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Today’s Health Upgrade
Cardio that burns fat and maintains muscle?
Time to check your cookware receipts
A hidden reason why you keep getting hurt
Adam’s Corner: Forgetting, calorie counting, and the science of change
On Our Radar
Your Cardio Burns Fat. But Does It Keep Your Muscle?
Most people treat cardio like a simple math problem: more movement, more calories burned, better outcome. And for a lot of goals, that logic mostly holds. But new research on older adults points to a wrinkle worth knowing: what you burn and what you keep might depend heavily on how hard you're working.
A preliminary study found that both high-intensity interval training and moderate-intensity cardio reduced fat mass, but only HIIT preserved lean muscle, while moderate-intensity cardio led to modest muscle losses alongside the fat.
Researchers randomly place healthy adults into one of three 6-month treadmill programs: low-intensity training, moderate-intensity continuous training, or high-intensity interval training. All sessions ran for 45 minutes, three times per week, under close supervision. The HIIT protocol alternated hard intervals at 85% to 95% of max heart rate with short active recovery periods. Adherence was exceptional, with nearly 100% of participants completing the study across all groups.
Both HIIT and moderate-intensity cardio improved visceral fat, the deeper abdominal fat tied to metabolic risk. But only the HIIT group maintained lean muscle mass.
The moderate-intensity group shed modest amounts of muscle alongside the fat. Low-intensity training results were harder to interpret cleanly.
The scientists believe high-intensity work places greater metabolic stress on muscle, sending a stronger signal to preserve it during a fat-loss response, essentially telling the body to burn fat rather than eat muscle tissue. Moderate cardio may not generate enough of that signal to trigger the same protection.
The study wasn't statistically powered to confirm these differences. In other words, it’s a meaningful signal but far from a settled verdict.
If you're already doing steady-state cardio, nothing here suggests stopping. It’s good for many reasons, including heart health and overall fitness. If fat loss feels stalled, or you’re worried about losing muscle mass, you could swap out one or two slower cardio sessions for interval work that alternates between harder and easier efforts for 20 to 30 minutes.
The older you get, the more muscle preservation matters. That doesn’t mean you have to sprint like you were 20. But it does mean you have to bring more intensity (relative to your ability) because it’s one lever you control.
Together With Our Place
Where Did You Buy Your Cookware? It Matters More Than You Might Think
Most people who switched to "healthier" cookware made that decision based on material: ceramic instead of Teflon, non-stick instead of aluminum. That instinct is reasonable. But a growing body of peer-reviewed research suggests the more important variable isn't what your pan is made of. It's where it came from.
A peer-reviewed study found that aluminum and brass cookware sold on Amazon, Etsy, and eBay contained high lead levels that readily migrated into acidic foods, while stainless steel from the same marketplaces tested significantly lower.
Researchers analyzed 51 pieces of cookware purchased from U.S. online marketplaces between 2021 and 2023. Using a precise method for detecting trace metals, they found that imported aluminum and brass cookware leached substantial amounts of lead into acidic solutions designed to simulate real cooking conditions. Stainless steel purchased from those same sellers consistently performed better.
A separate market screening of more than 5,000 consumer products across 25 countries found lead concentrations ranging from 100 to 10,000 parts per million in aluminum cookware, concentrations the FDA later cited when it issued an import alert after investigators linked imported aluminum pots to elevated blood lead levels in children.
The risk is a mix of material meets food science. Acidic foods — think tomatoes, citrus, vinegar — can accelerate metal release from reactive surfaces. Aluminum and brass are reactive metals, and at low pH, that reaction speeds up meaningfully. Other materials don’t have the same reaction. Titanium, for example, acts like a shield, preventing reactions with food, even at low pH. And ceramic is non-reactive (like glass), so it doesn’t react with acidic foods.
A few practical adjustments can help keep you safe. Avoid cheap, unbranded aluminum or brass cookware from online marketplaces. When cooking anything acidic, favor titanium, ceramic, or stainless steel. And if your non-stick pan shows visible scratches or wear, replace it. A compromised coating can expose the base metal underneath.
The brand that checks every box on that list is Our Place. We've been fans of their cookware for a while because they approach the category the way this research demands: direct-to-consumer sourcing (not an unbranded import from an online marketplace), transparent materials, and a product line built around non-reactive surfaces the science points toward. When a million people make the switch to the same brand, that's not marketing. That's a signal worth paying attention to.
Our personal favorite is the Our Place Titanium Cookware Set. It’s nonstick cookware with zero coating, which means zero forever chemicals and a surface that doesn’t degrade. Instead of relying on coatings that break down, it’s made from pure titanium, ultra-hardened for lifelong durability. It combines the best of stainless steel, cast iron, and nonstick.
Our Place is running its biggest sale of the season right now, up to 40% off sitewide through April 12th. We love their stuff and bought the pans before asking them to become an APC partner.
And if you're not sure it's right for your kitchen, their 100-day risk-free trial, free shipping, and free returns mean there's no downside to finding out.
Your cookware is a daily decision. Make it once, make it well.
Fitness
The Running Risk That Has Nothing to Do With Your Mileage
Most runners who get hurt immediately audit the same suspects: too many miles, not enough rest days, worn-out shoes. Those things matter. But new research points to a risk factor that most training plans never think to address.
A study of recreational runners found that those with consistently poor sleep — shorter duration, lower quality, and more frequent sleep problems — were associated with significantly higher injury rates than runners who slept well.
Researchers sorted recreational runners into four sleep profiles, such as Steady Sleepers (average duration, above-average quality) and Poor Sleepers (shorter sleep, lower quality, more problems throughout). After controlling for age, gender, BMI, and running experience, the researchers compared injury rates across each profile.
Poor Sleepers had a 68% probability of reporting at least one injury in the prior year, compared to 55% for Steady Sleepers.
For context, 60% of all runners in the study reported at least one injury over the prior year, a reminder that injury risk in recreational running starts high.
The study wasn’t exactly perfect. It was survey-based, cross-sectional data, which means it can't confirm whether poor sleep contributes to injury or whether injury disrupts sleep. Both are plausible. What gives the findings more weight is a prior meta-analysis showing that chronic sleep shortage was associated with roughly a 58% higher injury rate, a figure that closely aligns with this study's results.
Nearly 4 in 10 runners in this study fell into the Poor Sleeper category, a larger group than you might expect. Improving sleep isn't complicated on paper: a consistent bedtime, limiting afternoon caffeine, and actually protecting 7 to 9 hours instead of treating them as negotiable.
If you're logging miles but regularly shortchanging your sleep, that may be the most important variable in your training you haven't fixed yet.
Adam’s Corner
What If You Forgot Everything You Know About Health?
He said it the way he says most things. Directly, without ceremony, as if it were obvious.
“I never did any of these things.”
I was talking with Arnold about health trends. The ones that cycle through every few years, wearing new names. Arnold has seen enough of them to know which ones disappear and which ones stick. So I asked him: after sixty years of training, what has actually lasted?
He gave me the answer, and I realized I already knew it.
The basics. It’s always the basics that work best.
And yet.
Look Into This Light
There’s a thought experiment I’ve been sitting with. Imagine someone wipes your memory clean — full Neuralyzer, Men in Black style — and you have to rediscover everything you know about health from scratch.
How long before you figure out that fruits and vegetables are good for you? That too much fast food has consequences? That exercise is the foundation of health? That sleep is non-negotiable? That stress, left unmanaged, quietly destroys you? That the people in your life matter more than almost anything you can put in a pill?
I’d guess most of us could reconstruct that list in under a week. Maybe less.
So why are we so far from that list in practice?
Part of the equation is the struggle to do what we know is good for us.
But something else is happening, too.
We have more health information available to us than any generation in history. More science, more nutrition apps, more fitness platforms, more supplements, more protocols, more content about longevity than anyone who came before us.
And yet, by some measures, we are not the healthiest generation in history. And depending on what we’re judging, not by a wide margin.
The gap between what we emphasize and what gets results appears to be growing. And I’m starting to think the “knowledge” itself is part of the problem.
Any time I open social media, I see a new video that twists science so far from reality, yet sounds so convincing. Just this morning, I saw a video suggesting that going from 10 pushups to 50 would not build strength and muscle.
I want to scratch my head, but it’s the norm. The video went into detail about actin and myosin. Things that most people won’t understand enough to question. Because it sounds smart, it’s hard to challenge, and many accept it as fact.
So we add that “truth” to what we know and stop progressing pushups the same way. And that’s just one piece of the broken puzzle. That seemingly harmless piece of information affects your behavior and prompts you to search for more nuggets like it.
The curse of information is that we’ve confused knowing more with doing better.
It’s part of the reason we write these emails every day. To simplify the noise. To help you focus on what matters. To bring to light the simple daily changes you can make, rather than stressing overcomplicated messages.
The science is starting to confirm what most people quietly sense.
When we’re given too many choices, too much complication, too much nuance, we’re less likely to act on any of them and less satisfied when we do.
When a health plan contains too many decisions — which supplement? which protocol? which meal timing window? — every micro-choice draws from the same limited cognitive well. You deplete that resource before you ever get to execution.
I don’t care about sounding smart. I care about helping you live better.
And when people pursue too many health goals simultaneously, they don’t just fall short. Research shows they experience measurable declines in well-being and adherence. The goals fight each other. Nothing wins.
This is the part we don’t want to say out loud: complexity is its own form of quitting. It just disguises itself as effort.
It’s why Pump Club app members are shocked when they join.
Our approach is different. Almost to the point that people say,
“Are you kidding me? This is what you want me to do? Eat carbs? Train three times per week? Not count calories? I’ve been doing this for 20 years, that won’t work.”
We ask them to try. To trust. To finish the foundation and be consistent. Because they have everything to gain. And if it doesn’t work, then leave. But we know something.
The basics are ignored. And they work. So when people give it a try, responses are the same.
How are my results so impressive? And why wasn’t I doing this sooner?
The Man Who Never Counted a Calorie
Think about what Arnold actually did. Not just what he said. What he did for sixty years.
He trained hard and consistently. He ate enough protein. He consumed more when he wanted to gain and less when he was cutting. He slept. He had a vision and chased it with everything he had.
Some people will mention the steroids. And Arnold has stated clearly that he doesn’t recommend it to others because of the potential risks.
But in a sport where everyone uses them, there’s a reason Arnold built the greatest physique in bodybuilding history and has maintained his health for decades.
He worked his way there, with a simplicity that would bore most people scrolling their fitness apps today.
No calorie counting. No time-under-tension calculations. No 17-step optimization protocols. Arnold has been pushing movement, intensity, recovery, healthy diet, and human connection for 50 years.
Now, that doesn’t mean nothing else matters. But there’s a difference between refinements that help and refinements that replace the thing itself.
When you spend more time reading about whether you should do 3 sets of 8 or 4 sets of 6 than you spend actually lifting, you’ve already made the wrong choice.
When you’re debating the merits of a detox cleanse versus a cold plunge for dopamine, but you never go outside, listen to good music, or call your friends, you’re missing out on the free, painless dopamine.
If you are spending hundreds of dollars on supplements but can’t remember when you last drank some water and went to bed at midnight, you’re focusing on the wrong fix.
When someone asks me whether they should try keto, carb cycling, or fasting, and then mentions that they don’t prioritize protein and fiber, rarely cook meals, and “take the weekends off” to eat and drink more than usual, I want to hand them a Neuralyzer and start over.
This is why we think carefully about what we talk about in this newsletter.
We focus on what the evidence actually shows, and it shows that you almost certainly have bigger fish to fry.
We talk about protein because it’s foundational. But we won’t overthink or overstress the type of protein you need to eat, because science says there are benefits to plant-based and animal-based sources. We won’t stress the timing, because how much protein you eat in a day matters far more than when you eat it. And we won’t create a false equivalency between powders and whole foods. Both have a place, but we only recommend supplements to supplement your diet.
We talk about fiber because most people get half of what they need, and it has downstream effects on everything. From heart health to diabetes risk, gut health to cancer prevention, fiber is one of those “magic pill” foods that people ignore because — well — it’s fiber. So eat your berries, oatmeal, whole grains, nuts, beans, lentils, seeds, avocado, or even popcorn. And if those are still a struggle, we created Fiber+ because we all need to hit our fiber minimums, and a little support is never a bad thing when you’re building a helpful habit.
We’ll talk about sleep, stress, and getting bloodwork done so you know what’s actually happening in your body, not what you’re guessing at.
These aren’t exciting. They don’t trend. They don’t have dramatic before-and-afters attached to them. They just work.
The honest, uncomfortable truth: most people don’t need more information or complicated nuance. They need fewer decisions and more action.
They need a short list they’ll actually follow, not a comprehensive plan they’ll abandon when times get chaotic (which they always do). They need the next small win, not the optimal framework.
Because what the research on long-term adherence keeps showing is an undeniable truth: consistency doesn’t come from sophistication. It comes from early success with something simple.
That first win builds belief. Belief builds habit. Habit builds everything else.
You can’t optimize your way into starting. You have to start your way into the behaviors that matter and are optimal for you.
The trendiest protocol in the world doesn’t work if you quit it in three weeks. The most basic protocol works great if you do it for three years.
Arnold knew this. He still does. Sixty years later, the principles that built the greatest physique in bodybuilding history haven’t changed. Sleep. Train hard. Eat enough of the right things. Recover. Repeat.
The trends came and went. The basics stayed.
So before you search for the next thing to add, try asking what you need to forget that has filled your mind with nonsense and complication.
Not because simplicity is giving up. But because simplicity is the mechanism that actually creates change.
The basics aren’t where you start before you get sophisticated. They’re where the sophisticated people quietly live. -AB
Better Today
Take any of these tips from today’s email and put them into action:
1. HIIT Preserved Lean Muscle in a 6-Month Study. Moderate Cardio Didn't.
A 6-month study of older adults found that HIIT — alternating intervals at 85–95% of max heart rate with active recovery — preserved lean muscle while reducing visceral fat, while moderate-intensity continuous cardio reduced fat but produced modest muscle loss alongside it. Researchers attribute the difference to metabolic signaling: high-intensity work appears to generate a strong enough stress response to tell the body to protect muscle tissue during fat loss, a signal that moderate cardio doesn't reach. If you're logging steady-state sessions and muscle retention matters to you, replacing one or two with 20–30 minutes of interval work — harder effort, shorter recovery, repeat — is the lever the data supports pulling.
2. Researchers Tested 51 Cookware Pieces From Amazon, Etsy, and eBay. Aluminum and Brass Leached Lead Into Food.
A peer-reviewed analysis of 51 cookware pieces found that aluminum and brass cookware leached substantial lead into acidic food simulations, while stainless steel from the same sellers tested significantly lower. A separate screening of more than 5,000 consumer products across 25 countries found lead concentrations ranging from 100 to 10,000 parts per million in aluminum cookware, a finding serious enough to trigger an FDA import alert. The mechanism is straightforward: acidic foods accelerate metal release from reactive surfaces, and both aluminum and brass are reactive at low pH — titanium and ceramic are not, which means they don't participate in that exchange regardless of what you're cooking. If your cookware came from an unbranded online marketplace listing, the material on the label is less relevant than the source behind it.
3. The Injury Risk Factor in 4 Out of 10 Runners That Has Nothing to Do With Miles or Shoes
A study of recreational runners sorted into four sleep profiles found that Poor Sleepers — characterized by shorter duration, lower quality, and more frequent sleep problems — had a 68% probability of reporting at least one injury in the prior year, compared to 55% for Steady Sleepers. Overall, nearly 4 in 10 runners in the study fell into the high-risk Poor Sleeper category. The finding aligns closely with a prior meta-analysis showing that chronic sleep shortage is associated with approximately a 58% higher injury rate among athletes. A consistent bedtime, limiting afternoon caffeine, and getting 7 to 9 hours of sleep may be the most impactful interventions available to any runner who has already optimized mileage, footwear, and rest days.
4. The Fitness Industry Profits From Complexity. The Research Shows Simplicity Wins.
Research on cognitive depletion and goal pursuit shows that chasing multiple health objectives simultaneously leads to measurable declines in both well-being and adherence. The cause is decision fatigue. Each micro-choice within a complex health plan draws on a limited cognitive resource before execution can begin. Arnold Schwarzenegger's 60-year approach — consistent training, adequate protein, sleep, recovery, repeat — works not because it lacks sophistication, but because it preserves that cognitive resource for the only thing that creates results: showing up. The most important optimization most people can make isn't adding a new protocol; it's eliminating the complexity that's preventing them from executing the foundation they already know works.
The Positive Corner of The Internet
About Arnold’s Pump Club Editorial Standards
We do things a bit differently here, starting with transparency.
The Content: All APC emails are researched, written, and fact-checked by the APC editors (see bottom of the email), with written contributions from Arnold (noted with “Arnold’s Corner”). Links take you to original studies (not second-hand sources).
Does AI play a role? Not for the primary content, but it is used in two ways. The main items are original content written by the APC team. The summaries at the end are AI-generated based on the human-written content above. We also use an AI tool to review our interpretations of the research and ensure scientific accuracy. We don’t assume AI is right, but we use technology to hold ourselves accountable.
Yes, we have partners (all clearly noted). Why? Because it allows us to keep the APC emails free. We first test products, and then reach out to potential partners who offer ways to help you improve every day. The bar is set high, and to date, we have turned down millions in ad deals. (Example: we will not partner with any non-certified supplements or those without evidence in human trials). If we won’t buy the product, we won’t recommend it to you. And if there’s no evidence it works, then there’s no place for it here.
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Publisher: Arnold Schwarzenegger
Editors-in-chief: Adam Bornstein and Daniel Ketchell
