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February 21 - February 26, 2021
Isometric muscle actions can be challenging, but it is even harder to lower the weight very slowly by extending your elbow. This sort of eccentric muscle action requires your biceps to fire as it lengthens.
Among other things, these genes augment the total number and thickness of muscle fibers, thus expanding the muscle’s diameter, making the muscle stronger.42
If you primarily want to gain strength, you’ll get the most bang for your buck by slowly doing a few demanding repetitions of weights that require eccentric or isometric contractions.44
That said, if you are more interested in power and endurance, you’ll derive more benefit from multiple sets of fifteen to twenty rapid concentric repetitions on less demanding weights with only brief rests between sets.45
As a mere mortal who needs to work for a living, avoids gyms, and prefers cardio over weights, I’d like to know how much resistance training is enough to accomplish my goals.
Every form of martial arts emphasizes balance, posture, developing protective reflexes, and generating force effectively with proper technique.
crucial characteristic revealed by an evolutionary anthropological perspective: the control of reactive aggression.
Although far from easy, dieting is unquestionably more effective for shedding many pounds.
Finally, it truly is faster and it’s often easier to lose weight by dieting because everyone needs to eat but no one has to exercise, and not eating five hundred calories of energy-rich food (four slices of bacon) requires less time and effort than walking five miles a day.
If the nuchal ligament was an adaptation to stabilize the head during running, here was evidence that millions of years ago humans had been selected to run.
Note that humans can run long distances above the trot speed of dogs, ponies, and sometimes even horses.
What enables ordinary humans who descended from flat-footed apes to be so good at endurance running?
Most obvious are our long, springy legs.
For a given endurance speed, good human runners have lower stride rates and similar stride lengths to a full-sized horse.
Beyond our high-performance legs, the most vital and unique adaptation that enables humans to go the extra mile is our ability to perspire profusely.
Speed versus stride length (top) and stride rate (bottom) for a good human runner, greyhounds, and horses. E, endurance range; S, sprint range; T, trot; G, gallop.
Sweating effectively turns the entire body into a giant, wet tongue.
Meat is a nutritious food, but given the risk of being kicked or gored while getting up close and personal with an angry wildebeest, it’s remarkable that more of our hunter-gatherer ancestors weren’t vegetarian.
Good running form (on right) compared with common poor form (left).
All in all, the modest physiological stresses caused by exercise trigger a reparative response yielding a general benefit, a phenomenon sometimes known as hormesis.47
with the exception of intermittent fasting, none is yet supported by solid evidence as a way to extend human longevity.54
How physical activity affects health span (morbidity) more than life span (mortality). Typical health span and life span in hunter-gatherers (top) compared with industrialized people (bottom) who are physically active or inactive.
The Stanford Runners Study. This study measured the probability of surviving in a given year (top) and disability (bottom) over two decades in a group of amateur runners over fifty in 1984 compared with a group of healthy but sedentary controls. After more than twenty years the runners had 20 percent higher survival rates and 50 percent less disability.
the best advice for staying healthy as we age hasn’t changed in centuries: don’t smoke, avoid obesity, eat and drink sensibly, and of course stay physically active.
For most of us, however, the problem is not recognizing the benefits of physical activity but overcoming natural disinclinations to exercise at any age and figuring out how much and what kind of exercise to do.
The routine brought to mind the running guru George Sheehan’s observation that “exercise is done against one’s wishes and maintained only because the alternative is worse.”
The resulting paradox is that our bodies never evolved to function optimally without lifelong physical activity but our minds never evolved to get us moving unless it is necessary, pleasurable, or otherwise rewarding.
The four most important of these endogenous drugs are dopamine, serotonin, endorphins, and endocannabinoids, but in a classic evolutionary design flaw these primarily reward people who are already physically active.
Dopamine. This molecule is the linchpin of the brain’s reward system. It tells a region deep in the brain “do that again.”
Serotonin. This still mysterious neurotransmitter helps us feel pleasure and control impulses, but it also affects memory, sleep, and other functions.
Endorphins. Endorphins are natural opioids that help us tolerate the discomfort of exertion.22
Endocannabinoids. For years, endorphins were thought to cause the infamous runner’s high, but it is now evident that endocannabinoids—the body’s natural version of marijuana’s active ingredient—play a much greater role in this phenomenon.24
If that describes you, start by choosing types of exercise you either enjoy the most or dislike the least.26 Just as important, figure out how to distract your mind while you exercise with other things you find fun.
Entertain yourself: listen to music, podcasts, or books, or watch a movie.
Nudges influence our behaviors without force, without limiting our choices, and without shifting our economic incentives.34
Put out your exercise clothes the night before you exercise so you wear them first thing in the morning and are ready to go (alternatively, sleep in your exercise clothes). Schedule exercise so it becomes a default.
Shoves are more drastic forms of self-coercion, along the lines of my friend’s walking to avoid sending money to the NRA.
Schedule exercise with a friend or a group beforehand. You then become socially obligated to show up. Exercise in a group such as a CrossFit class. If you waver, the group will keep you going. Sign a commitment contract with an organization like StickK.com that sends money to an organization you dislike if you don’t exercise (a stick) or to one you like if you do (a carrot). Sign up (and pay) for a race or some other event that requires you to train. Post your exercise online so others see what you are (or are not) doing.
Note that all of these methods share one essential quality: they involve social commitment.
My students compete for and agree to these conditions because they know they would not learn as much without the school’s nudges, shoves, and requirements.
Young people need to move. Because our thrifty physiologies evolved to build capacity in response to demand, sufficient physical activity during the first decades of life is indispensable for developing a healthy body.
Dose-response effects of exercise on risk of death among Harvard alumni. Mortality rates among Harvard alumni grouped by age and physical activity (left) and by physical activity levels for combined age-groups (right).
(Moderate-intensity aerobic activity is defined as between 50 and 70 percent of your maximum heart rate; vigorous-intensity aerobic activity is 70 to 85 percent of your maximum heart rate.)
The benefits of even a little exercise are substantial, but the benefits eventually level off.
A number of studies have found that elite athletes, especially those who do endurance sports, live longer and require less medical care than nonathletes.11
Instead, they appear to be protective adaptations—kind of like Band-Aids—to repair the walls of arteries from high stresses caused by hard exercise.26
By some measures, a few minutes of HIIT provides as much benefit as, if not more benefit than, thirty minutes of conventional aerobic exercise, and it has the virtue of improving rather than just maintaining fitness.
A consensus suggestion is two sessions per week of muscle-strengthening exercises involving all major muscle groups (legs, hips, back, core, shoulders, and arms). Space these sessions several days apart to permit recovery, and they needn’t involve large weights but should include eight to twelve repetitions of each exercise tiring enough to make you want to stop; two or three sets of exercises are more effective than just one.40
exercise several hours a week, mostly cardio but also some weights, and keep it up as you age.
To use energy frugally, many of the genes that maintain our bodies thus depend on the stresses caused by being active.
