Mark Sisson – Primal Endurance

As you follow the traditional path of high-carbohydrate eating and chronic endurance training, you are getting yourself stuck in a round-the-clock pattern of sugar dependency and fat storage (or at least lack of fat reduction). Primal Endurance is about recalibrating your approach to endurance training and competition to escape the disastrous sugar-burning trap and reprogram your genes so that you can become a “fat-burning beast.”

Your ultimate goal really should be to achieve your performance standards in a manner that supports your health instead of compromises it, and builds your character rather than just providing an outlet for excess energy and aggression.

process oxygen more efficiently. Improving your aerobic capacity is achieved at low intensity, where fat is the predominant fuel choice, ample oxygen is available, and minimal stimulation of your alternative anaerobic (sugar-burning) energy system occurs.

When you get really good at burning fat, through sensible training and dietary patterns, you are able to go faster and faster while still staying aerobic—

You’ll have higher highs and lower lows, because this is how your body actually becomes stronger and fitter with less risk of burnout.

the overconsumption of processed carbohydrates driving excess insulin production and locking you into a fat-storage pattern.

emphasizing nutrient-dense meat, fish, fowl, eggs, vegetables, fruits, nuts, and seeds—

intensity levels. Adding strength and speed work (including not just intervals and tempo workouts, but also all-out sprints) into your regimen will make a huge difference in your ability to maintain proper technique for the duration of your endurance workouts and competitions.

Unlike many training modalities that are complex and regimented, Primal Endurance is simple, self-directed, open-ended, and intuitive. We’re giving you the skills and tools you will need to succeed, but we’re not mandating that you follow predetermined

Most importantly, we want to help you escape the destructive chronic cardio/sugar-dependency trap that you are possibly now trapped in to a mild or severe extent. We want to help you avoid the disastrous mistakes we made that compromised not only our athletic performances but also our general health, caused our endurance careers to end early, and accelerated the aging process in our bodies.

He goes on to make a specific recommendation that running two to five days per week for a total of ten to fifteen miles, at around a ten-minute-per-mile pace, is ideal for bulletproof cardiovascular health.

The most immediate triage response to escape the sugar-burning, fat-storing pattern is to slow down your workout pace into a heart rate zone that is predominantly aerobic, with little to no stimulation of the anaerobic system.

This also means that whatever endurance gifts you have were inherited just from your mother (thanks, Mom!), not your father.

Aerobic workouts have a significant impact on your metabolic function at rest, so comfortable training sessions up-regulate your fat-burning genes and down-regulate your sugar-burning genes around the clock. Slowing down your workouts helps stabilize mood, energy, and appetite throughout the day, optimizes your health, speeds recovery, and makes fat loss virtually effortless when you implement a primal-style eating pattern.

Also helpful is an Eastern-philosophy-influenced suggestion detailed in John Douillard’s book Body, Mind, and Sport that recommends breathing only through your nose to minimize the stress of a workout. If you are exercising in the aerobic heart rate zone, you should be able to obtain sufficient oxygen using only your nose, but you’ll know you’re exceeding that aerobic limit if you need to draw air through your mouth.

Running or cycling along while taking deep, nose-only diaphragmatic breaths will reduce the stress level of your workout by stimulating the parasympathetic nervous system (calming, relaxing influence) as opposed to the more common stimulation of the sympathetic nervous system (fight-or-flight response) that occurs when you conduct even a moderately difficult workout.

For example, one book referencing Seiler’s research called 80/20 Running promotes training aerobically 80 percent of the time and going fast 20 percent of the time.

During an aerobic base building period, you have to be in the aerobic zone 100 percent of the time. Going 80/20 during an aerobic period represents a dismal failure. During a high-intensity training period, you focus on maximum-effort sprints and strength-training sessions, and getting tons of rest between these explosive workouts

Your athletic pursuits require you to sleep significantly more than if you weren’t training.

minimize artificial light and digital stimulation after dark; and awaken each morning, without an alarm, refreshed and energized.

Workout difficulty should be aligned with daily level of energy, motivation, and health.

Periodization entails focusing on different types of training during specific blocks of time over a calendar year. The big picture annual periodization strategy involves an aerobic-base-building period to start the year; sequences of mini-periods where you introduce intensity, followed by rest and aerobic periods—repeated over the course of the year in alignment with your progress and your competitive goals; and finally a lengthy rest period to end the competitive season.

If you want to realize your peak performance potential, it is imperative you engage in precisely defined and focused periods of training.

Here’s what an optimal annual training pattern will look like: A strict aerobic base building period to begin an annual training cycle; brief periods of high-intensity workouts (including competitions) with greatly reduced aerobic work and overall training volume; mini-cycles where you rest after an intensity period, rebuild base briefly, and reintroduce an intensity period; and finally an extended rest period/off-season of minimal exercise and zero high-intensity sessions. This completes an annual training cycle, and you would resume a new season with an extended aerobic base building period.

Aerobic Base Period: Train at strictly aerobic heart rates for a minimum of eight weeks to begin your annual season.

That means taking a break from any kind of strength training (which is anaerobic by nature), Sunday night adult pickup basketball, and any other activities requiring anaerobic efforts.

Here’s a checklist that might help you determine the time to transition from aerobic base to an intensity phase: •   Complete a minimum of eight weeks of strictly aerobic training •   Steady improvement in MAF times (at least three tests) •   No illness, injury, or training interruptions during base period •   Optimal sleep habits where you awaken most mornings without an alarm clock, feeling refreshed and energized •   Steady energy levels and appetite at rest, throughout the entire day •   Strong motivation to introduce some intense sessions

The intensity/competition period lasts for a maximum of four weeks.

three or four days of your week will involve either total rest or short, easy recovery sessions.

Rest Period: At the conclusion of the season, you will turn off your brain and body for a minimum of four weeks and focus on the neglected other areas of your life and your personality.

In fact, that’s a good benchmark for how long your break should last: when you feel the bubbling of an underground geyser that’s about to burst if you don’t get out there and start training again.

start your season with a minimum of eight weeks of base, never exceed four weeks of intensity without a break, and always take a hearty off-season break of four weeks minimum.

First, each intensity/competition period must be followed by a period of nearly equal duration that involves rest and then strictly aerobic exercise. If you indeed complete a maximum duration four-week intensity/competition period, take at least four weeks (maybe more) that are composed of rest and aerobic rebuilding before introducing another intensity period.

Sporadic, intuitive, periodized training schedule • Align workouts with energy, motivation, health • Periods of base, intensity, rest & mini-periods • Inconsistency is key!

Going primal entails first ditching the three most offensive foods in the modern diet: sugars, grains, and highly refined polyunsaturated vegetable oils.

Next, create new habits that emphasize the nutritious and deeply satisfying primal foods: meat, fish, fowl, eggs, vegetables, fruits, nuts, and seeds.

Becoming fat-adapted entails a twenty-one-day transition period where you train strictly at aerobic heart rates and eliminate refined carbohydrates.

Sugar drives insulin production drives fat storage. The more sugar you consume in your diet, the more likely you are to store excess body fat.

Grains make us tired, sick, and fat, because we are not genetically adapted to successfully process the massive loads of carbohydrates that we ingest at every grain-based meal

We must also recognize the dangers of the prevalent vegetable oils that we have been falsely told are healthy for decades: canola, corn, soybean, sunflower, and other vegetable oils, buttery spreads and sprays, and the many, many packaged or frozen foodlike products that contain these oils.

Take comfort in knowing that it takes about twenty-one days to reprogram your genes to prefer fat for fuel—to up-regulate fat-burning genes and down-regulate sugar-burning genes.

You will assist with your primal dietary transition by ceasing any anaerobic exercise during the first few weeks in favor of comfortably paced workouts that teach your body to prefer fat for fuel at rest. In tandem, you will achieve the critical goal of moderating dietary insulin production by ditching sugars, grains, and industrial oils.

nutritious carbs like fresh fruit, sweet potatoes and other starchy tubers, quinoa, wild rice, and dark chocolate (75 percent cacao or higher) during those distinct training phases where you might need more carbs.

consider experimenting with high-fat nourishment during long training sessions (e.g., avocados, coconut butter, or almond butter), or even cutting-edge products like the high-molecular-weight, slow-burning-carbohydrate formulation UCAN SuperStarch.

try to teach your body to become fat-adapted and metabolically efficient by taking only the carbs you need to maintain your desired level of energy output and focus.

If you are not losing body fat as you desire, dial back on the carb intake for a while and make sure you don’t overeat in general, and you will turbocharge fat reduction.

occasionally or regularly extending your fasting period out to sixteen hours (11 a.m.) or even eighteen hours (1 p.m.) will deliver a host of metabolic benefits.

Being able to thrive on fewer calories is known as metabolic efficiency, and it happens to be one of the most profound anti-aging strategies ever discovered.

I also make a point to fast for one to three hours after my intense workouts to maximize the impact of the anabolic hormones that flood my bloodstream.

stuff like avocados, coconut butter, almond butter, or homemade energy bar concoctions made with nuts, seeds, coconut, and perhaps some honey for a little sweetness.

There are also some interesting cutting-edge products offered as an alternative to the usual sugary supplements taken during exercise, such as UCAN SuperStarch, a long-chain carbohydrate formula that doesn’t spike insulin; Iskiate (IS-kee-ah-tay) Endurance, an all-natural super-food concoction modeled after the legendary Tarahumara runners’ performance fuel (author Chris McDougall called it “10,000-year-old Red Bull”), and 3Fuel, a whey protein, coconut milk, and long-chain carbohydrate mixture promoted by CrossFit Endurance leader Brian MacKenzie, author of Unbreakable Runner.

Ditch grains and sugars • Emphasize satisfying primal foods • Moderate insulin = lose excess fat • Sporadic meals, honor appetite

Being in ketosis is a fragile metabolic state that requires a strict devotion to limiting dietary carbohydrate intake to around fifty grams per day. This equates with cutting out all carbs except vegetables, and perhaps tracking your carb intake with an online food calculator.

Entering and remaining in a ketogenic state entails consuming in the neighborhood of fifty grams (two hundred calories) of carbs per day on average, with some variation based

Complete your twenty-one-day transition and stick with it! Strive to accumulate at least six months of primal-aligned eating and training to achieve successful gene reprogramming before trying the ketogenic approach.

Do Another Twenty-One-Day Transition—Go Keto: This time, you are going to go full ketogenic by strictly limiting carb intake to around fifty grams per day.

If you are feeling strong and healthy, and have progressed steadily with your aerobic function over at least two months of strictly aerobic workouts, never exceeding your aerobic maximum heart rate, you are ready to add some strength workouts to your schedule

Hence, we are going to address getting strong and explosive (relatively strong and explosive that is, at a level appropriate to your endurance goals), improving your mobility and motor control under load, and thereby being able to preserve good technique and power generation even as you fatigue.


Consequently, we present the Primal Essential Movements—four of the most simple and effective exercises ever known to humankind: pushups, pullups, squats, and planks. Collectively, these exercises work all the muscles in your body and promote functional fitness for a broad application of athletic and daily life activities.

The essence of Maximum Sustained Power training is to first improve your absolute power (e.g., your highest vertical jump in a single rep, or maximum weight you can deadlift for five reps), then conduct MSP workouts that help you sustain the highest possible percentage of your absolute power for as long as possible, relative to your competitive event.

absolute power, best represented—for endurance athletes—by how much weight you can lift five times.

To conduct an MSP workout, you’ll lift your new five-rep max weight 180 pounds three or four times, then rest for ten to twenty seconds. Then you’ll do three more reps at 180, rest a bit, do two more at 180, rest a bit, do two more at 180, rest a bit, do two more at 180, rest a bit, then perhaps only muster up one rep on your final “mini-set.” That, friends, is a beautiful Maximum Sustained Power workout!

By conducting mini-sets (where you stop before total failure) separated by rest breaks, you can lift significantly more total weight in the workout.


For power development, Jacques (and most other trainers) recommends the major full-body, functional strength exercises like deadlifts (his favorite for endurance athletes), squats, and single-leg presses. “These are your primary lower body strength exercises. Power exercises would be standing jumps, stairs (sprints or jumps), plyometric box jumps, single-leg explosive jumps, and Olympic lifts,” explains Jacques.

temporary muscular exhaustion. You can focus on a single exercise such as deadlifts for the whole workout, or do two or three exercises to compose a workout.

Noakes believes that the outcome of a race (or any other activity) is what you believe it will be, and that you will use these illusory symptoms of fatigue as an excuse or explanation for the end result.


So, take the rest you need between mini sets, which will usually be ten to twenty seconds.

the muscles you are challenging. The rest between sets can extend to at least 90 seconds and up to a few minutes if necessary.

If you continue to add weight over time and again hit a point where your typical workout feels too easy, you are either still progressing to an optimal baseline weight or you are spending too much time in the gym and not enough on the road!

You metabolize fat at an accelerated rate for up to twenty-four hours after a sprint workout, according to a 1985 study in the American Journal of Clinical Nutrition.

The idea here is to integrate just a bit of sprinting into your game and enjoy huge fitness benefits.

You conduct sprint sessions only during intensity phases, and only when you feel 100 percent rested and energized to deliver a maximum effort.

The total duration of your sprint workouts, including warmup and cooldown, will be no more than twenty minutes, with the work efforts totaling up to only a handful of minutes.

For strength training, you can do some specific movements to engage the muscles in question, such as arm circles, air squats, or gentle trunk rotations, then transition into doing the exact activity with really light weight—such as squatting or deadlifts with an unweighted bar, or vertical jumps onto a lower platform.

Warming up properly for a high-impact sprint session requires that brief cardiovascular exercise to start, followed by extensive dynamic stretches and drills that prepare joints and muscles for sprinting.

Along those lines, if you feel a twinge in your hamstring or other signs of suboptimal function, pull the plug on the session like a true Olympian.

the duration of the recovery interval (how long you wait to start your next effort) should be sufficient enough for respiration to return to near normal, and for you to feel mentally refreshed enough to tackle another effort.

Consistent quality should be the foremost goal of your sprint sessions. Even if you don’t measure your time or performance carefully, it can be very effective to regulate your perceived exertion on each effort so that your last effort isn’t vastly more strenuous than your first, and to be aware of any attrition in performance

If you currently have a high fitness level and some good sprinting experience under your belt, you can try an advanced strategy of stacking a sprint workout immediately after an MSP workout in the gym—a practice called postactivation potentiation (PAP)

Recall that the Primal Blueprint recommends sprinting only once every seven to ten days, and only when feeling 100 percent rested and motivated.

Running is the most beneficial type of sprinting because its weight-bearing nature enhances the cutting up effect and the bone density effect.

Here, we’re gonna go max or go home. Consequently, try starting with efforts lasting around fifteen seconds.

you have difficulty focusing, concentrating, or even keeping your balance during a walk recovery interval, this is an indication that the nervous system is fried and that further sprint efforts are not necessary. All told, you will likely find yourself resting between thirty seconds to one minute between sprints fifteen seconds long.

How many sprints to do? How about starting with five and seeing what happens? If you can only deliver a consistent quality effort for three, then that’s where you are right now. You can deliver a couple or a few quality sprint sessions and add additional reps over time. No matter who you are, all you ever need to do is six sprints of fifteen seconds, or perhaps four sprints of twenty seconds, or some similar combination of the two different sprinting times.

When you complete your final sprint, keep moving slowly for at least five minutes, jogging if you were running

A good sprint workout takes at least forty-eight hours to recover from, so structure your strength workouts accordingly so that you can have a couple of easy aerobic recovery days after your sprint sessions.

even for devoted fitness enthusiasts. Ward off the active couch potato syndrome by walking more in daily life and taking frequent breaks from prolonged periods of sitting or stillness.

The narrow and often extreme physical demands of endurance training need to be balanced out with whole-body movement practices like yoga or Pilates that synchronize muscle groups, broaden overall strength, increase flexibility, improve your ability to focus, and deliver a peaceful, yin balance to the excessive fight-or-flight yang stimulation of endurance training.

Insufficient sleep compromises fat burning, and disturbs appetite and satiety hormones so you overeat and store the excess calories as fat instead of burning them. It adversely affects mood, concentration, memory retention, and productivity, and can lead to hypertension, increased stress hormone levels, irregular heartbeat, a compromised immune system, obesity, sexual dysfunction, premature aging, certain cancers, and heart disease

To ensure proper restoration, you must get back to an authentic circadian rhythm, synching your sleep habits with the rising and setting of the sun like your ancestors did. This means dealing with the foremost modern offenders of excess artificial light and digital stimulation after dark.

Circadian disruptors also throw off ghrelin, the primary hunger hormone, and leptin, the primary satiety and fat-storage hormone. Hence, your late nights will likely feature increased hunger along with an increased propensity to store those extra calories as fat.

In fact, if you wonder if you are getting enough sleep, you could start by asking if you are able to awaken each day, near sunrise, naturally refreshed and energized, without an alarm clock.

It’s hard to put it more plainly than this: the more screen time you engage in after dark, the more you compromise your health and restoration.

Habitual screen use after dark makes you tired, fat, and vulnerable to oxidative damage and accelerated aging. It can also contribute to degenerative eye disease and elevated risk for certain cancers. Shut the screens off ideally two hours before bedtime and absolutely no less than one hour before bedtime.

Strive to create a simple, clean, minimalist bedroom that is used for sleeping only. Absolutely no computers, TVs, pads, or smartphone screens allowed, and definitely no makeshift office setups in the corner either. Eliminate clutter such as excess clothing, stacks of books, magazines, or paperwork, or remnants of partially completed home improvement projects. Add a live houseplant to improve air quality and eliminate toxins. We are hardwired to sleep in colder temperatures, with experts recommending a range of 60°F to 68°F (16°C to 20°C) for evening sleep.

Eliminate nightlights and any LED screen emissions, even tiny ones like power indicators on charger plugs.

Strive to get to bed at a similar time each evening, something that your DLMO will facilitate for you over time as you implement good habits.

strive to wake up near sunrise.

make an effort to expose yourself to direct sunlight as soon as you wake up.

Obviously, we want disruptive alarms completely out of the picture in hopes that you will awaken naturally. When it’s time to get up, move slowly and gracefully, allowing a few minutes to sit in bed, perhaps record your resting heart rate and heart rate variability (more in Chapter 9), talk quietly with your mate, or jot down some thoughts, such as doing a gratitude exercise.

Don’t bother with your smartphone or other communication devices first thing in the morning. Exposure to news or personal communication—even if the content is pleasant—can throw you into a reactive, overstimulated mode, triggering an undesirable activation of the stress response that will contribute to burnout later.

get a special clock or smartphone app that features nature sounds and progressive tones for a gentle reminder to get up.

A brief nap of even just twenty minutes helps you catch up on REM or non-REM sleep cycle deficiencies from the previous night,

When you feel “fried” and in need of a nap, this is a literal truth, because long periods of peak cognitive function have depleted the important chemical balance in your brain cells and compromised the snappy electrical signaling needed for peak cognitive performance.

For an athlete or peak performance enthusiast of any kind at any level, even a slight deficiency in sleep is highly destructive to your goals and your overall health.

One Mayo Clinic study revealed that a leisurely (1 mph) fifteen-minute walk after a meal lowered by half the two-hour-long blood sugar spike that occurs after a typical meal.

Dr. Levine cites research that performing an activity as simple as standing up at your desk instead of sitting increases caloric expenditure by 10 percent, while taking frequent movement breaks during the day can add up to an additional thousand calories burned or more, as well as promoting hormonal changes that encourage fat burning instead of fat storage.

Katy’s favorite form of movement nutrition is walking, and she believes you should walk anywhere and everywhere you possibly can.

Brain science confirms that we are simply incapable of sustaining intense focus for longer than twenty minutes.

Ideally, your breaks will expose you to fresh air, open space, and direct sunlight to energize your body with electrically charged air particles called negative ions.

For every two to three hours of diligent cognitive effort, you should take a longer break of fifteen to twenty minutes where you change your environment, do some significant physical movement, and perhaps perform some specialized exercises to counterbalance the time your body has spent in fixed positions.

Stretching, foam rolling, preventative or rehabilitative exercises, yoga, Pilates, and other cool stuff that most endurance athletes “don’t have time for” can mean the difference between peak performance and health, and injury, burnout, or technique dysfunction.

Yoga, Pilates and other programs focused on flexibility, balance, and stretching help balance the extremely repetitive and narrow movement planes of traditional endurance workouts.

Because of your improved proprioception honed through deliberate movement practices, you will be able to better notice and correct when your technique does falter on the road.

Building awesome core strength through yoga or Pilates will generate a noticeable improvement in your technique in a very short time, and will help prevent common injuries to the lower back and ham-strings that are triggered by a weak core

Brown presents evidence that play, across the span of a lifetime, literally shapes our brains—forming new connections, creating new circuits, and organizing existing connections. The free-flowing, risk-free nature of play allows us to test out skills and scenarios that prepare us for real-life challenges.

When humans are deprived of play they can suffer from multiple dysfunctional symptoms, including lack of curiosity, diminished social competency, and uncontrollable emotions.

here are some tips and aids you can use to recover from training stress as fast as possible: Cold therapy, compression, hydration, movement, refueling, the new RTX cooling glove, self-myofascial release, and last but perhaps most important, sleep!

When you apply ice to an inflamed area, you inhibit the function of the lymphatic system in clearing toxins out of the injured area, potentially delaying your recovery and even interfering with your ultimate ability to adapt and become stronger from training stress. Dr. Starrett and other thought leaders are swapping out the familiar RICE (Rest, Ice, Compression, Elevation) acronym with a new one called ECM—Elevate, Compress, and Move—as the best way to heal injured or overworked tissues. The ECM protocol helps increase bloodflow to the injured area, supporting the hardworking vascular and lymphatic systems in clearing out toxins and accelerating the healing process.

Instead, it is believed that exposure to cold after workouts might provide more of a psychological benefit than a cellular benefit.

The refreshing sensation of cold exposure has a profound psychological impact that cannot be discounted when you are looking to speed recovery,

Some experts mention an ideal water temperature range of 50° to 60°F (10° to 15°C), and an ideal exposure period of five to ten minutes—never exceeding ten minutes at 50°F or below.

Compression gear such as tight socks or wraps enhances the ability of the lymphatic and circulatory systems in clearing out the extracellular waste products and excess fluid that accumulate in tired muscles after strenuous workouts.

Hence, a post-workout recovery strategy might be to plunge into a cold river for a few minutes, throw on some compression socks, and hang your feet on the edge of the couch while you watch a show. Over the ensuing hours, frequent brief walks would ideally break up extended lounging periods.

Rehydrate immediately after workouts, so you can ensure the body’s recovery mechanisms kick into gear right away.

Add a pinch or two of sea salt if you are drinking plain water, or consider a naturally electrolyte-rich beverage like coconut water. Don’t bother with the colorful sports drinks loaded with chemicals and added sugars.

If you make an effort to move more frequently—even for a few minutes at a time and especially in the hours after your workout, you will soon notice that you are a more fluid, flexible, and energetic human at all times.

Eat something real and nutritious within an hour after your workout. My favorite post-workout recovery meal is a salad. If you’re pressed for time you can make a recovery smoothie, using whey protein powder and natural ingredients like fruits and vegetables.

The tremendous popularity of foam rollers and therapy balls and other torture contraptions used for self-myofascial release is a testament to their ability to speed the healing of tight or stressed muscles through deep, dynamic compression.

Keep in mind that a finely tuned, mobile, flexible physical specimen should not experience pain anywhere on the body, even when pushing or rolling tissues with significant force.

If you do experience pain in certain areas—and it’s highly likely that you will—this is an indication that the area needs myofascial release.

Take what your body gives you every day and nothing more. Remember, it’s always possible to go to the well and force things to happen unnaturally—we’ll discuss this in detail in Chapter 10—but you will always pay a long-term price for an unnatural, imbalanced approach. Focus on enjoyment of the process of becoming fit—even if things don’t work out exactly as planned—and resist the temptation to drift into an obsessive/compulsive, outcome-oriented mindset.

When the parasympathetic and sympathetic factions of the autonomic nervous system are working in harmonious balance, you have a greater variation in beat-to-beat intervals, delivering a high HRV score. When you are under stress and thus sympathetic dominant, your heart beats in a more metronomic fashion, leading to a lower HRV score.

To get started with HRV monitoring, obtain an HRV reading each morning before getting out of bed, taking care to assume a completely relaxed body position and mindset. Spend a few minutes to allow your values to stabilize and then archive the data with the push of a button. Over a period of months, you will see your HRV values land into a normal “baseline” range that’s indicative of you feeling rested and recovered.

With a reliable baseline established, you can be alert for trends of lower-than-baseline values, which are associated with overstress or insufficient recovery. You’ll also have occasional days where you generate numbers higher than your baseline, suggesting you are exceptionally relaxed and recovered!

Ideally, you would like to see a high HRV score (parasympathetic and sympathetic nervous systems working in balance), a high HF value, and favorable LF:HF ratio (stress response and stress hormones moderated/optimized), and of course a low resting heart rate.