recommendations Related to Longevity
Finally, Lieberman missed his own advice on this one. His arguments were simplified in terms of longevity. Most research and health recommendations – no matter where they come from – are positioned in terms of how long people live. A quantity of life versus quality of life argument. That’s ok.
Move more, exercise more. These behaviors will improve your odds of living a better life down the road. You will be less likely to develop diseases that require time to develop heart disease, diabetes, and various cancers.
By focusing on these simplified long-term health risks, Lieberman neglects that other short- to medium-term health consequences happen. Enter all things stretching, ergonomics, flexibility, and back pain.
To bolster his take on not oversimplifying health, he railed against the concept of “sitting is the new smoking,” citing that hunter gatherers sat many hours per day.
(they also didn’t have chairs and have perfect squat form, which is another blog on its own).
By only focusing on long-term health outcomes, Lieberman failed to mention short-term health effects related to physical inactivity or excessive desk sitting like restricted blood flow, tightened muscles, back, neck, and shoulder pain.
Sit in a chair all day in a C-shape position and tell me that you will not experience short-term pain, or be a candidate for a slipped disk! Won’t happen. Back pain, or problems developed from excessive sitting may not directly impact longevity (as measured by standard heart health studies), but will contribute indirectly by limiting yourself to be an active human. It’s hard to move effectively and efficiently when you spend the majority of your day in poor positions. People with bad backs don’t get around too well…
Longevity may be important to you, but a lot happens between birth to death. Designing our ideal life requires us to consider more than variables associated with long-term health risks.
(image credit: Skeptic.com)
