A bi-weekly interactive health & fitness library.

Here we go: the transition from Q-3 into Q-4, or what I like to call: the second great “fitness valley” of the year. In 8 years of coaching hundreds of busy working people, I observe trends and patterns across most clients. The first great fitness valley of the year is January-April. We return from the holidays and travel, the kids are back in school, and work starts to pick back up, providing us with some rhythm to build our health routines around. The next great fitness valley is right now. These months (September-November) tend to be one of two times of the year when clients tend to be most consistent. We’re back from summer vacations, work (structure) resumes, and kids are finally out of our hands again during the day…but only a few short months before the holidays throw the train off the tracks again. Consider that this valley is also one month shorter than the other major FV of the year: the Jan-April window, largely due to so many holidays, and the sun starts to set earlier in the day. There’s not much else to do but go to the gym, work, and go to sleep early.

If our primary goal is visual progress, consider that any CONSISTENT change we make now, we will only start to see a ‘lasting’ change in the body in a minimum of 3 months. Why? That’s how long it takes for a true, solid adaptation to be visible. Muscle takes time to grow. Any fitness magazine or shredfluencer program that promises a big, firm glute shelf or ripped abs in 3 months is straight-up lying to you. Prior to this, we may see what looks like change, but is actually just an acute, temporary physiological response: the fleeting “muscle pump”, leaning out due to dehydration, or smoke and (literal) differences in mirrors and lighting. So, lettuce dance into this fitness valley with aplomb. Read on….de

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The last two weeks of August. NYC feels deliciously empty. You can actually get a squat rack at Pure Gym. You might actually see someone who’s lived in the West Village since the 60’s, instead of a sea of matcha-wielding Lululemon Pilates influencers and drunk finance bros in white Alo hats. We’ve completely forgotten what it feels like to wear pants. We return home from long walks with soggy this or that. Our bathrooms look like 19th-century clotheslines. Nothing dries. Time slows down.

Many of us struggle to maintain some semblance of weekly training while away on vacation this time of year. What I tell my clients: fold your weekly movement into time spent with loved ones, or doing things you love. For one client, that could be taking long walks on the beach while away at Fire Island. For another, it could be hiking with their girlfriend, or rowing on a lake in Austin, or cycling in Iceland. For others, it may mean finally having some time to hit the gym more consistently at home in NYC because work finally slowed down with their boss being away. For me, it’s meant having to lean into shorter workouts while taking care of some family responsibilities and growing my training business. Some of my lifting days are as short as 15 minutes, others as long as 45 mins. Training with minimal equipment allows me to stay on the beam at home some days. Learning how to do more with less sets you up for success when you go away on vacation, as we tend to do this time of year. Variability wins…

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There is no such thing as “good posture”. The purest biomechanical definition of posture I will argue is: whatever position joints spend the most time in, that the nervous system has adapted to tolerate. You can have forward head, kyphotic spine (hunchback), internally rotated shoulders, anterior pelvic tilt, or any number of other postural “imbalances” that do not create pain or affect how you move. You can also have any combination of those that ARE POTENTIALLY linked to biomechanical limitations that cause pain. Only what causes pain or an unwanted effect (slower pace, aesthetic desire) is worth correcting, but not all are possible to correct.

Forcing holding posture creates more problems

Simply hear the word ‘posture,’ and you’re likely to immediately sit up straight, suck in your gut, puff out your chest, pull your head up, and tuck your chin in. Companies sell devices that remind you to do this, or uncomfortable bra-type slings that compress your body into what we think is ideal posture. The problem with these approaches is they don’t address the contributing root causes of “postural imbalances”, which are mostly due to a lack of the ability to either MOVE OUT OF or REMAIN in a position without discomfort. These factors are mainly a combination of highly nuanced structural, neurological, and muscular variables. The goal is to improve how these systems interact ACTIVELY (exercise) so that they remain that way PASSIVELY without the need for constant conscious correction. That being said, there is never a single root cause, and no one can ever tell you with 100% confidence that any single variable is causing your pain because of the infinite complexity of the integration of the human body's systems. We still do not fully understand the sympathetic nervous and GI systems, for example. Still, we do know enough about how the CNS/PNS works to improve postural desires with simple strength training exercises that don’t require immense drags on our time or money.

Think of ideal posture like a crumpled shirt

Visualize a button down dress shirt sitting crumpled up on your clothes chair. Yes, THAT pile of clothes chair. It won’t get wrinkled if it is temporarily draped and folded on the couch, but if it stays balled up for a day or more, it will become wrinkled. Your posture is basically this. No single position is pathological: you can slump in your chair after lunch for 30 minutes, but if you sit like that for hours or worse—for weeks—you’ll suffer compensatory pains. Now imagine that shirt remade in a wrinkle-resistant fabric. That is what becoming stronger and more mobile does.

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How do you stay in shape when smoke chokes the skies, dookie lettuce gives up explosive diarrhea, and even frozen blueberries aren’t safe from E Coli strains? All we got were a few weeks of Knicks and World Cup optimism until the news ticker snapped back into doomsday mode reminding us we live in an apocalyptic hellscape. Solution? Pixelated song lyrics.

Confession: I “tumbrlfy” my morning workouts. I’m a 40 year old man that still uses tumblr. My physical therapy doctorate program requires me to work out early mornings before my clinical rotations, and I suffer from ADHD, which means I don’t wake up with as much dopamine (neurotransmitter responsible for movement and focus) than other peeps. I’ve always been a visual person, so sometimes all it takes is seeing blurry concert photos of my favorite musicians playing athletic live sets to inspire me to get moving. A quick glimpse of Trent jumping on speakers and breaking stuff is usually enough to get channeling my inner pathos into raw kinetic energy.

Social media platforms are usually at their best when they’ve run their course and deviate into graveyard energy with virtually no revenue potential. That’s the tumblr jouissance. Trash your inner Yamaha DX-7 synthesizer and get moving.

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Post Knicks jubilance + pride + world cup + incredible NYC gov election results + 4th of July travel = an incredible blossoming of summer, but….a rough time for consistency for many clients. Staying on the beam becomes a lot easier if we understand what the most impactful physiological variables are. I would say these are the most relevant areas to focus on during the summer months when (nourishing) social distractions are at their peak:

1. Alcohol: liquid calories are always going to make the most impact any time of year, but cognitive fog, impulsive nutrition choices, low energy, and poor sleep may not be worth more than 1-2 drinks a week.

2. Sleep: big weekends tend to derail weekday training. Maintaining some semblance of habitual bed timing weekdays gives us a buffer against the late nights we’re likely to have. Sleep masks, investing in a blackout shutter, and getting more strict on bedtime phone habits make a difference.

3. Less is more; this is not the time to chase PRs. Now is a good time to lean into a more versatile training schedule, training at home some days with dumbbells (vs the gym) and leaning into single limb exercises on days hangovers, poor sleep, or work spikes rear their ugly heads.

4. Don’t fall for the cardio trap: many clients are tempted to give up weights in favor of doing cardio as temps rise. Structured cardio will only ever amount to 5-10% of our caloric expenditure, and that is mostly going to be for conditioned athletes. Stay on the path of consistent weight training to ensure you continue to build the muscle needed to improve your metabolism.

As for more holistic deets….read on:

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Two weeks away from summer, and two days into my next physical therapy outpatient orthopedic clinical rotation, and I’m already noticing a pattern: many of the injuries and pain presentations I’m seeing might have been prevented—or at least made less likely—by getting stronger. The challenge is that getting stronger is also one of the most common times people experience pain, flare-ups, and injuries. The question becomes: how do we build strength without getting trapped in that cycle? The answer is usually more complex than simply “exercise more.” A person deadlifting with poor mechanics may develop sciatic symptoms, not necessarily because deadlifting is harmful, but because tissues and movement patterns have not adapted appropriately to the demands being placed on them. In those cases, a skilled physical therapist or coach can help someone learn the difference between a true hip hinge and excessive lumbar flexion, gradually improving movement quality while continuing to build capacity.

Many common diagnoses—non-specific low back pain, patellofemoral pain syndrome, sciatica, and shoulder impingement—are often treated as if they are the root problem. In reality, they are usually descriptions of symptoms rather than complete explanations. Frequently, these conditions exist alongside deficits in strength, endurance, motor control, mobility, recovery, or training design. When we receive these diagnoses, it is easy to freak out and interpret that as something is permanently wrong with their bodies. More often, they reflect a mismatch between what the body is being asked to do and what it is currently prepared to tolerate. The solution: a thoughtful assessment followed by a progressive plan that addresses the underlying deficits within a STRENGTH TRAINING program.

Over time, gradual exposure to movement, improved technique, and progressive strengthening can change the picture dramatically. As the glutes, core, hamstrings, and other supporting musculature become stronger and more coordinated, movement often becomes easier, and symptoms may become less threatening. The nervous system becomes more tolerant of previously sensitive movements, neural inhibition lowers, hip mobility improves, and daily activities feel less restricted. This process is rarely quick, but it is repeatable. The people who tend to succeed are not the ones searching for a perfect exercise or a magical treatment—they are the ones who consistently build capacity over months and years while adjusting their training intelligently when symptoms arise.

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I’m finally starting to see the “SUMMER BODY BUTTS & GUTS GET SHREDDED OR DIE” reels fade into obscurity as we slide into the swamp shorts temps in NYC. I’ve been away for a week in Cali and forgot that parts of the world exist where the parts of our bodies that droop and bounce don’t get glued to our epidermis (I was in San Luis Obispo for a wedding where there’s no humidity like, ever). Now I’m in Dallas with family for a week, and I’m sweating balls from head to toe right out of the shower.

IN ALL SERIOUSNESS, being back in mid/nor-Cal after like 15 years away made me forget the design language that part of the country operates within. Peep this street sign. It’s funny to me as someone on a long educational path in healthcare because it has a wellness charm sort of baked into it, but also has a kind of subtle medieval dark undertone in a middle earth Frodo Baggins frolicking in the produce center of America kind of way . I like to call it “slow hippie gothic”…

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Pseudo-spring melts into pseudo-summer melts into…35º-85º temperature swings as wild as an alliteration a professor recently taught us to remember symptoms that hydrocephalus patients (swelling of fluid in the brain/spinal canal) display: “WET, WACKY, AND WILD”.

Wet: urinary incontinence

Wacky: executive dysfunction, erratic behavior

Wild: gait disturbances, poor walking patterns

Nothing like 50-degree temperature swings in 24-48 hours that make you question every item of clothing in your wardrobe and make you 15 minutes late everywhere you go. There’s a (somewhat problematic) 2009 Rick Owens quote about this:

Anyone who’s followed him for years knows he’s frequently contradicted himself (as anyone eventually does that does anything interesting), but there is some truth that the feeling of confidence in our bodies that training imbues is worth far more than spending hundreds, if not thousands, on a new wardrobe every season due to our clothes not fitting how we want. It’s now 2026 and not 2009, and thankfully, there’s now a lot more platitudes of what a fit body means and looks like (he then went on to cast models of a variety of body shapes and ages in several runway shows since 2009). Confidence doesn’t necessarily mean physical changes either. Sometimes it’s simply the psychological fortitude we feel gained from lifting heavy things often enough.

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Ah, spring equinox. Longer days of sunlight that make evening workouts slightly more feasible, and sunrise workouts don’t feel quite as much like climbing the flights of stairs in your walkup while hungover…at least until the summer Fridays start. But we’re not about that life so much nomo because…we getting too old to day drink. At least I can speak for myself; it’s been 10 years since I drank, and I’ll be 41 this year. The dumbells aren’t getting any lighter. I can happily report that I hit a near 8 mile pace on a 12 mile run this morning while training for the Brooklyn half marathon, so the trade off is def worth it. How did that happen? The proof is in the pudding…

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Not me. I walk around in a groggy mental fog UNLESS I work out first thing in the morning, because exercise wrings the brain like a sponge, moving the secretion cycle earlier in the day to match the psychopathic hours that men (those largely in power) force us to work within in our capitalistic conception of time. Why does our workday most commonly have to start at 9am, or even earlier at 7-8am, in the fields of healthcare and construction? The hours were created by men when they dominated most fields of work. I have a theory about this, that the hours were created this way to suit their hormone secretion cycle…at the expense of everyone else, including some men. Testosterone is secreted during the last few hours before we awake, and is in a more steady supply in men than women, meaning the first few hours of the day are going to be when it has the most overlap with working hours. Women tend to need more sleep than men due to fluctuations in estrogen and progesterone across the menstrual cycle, which affect sleep regulation, REM sleep, body temperature rhythms, and fatigue. A 7-9am start benefits few people across the entire spectrum of gender when we think about the fact that only 25% of American adults meet the federal physical activity guidelines for both aerobic and muscle-strengthening activities, according to CDC data. While roughly 47% meet aerobic standards alone, approximately 75% fail to meet both recommendations. In 8 years of coaching hundreds of clients on a very personalized level, the number one problem quoted is lack of time.

Let’s jump back to the hormones and neurotransmitters—the sexy stuff. Both weight training and cardiovascular exercise secrete dopamine, serotonin, acetylcholine, norepinephrine, and cortisol. These are all neurotransmitters and hormones secreted by the brain that allow us to focus, execute complex executive thinking, and retain information. If you’ve ever worked out before work consistently for at least two weeks straight (long enough to start GETTING ENERGY from exercise after your neurotransmitter cycle has adapted), then you know the feeling I’m talking about. You’re simply dialed in; time feels fluid, you can make executive decisions more easily, you tackle those emails instead of marking them unread, and you can lead a 9am Zoom meeting with fewer ‘umns’ and ‘uhhs’. That all sounds great, but how do we get to doing this habitually?

I started slowly

The biggest obstacle to getting up earlier was alcohol. I had already had success cutting back on it to mostly 2-3 drinks a week, but I was heading into my late 20s by then, and even a glass of wine made me groggy the next day. One day I realized that the way I felt after lifting weights was about as good, if not better, than a mild buzz and had no side effects. That AHA moment meant that alcohol had to go for me, and I had been working on putting together other pieces of the wellness puzzle: therapy, volunteer work in a community, and nutrition that gave me a sense of purpose and reduced my need for substances. The next biggest hurdle was getting to bed earlier. I was working in an extremely high-stress role as a senior producer, about to step into a director position in advertising. I was working 50-60 hour weeks with frequent travel. The ONLY way I was getting a workout in was if I was putting it first thing in the morning. Emails frequently poured into evenings, and the few days I did manage to get to the gym after work had me struggling to shower, make dinner, and get to bed at any reasonable hour to get up on time for work the next day. Working out after work and weekends also meant fitting in a date, time with a friend, and keeping up with chores was almost impossible. I realized I had to build my life AROUND my health + fitness, not the other way around. It meant I had to put exercise first. It still means that, and will need to mean that for the rest of my life. Here are the tactile things I started doing that I still do today:

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We’ve had like two spring peakaboo moments over the last 2 weeks here in NYC (by Spring I mean anything over 20ºF) and I’m seeing quite a few clients start re-emerging out of understandable periods of inconsistency due to SAD, Q1 work burnout, and the realization that the New Year’s sprint doesn’t last much longer than mid February unless there’s some tweaks to make training more consistent; namely my hybrid approach you may have seen me hollering about on IG: working out at the gym a couple days a week when we CAN get there, and from home a couple days a week when we CAN’T get there. THIS is the solution I’ve found works for the vast majority of real people between ages 27-50 that aren’t influencers (just about anyone reading this)…a period our lives that is a grind time. We’re starting businesses, having babies, reaching seniority in our careers, going back to grad school…in other words, we don’t got shit time to be doing programs written by bodybuilders on steroids. We need realistic solutions to real ass problems. Read on…

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So it’s still blown out frozen wasteland winter mode out there on these NYC streets. You been wearing the same funkly ole lentil soup stained hoodie for days OK maybe the hoodie is just me) and haven’t been to the gym since…Novembruary 7th. Yes: Novembruary: the combination of November— (the last time we might have been consistent before the holidays wiped out our training stride)— and February (we thought we would be on the beam by now, with New Year’s resolutions now fading into the shame spiral). Lettuce not lament the reality of life in 2026: it’s a messy maelstrom of dooksteaming social feeds as bad news bombards us 24/7. HOW do we find our strength in the dook? We consider that life throwing shit is a renewable energy source. We channel the shit into rage, and rage = fuel. Pick up the heavy thing and put it back down, and then do it again a few more times and see how you feel. Hello, dopamine, my old friend….

Read further :)

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NYC is a frozen blasted wasteland and half my clients are struggling with staying active while spending more time indoors than they’d like. Chances are you’re reading this and feel similarly, even if you’re not in NYC. January is a tough month: we’re now back into the avalanche of post-holiday work as the Q-1 corporate grind slurs into a dance uglier than your weird uncle at that wedding you didn’t really want to go to (this is like, the year EVERYBODY decided to get married…most of my readers are between 30-45). Spring is around the corner and we don’t to emerge from hibernation looking and feeling the effects of a long, colder than usual winter, so what do we do? We get creative with combining fitness with work (especially at home), we educate ourselves (tis the season of more time for reading), and we keep it casual, yet consistent. Read on Flux fam:

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Despite this, there are notable drawbacks to a weekly fitness flow that centers on Pilates as the ONLY form of movement. While no single modality (strength training, running, yoga, etc) can check off all the major health buckets, if we have to choose one, there is a strong argument for centering strength training with progressive overload as the modality with the widest health benefits (cognitive function, bone density, muscle mass, metabolic health, and minor cardiopulmonary gains). Still, Pilates does have a place within the limited time crunch that my clients in major cities like NYC and LA tend to struggle with. Why? Say less…

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A bi-weekly interactive health & fitness library.

PEOPLE OF FLUX WORLD: I’m back. If you’ve wondered where I’ve been, I took a 6-month break from social media to focus on my physical therapy doctorate and my ~15 private remote retainer clients. Billing was paused during that time, and the newsletter will return on a bi-weekly basis just as before.

Only those who have gone through a medical degree, or have a loved one who has, know the sheer brutality that is week after week of SPIRITUALLY ERODING exams 🪖. You have several 2-3 week spans with 8-10 exams that require weeks of prep. There were a couple of stretches where I didn’t have a day off for 2 months straight, with 2 hours of commuting round-trip. Needless to say, I had to smash the pause button on my social outreach to stay locked in on this biz investment and (painful at times) period of growth.

This time of focus also marked a major chapter in my 7-8 year journey to become a doctor of physical therapy: I had what we call a “white coat ceremony” in medical professions. It marks the completion of almost all didactic studies and the start of clinical rotations treating patients. I’m currently about 1 year away from graduating and obtaining my license to treat patients as a far more comprehensive expansion of my research on the limitless complexity of the human body. This past semester featured curriculum on prosthetics, advanced stroke rehab, post spinal surgery rehab, & more.

An unfortunate misconception about physical therapy is that it’s just massage with heat and ice slapped on and 3 sets of 10 leg raises. While there are some PTs that operate McRonald style clinics with 30 min sessions chasing sheer volume, the vast majority of PTs use the knowledge gained from studying every system in the body: cardiopulmonary, GI, endocrine, lymphatic, renal, reproductive health, and most importantly the nervous system (which is a major distinction that sets us apart from Chiros: no shade, just differences).

HERE WE GO AGAIN: A fresh batch of Q&A from the archives…

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The newsletter format allows me to share glimpses into these studies offer practical applications relevant for busy working people tryna stay fit in dark times like these. I went back to school at the age of 34 to tackle a 7-8 year med school degree because I believe that fitness is truly one of the most militant form of resistance we have going into a period where access to healthcare is being demolished and privatized in what is likely to be the largest transfer of wealth to the 1% of insurance lobbyists and ruling oligarchs to date. Fitness has always been, and is going to be even more so the most anarchic, most empowering and autonomous gift we can give ourselves and our communities. I greatly appreciate the interest of my paid subscribers during my continuing education grind.

SO, FATIGUE: why you’re so gotdamn tired all the time and use the phrase “my last two braincells” more often than you’d like to admit. Congratulations: you live in 2025. A constant barrage of digital detritus bombards your phone, laptop, iPad…pretty much any device just shy of a half dead Tamagotchi. The noise level pervades nearly every minute of your precious 16 waking hours a day…hours of your life that you’ll never get back, gone forever. Not even your Microsoft dashboard is safe from the latest dumbass Trump vomitus. Your reels feed is a war zone of ads for ill fitting t-shirts from struggle brands that will be gone in 6 months, gooncel targeted clickbait slop, ragefluencer dramagasms, and plenty of cute animals (thank mf god for at least that). Genocide is broadcasted daily, paid for by our tax dollars. All of this is stimuli our nervous system has to chug neurons to process. There is a cost to this in regards to the energy we might devote into more nourishing aspects of our lives and our communities: all of this cacophony generates some level of fatigue. There’s a (fake) buddhist proverb for this: “The trouble is, you think you have time”.

What does this have to do with getting in shape? WHAT THEY DON’T TELL YOU ABOUT WEIGHTLIFTING: the single most important concept we need to embrace is the sustenance of our nervous system to mitigate fatigue. It is the make-or-break concept that can mean working out for months, even years, and not seeing or feeling progress in body composition, strength, athleticism, even flexibility. This is antithetical to the “more is more” super-size me McLifting maximalism that most of us reading this grew up with in the 80’s, 90s and 2000s…the last decades of so called “American exceptionalism”. The point of contention this article focuses on has to do with the concept of ‘volume’ in exercise terminology. Volume is the total amount of work performed in a training session, over a week, or across a training cycle. Volume, is the idea that more is always better. High reps, high sets, simply brutalizing the body until we’re too sore and exhausted to train any longer. The problem is, we live in a society of more of…everything turned up to 11 on the excitation dial all the time already. The key to managing fatigue in our training is embracing the fact that some level of it is inevitable. Our nervous system is under constant excitation processing auditory, visual, and sensory stimuli at all times, including while we sleep. Light hitting our retinas generates a certain level of fatigue. Digestion, even the simple autonomic act of breathing. To fatigue is to be alive, which is to embrace the reality that we are not superheroes. We can only train as hard as we can rest and recover.

in exercise physiology terminology, volume is often quantified by:

• Total weight lifted (load × reps × sets)

• Or total repetitions completed across sets in one day.

• Or total duration of time working the same musculature on the same day.

• Or the total duration of time training within the same modality over a week (total amount of time spent doing cardio vs weights etc).

We grew up in an era of ‘sweatsensationalism’, messaging that told us we didn’t train hard enough if we weren’t completely destroyed by the end of the workout. The problem with this idea is that is both inefficient as a lifestyle and has detrimental physiological effects. How many hours a week do you realistically have to wash your hair after a sweat drenched cardio session? Transition from a grueling run right into a Zoom meeting at 9am? Somehow spend two hours at the gym you can steal those away from your kid, or finish work in time to go workout and then go on a date? Intensity is important, however. We need to train smarter and harder, but it needs to be in a way that doesn’t completely deplete our battery so we can show up more often throughout the week. This especially also means not training as long as we might think within a single workout. There are rarely any good reasons to workout for longer than 50 mins to 1 hour, assuming we are airtight in setting up and breaking down equipment during our rest periods, have a well designed workout program, etc (which should be the goal when we train if we want to make any kind of lasting progress). The exception is for those training for long races, so I’ll leave endurance training out of this conversation and focus mainly on training for hypertrophy, strength, or mobility.

'Rose bleed,' 2003, Gabriele Horn and Ruth Ronen, 2008

Thankfully, frequency is what maters more than total volume. Frequency is how often we train different muscle groups spread out across a week instead of more time working the same muscles on the same day. I have some days where I only lift weights for a mere 15 minutes: 2 sets total of lunges, 2 sets of calf raises, and 2 sets of glute bridges (all with very heavy weights) done as warmup before going for a 25 min run. This breaks up my overall weekly training volume in a much more economical use of time, netting me both mobility and hypertrophy gains. I’ll train the rest of the muscle groups in my legs across 2-3 other full body days. This is much more efficient than doing an hour of entirely legs—often with lighter weights—because the long duration ends up fatiguing us, reducing how much we could lift if we did less volume. This bears the next question: But but but…isn’t that 15 minutes like…not enough? No. Science time….

Central nervous system (CNS) fatigue during weightlifting primarily involves reductions in the central drive from the brain through the spinal cord to motor neurons—the cable that ‘zaps’ the meat (muscle) with an electrical charge to get it to contract (move). Prolonged or intense training leads to altered excitability of cortical (brain processing) areas, reducing firing rates of these neurons, and increased activity of inhibitory circuits (nerves that tell muscles to chill). This results in decreased descending output through the spinal cord, lowering the ability to sustain maximal voluntary contractions against resistance (weights). Additionally, the brain’s integration of sensory feedback (think: noise through the net sum of all of the joints in the body and skin receptors making contact with whatever is moving) can reduce motor output (think: a million trump news notifications happening over a cascading flow of microseconds), effectively reducing how much we can lift. Psychological factors, such as reduced motivation and perceived effort, are also processed at higher CNS levels, contributing to central fatigue. This means that psychosomatic stressors (hello stress, the news, the date that ghosted you) also drain our CNS.

Motor unit recruitment (how many muscle fibers we can ‘turn on’ to lift a barbell) also follows a physiological law called Henneman’s size principle, which states that smaller, fatigue-resistant motor units (slow-twitch, usually postural and smaller muscles) are recruited first, with progressively larger, more powerful, but fatigue-prone fast-twitch motor units (bigger, more powerful muscles like quads) engaged last as load demands increase. During intense or prolonged lifting, peripheral fatigue within the muscle itself occurs due to reduced excitability at the neuromuscular junction (dampening the strength of the electrical impulse ), all of which diminish the muscle fiber’s contractile capacity. All of this reduces our overall force output, meaning…long workouts basically water down our individual exercises.

Then there’s the other part of fatigue which is more related to the metabolic (energy system) debt accumulated through long, inefficient workouts. During repeated or high-intensity contractions, the rapid hydrolysis (breakdown) of ATP leads to an accumulation of metabolic byproducts such as inorganic phosphate (Pi), ADP, hydrogen ions (H+), and lactate (waste products). Excess H+ from anaerobic glycolysis (our fastest, heaviest movements) lowers intracellular pH (making the body more acidic) which also depresses enzyme activity and disrupts excitation-contraction coupling (muscles don’t contract as easily). During weightlifting or any form training, our muscles need a steady supply of energy in the form of ATP (the main fuel source cells use) to contract and generate force. This energy primarily comes from breaking down glycogen, which is the stored form of glucose in our muscles. This is mostly derived from carbs, and is the reason why you have shitty workouts that don’t build muscle on keto or other low carb diets. Once glycogen is broken down into glucose, it enters glycolysis to produce pyruvate, which then feeds into the Krebs cycle within the mitochondria (cell factory). As you continue lifting, your glycogen stores gradually become depleted, providing less fuel for this cycle and leading to reduced ATP production. Creatine is the stored form of phosphate needed to power quick contractions, and is why every fitfluencer on earth suggests we take it. Additionally, intense exercise can cause a buildup of byproducts of lactate when the body relies more on glycolysis without adequate oxygen, contributing to the burning sensation and muscle fatigue. We may mistake this burning to mean: wow I’m training so hard I must be building muscle! The reality is this is just a result of a muscle crapping out as a result of a hitting an endurance threshold. There is no direct relationship between hitting this threshold and muscle growth. We will build muscle more effectively with fewer, sets, fewer reps, but with heavier weights because we will reduce the fatigue and muscle damage both within the workout and in the following days. We can build muscle in as one set taken to failure, and is why I have most of my clients do no more than two working sets (not including warmup sets) per exercise. Instead, I encourage them to utilize progressive overload (increasing the weights as often as safely possible), and to workout more frequently throughout the week, in shorter, more intense workouts, typically in the 40-50 minute range.

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Flux fam: I’m back after taking 3 weeks off to focus on my doctorate studies and client work. Billing was paused during that time. I’m back with news that Flux Codex will move to a biweekly publishing schedule. It will allow me to make each newsletter more comprehensive. If you follow me on IG, you may have seen that I’ll be using that platform less. I’m finding that the app is less and less conducive to providing thorough health and fitness advice, and has become an app where only quick jabs garner engagement: insults, rage-bait, and/or flat-out misinformation. So I’ve decided to use my time to make each newsletter more structured around a specific topic informed by my ongoing doctoral studies, and include more practical solutions on how to make fitness work within a busy schedule. It will still include selections from the archive of AMA’s from time to time.

This week’s letter focuses on cardio Zones. It’s a tricky topic with a lot of nuance. While ALL cardio zones have health benefits, not all have the same health benefits, and have some pros and cons when it comes to integrating them into a packed work week. I’ve had to shift my relationship to cardio this year due to time constraints:

If you were born sometime before the mid 90s, you probably associated fitness primarily with cardio at some point, or still do. Those of us old enough to remember 9/11 had borderline harmful messages like “run 50 miles a week to lose weight” blasted into our domes by the aerobic industrial complex of magazines like Cosmopolitan, nagging family members, and early exercise DVDs. But what exactly is cardio, and how much of it do I need to stay “in shape?”. What does being “in shape” even mean exactly?

The American Heart Association (AHA) defines exercise standards as:

These 150 minutes can be 150 minutes per week of moderate-intensity aerobic activity or 75 minutes per week of vigorous-intensity aerobic activity, or a combination of both. As a coach who works with clients on a highly personalized level, I have a window into the averages that most working people actually manage to accomplish. Here’s the reality: very few of us (myself included from time to time) meet these standards. Most clients find that 2-3 days of weightlifting aren’t too challenging to maintain once we iron out a few respective lifestyle and mobility needs. They’re able to do this in the convenience of home, even in cramped apartments here in NYC, using a set of adjustable dumbbells and a few other pieces of minimal equipment. They fire off emails in between sets during rest periods, and can rally through a groggy morning. Others find that grinding at the gym isn’t the most cumbersome challenge after work: it’s a space deigned to facilitate separation between work, rest, and fitness. Most find that interrupting the flow of their day with a solid block of at least 30 minutes of sustained cardio is much harder than anticipated. Why?

It isn’t so easy to transition from a 25 min sweat soaked run into a Zoom meeting while out of breath. Or drag a road bike into the office after 40 minutes of cycling down the long route to work. Or have to book in an extra hour that doesn’t exist in the day to wash your hair. Cardio tends to require hitting the pause button on our slack message, email-saturated, social media addicted attention spans in a way that is much easier said than done and maintained week after week….for the rest of our lives.

So, how do we make it work? The key lies in understanding cardio “Zones”…

Cardio training is typically divided into five zones based on your heart rate as a percentage of your maximum heart rate (calculated roughly as 220 minus your age). Each zone offers unique health benefits across various categories such as fat loss, endurance, heart health, mental well-being, and metabolic function. Understanding caloric expediture for each zone requires understanding how our bodies use 3 different energy systems to produce movement.

We want to look at this like a spectrum of energy demands:

1. The Phosphagen System uses stored ATP and phosphocreatine (PC) as the primary fuel source. That word ‘creatine’ is the same creatine that fitfluencers always talk about taking. Our bodies make it but not enough for optimal cognitive health or high intensity training. This system is used for short bursts of very intense, explosive cardio in Zones 5-7 explained below. This energy cycle can only last 10-20 seconds before energy demands push the body above threshold.

2. The Anaerobic Glycolytic system (Lactic Acid System) primarily uses glucose for fuel, converted from carbohydrates. This system is recruited primarily in Zone 4-5 cardio, which is the realm of upper threshold speed/endurance work: assualt bike, very fast running, crossfit.

3. The Aerobic System uses mostly carbohydrates and a small percentage of fats. This is the zone most of use jog, cycle, or swim within (Zones 1-3). Because it primarily uses carbs for fuel, it has some drawbacks in terms of hunger cravings post workout. More on that below.

Image: The relative contribution of the three energy systems to the total energy supply during 90 seconds of all-out cycle exercise. Adapted from gastin 2001 [23].

Now a little more on the heath benefits of each Zone and how to intergrate them into a busy work week:

Zone 1 (50–60% of max heart rate)

This is what we call most of our 10K steps: the majority of the walking we do around the house, in the office, and without any structured intentions. It gently conditions the heart, helps reduce stress, and promotes muscle recovery without causing nervous system fatigue. It's also useful for improving insulin sensitivity in a low-impact way by drawing glucose (sugar) into our muscles to use for energy, lowering blood sugar levels, and making the body more responsive to insulin over time. It also reduces stress hormones like cortisol, which can block insulin function. I suggest clients consider combining low-focus tasks like email with a block of 30-40 minutes of steps on a small walking pad that can be stored under a couch, or walk while listening to a podcast or watching TV before bed. Another solution is getting off of the train 4-5 stops early and walking the rest of the way home. The downside is while these steps are certainly better than nothing for health health for absolute beginners or sedentary folks, they are not enough to push the walls of the heart to improve cardiac output significantly after a few months of consistency.

Zone 2 (60–70% HR)

These are the steps we take when commuting (typically walking at our fastest pace), or jogging. I’ll suggest most clients try to set the treadmill for a range of 3-4 MPH, depending on height. Zones 1 and 2 are somewhat confusingly called the "fat-burning zones" because our bodies use fat as the primary fuel source. A mix of carbs and fat are used for fuel. It is excellent for long-term weight loss, building aerobic endurance, and strengthening the heart over time. It also supports mental clarity, reduces anxiety, and helps regulate blood sugar. Most clients will have the most success finding windows of time to fit more Zone 1 and 2 cardio into their workweek.

Zone 3 (70–80% HR)

This is what most people would call mid-intensity running, swimming, and constant cycling without stopping. This is primarily moderate-intensity aerobic movement that has the most cardiovascular health benefits along with Zone 2, we’ll get into why in a moment. It also improves muscular endurance via the sprouting of additional capillaries. It burns more total calories than lower zones in a shorter duration, but tends to be harder to maintain due to impact forces on joints, sweating, and finding a solid block of time to do it. The downsides of Zones 2 and 3 is that carbs are burned as the primary fuel source because they can be metabolized faster at this mid-intensity. The result is hunger pangs that kick in shortly after the session (the body loves carbs because they are quick energy)…making it all so easy to overeat a whole bag of chips or other carb-heavy snacks. Zones 3 and above tend to require a structured block of time in our weekly calendar to complete (again….hair washing, BO, sweating etc). It’s no wonder why most of us struggle to find chunks of time throughout the week for this kind of movement. The only way I was able to fit it into a 50 hour work week when I was training for the marathon in 2015 was to leave a change of running clothes at the office and run home from work.

Zone 4 (80–90%)

This is a high-intensity threshold that trains the body to work harder before fatigue sets in: running near our max pace, hard cycling, tue HIIT workouts, or stairmaster. It improves our lactate threshold (muscle endurance), boosts cardiac output (blood flow), and significantly increases our fitness level. Mentally, it builds resilience and sharpens focus. I lean into this Zone as my structured cardio during the week because I can get a significant caloric expenditure and push my heart rate in a short period of time, usually no longer than 20-25 mins. It is also the easiest of the higher intensity zones that can be done with machines (rowing, ski ERG, stationary bike, etc).

Zone 5-7 (90–100%)

This is maximal effort used for short bursts of high-intensity activity: sprinting, full-on heavy KB swings, Olympic style lifts like cleans and snatches…basically any multi-joint movement that can’t be maintained for longer than 10-20 seconds. It trains peak speed and power, challenges the heart at its highest capacity, and produces a strong endorphin and adrenaline response. EPOC, or Excess Post-exercise Oxygen Consumption, is commonly known as the "afterburn effect". It refers to the increased metabolic rate our body maintains for hours even after we finish exercising, burning more calories than we did during the workout itself.

Now the most important aspect of what cardio means in terms of heart health. Two words…Cardiac Output.

Cardiac output (CO) — the volume of blood the heart pumps per minute — is often considered a the widest indicator of cardiovascular performance. It’s very important, but not entirely sufficient on its own: we could have a “strong” heart that pumps a lot of blood…but clogged arteries and or high blood pressure for other reasons too long to address in this post.

The formula we use for this is CO = Stroke Volume × Heart Rate. It quantifies how much blood is delivered to the body every minute. Not all forms of cardio are equally effective in terms of improving cardiac output because some forms won’t deliver the same amount of blood over the same duration of time. Circuit training classes like Barry’s Bootcamp will not improve cardiac output as much as steady-state cardio like running, cycling, or swimming, or even treadmill walking, because these forms of cardio are sustained without rest periods. A circuit training class is truncated by rest periods. Less blood is ejected from the heart during the same duration. Adequate cardiac output ensures sufficient oxygen and nutrient delivery to vital organs (brain, kidneys, muscles, etc.). Low CO leads to fatigue and organ dysfunction. This health bucket captures the effects of our heart strength (myocardial contractility), total blood volume, heart rhythm, and vascular resistance to a degree, and is what we want to strive for most while considering the respective caloric expenditure benefits of all zones.

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A weekly interactive health & fitness library.

Greetings Flux peoples. I’m heading into finals this week and will take a break from posting for the next 2 weeks until I re-emerge, so billing is paused until I return to my writing desk (paid subscribers won’t be charged until billing is turned back on). I’m currently dissecting the entire human brain in my doctorate program, so that gives you an idea of how much is on my….plate. So, enjoy this post of a mix of new and never before shared AMAs from the archives :)

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A weekly interactive health & fitness library.

If you’ve been following at least two bodybuilders on any form of social media over the last 6 months, you’ve likely seen a deluge of near aneurysm inducing evidence vs experience-based arguments about hypertrophy methodologies. The progression (or regression?) of fitness content has gone from an upslope of even-keeled, educational content, to a sharp nose dive into all out war. New clients often express that one of the most frustrating aspects of getting in shape is the lack of a universally agreed upon standard of truth. While no industry is without its medley of contrasting perspectives, weightlifting—hypertrophy in particular—is rife with seemingly endless arguments on the exact angle your shoulders (or insert any other muscle) should be positioned to bias (target) a specific muscle group. This content can seem like manna from heaven for those without much of an understanding of anatomy or kinesiology. The reality is, 1-2 inch adjustments, pronating vs supinating wrists, and training muscles at longer lengths have very little utility compared to simply hammering away at a program designed to minimize nervous system fatigue and atrophy between sessions, with a clear strategy of what cicumstances to increase weights with respect one’s own unique body morphology.

Very few people will benefit from any minor deviations away from foundational weightlifting form. This is because most people won’t get close to the threshold of the upper limit of their motor unit recruitment. A motor unit is the nerve (extension of the brain and spinal cord) and the muscle fibers it innervates (turns on). When we lift weights over years, we gradually improve our ability to recruit more motor units as we lift increasingly heavier weights, only if we’ve been truly consistent. The largest fibers are our type II muscle fibers, and they are not recruited unless we place them under significant mechanical tension in the fewest amount of reps (PMID: 32466745). The sobering reality is that few lifters will reach this threshold, as life is often messy. There is no magic ‘one cool trick’ to muscle growth. What does matter, is neuromechanical matching: the angles that dictate which muscles will become the primary movers and work the hardest. While this may sound complicated, the reality is that 90% of the most common exercises performed in the gym with the least amount of equipment or gimmicks are those that will produce a favorable, lasting adaptation. We can ignore the reels that tell us to to wrap our thumbs around the bar to “explode our lats”, or dig into your heels to magically sprout a bubble butt, so long as we efficiently utilize progressive overload ove the course of at least a few years of true consistency.

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A weekly interactive health & fitness library

This week’s practical workout guidance tackles one of the most common questions my long-term clients ask when life gets messy: “What exercises should I focus on when I can’t finish my entire workout?”. You know the story: you finally speed through a tripple header of back to back Zoom meetings, fire away a slew of schedule send emails and blast out of the office, only to get to the gym and discover everybody and their grandma hogging all the dumbells and squat racks. You now only have 37 minutes to complete your perfectly timed 1 hour lifting workout. What do you do? If you know much about exercise physiology, you know that atrophy (muscle loss) occurs 48 hours after your last lifting day. If you did chest on Monday, you’d need an exercise that would work your pectorals, triceps, and delts on Wednesday to stop the clock and give the body a reason to hold on to your hard-earned muscle tissue. Thankfully, it doesn’t take much tension to retain muscle - as little as one set taken to failure will signal the nervous system that metabolic resources are needed to maintain this tissue, and muscle protein synthesis (growth of muscle tissue) will resume for another 48 hours. The tricky part is knowing which exercises to prioritize in only 35 minutes.

Here’s a fast and easy way to narrow it down: compound exercises. These are our “meat and potato” exercises like squats, deadlifts, rows, pushups/bench presses, overhead presses, dips, and pull/chin ups. Further split second decision making is required: we may not know which of these exercise variations will stimulate the most tissue and thus stop the atrophy clock. Here’s my favorite grocery list. Choose one exercise from each category:

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