EDITOR’S NOTE CORRECTION: If you are trying to use the special Pump Club code for NOBULL, the correct code is ARNOLDPC35OFF. Our apologies for the error. That code is good for the next 48 hours.
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Today’s Health Upgrade
Does Tylenol cause autism?
The stability question
How much you alter your bedtime matters more than you think
Health
The Relationship Between Tylenol During Pregnancy And Autism: Here's What 1.5 Million Births Found
Pregnancy is already an exercise in managing information overload: the unsolicited advice, the contradictory headlines, the well-meaning friend forwarding articles at midnight.
Recently, one fear spread particularly far. Some people believe taking acetaminophen (Tylenol) during pregnancy increases autism risk in children. For many pregnant women, that was enough to avoid the medication entirely, sometimes leaving fevers untreated or switching to alternatives with weaker safety records. New research offers some clarity.
A nationwide study tracking more than 1.5 million pregnancies found no meaningful association between acetaminophen use during pregnancy and autism in children. And one specific aspect of the study adds relevant context.
Researchers followed children born between 1997 and 2022, identifying in utero acetaminophen exposure through maternal prescription records. After adjusting for known confounders, including maternal age, health history, and other medications, the link to autism was as close to no effect as epidemiology produces.
Here's why this study is different: Researchers compared siblings born to the same mother: one pregnancy where she took acetaminophen, one where she didn't. Same parents. Same home. Same genes.
If the medication were actually driving autism risk, you'd expect to see higher rates in the exposed sibling. Researchers didn't find that.
Some studies that suggest a correlation likely reflect a simpler explanation: women who take more medication during pregnancy tend to be older and have more underlying health conditions. Those factors, not the Tylenol, were probably doing the work. When you remove that noise by comparing children within the same family, the association disappears entirely.
The study tracked prescription acetaminophen, not over-the-counter purchases. That limits what we can say about typical sporadic use, though nothing in the data suggests harm.
Untreated fevers during pregnancy carry documented developmental risks. Avoiding a medication out of misplaced fear carries consequences, too. These decisions belong with your doctor, who knows your full picture. But if this fear has been following you, this study, which had no industry funding (if you’re worried about conflict of interest), found the evidence doesn't support the connection.
Together With NOBULL
Do You Have A Stability Problem?
Picture a tough set of squats or deadlifts. One where the bar slowed halfway up, and you had to fight for it. Many variables determine whether you finish the lift. And on your most challenging reps, the little details can make a real difference. And that’s where one aspect is often overlooked.
Scientists found that your shoes influence how stable you are on some lifts, and stability is a key ingredient to preventing injuries, generating force, and helping you grind through the hardest reps.
Researchers had trained lifters perform conventional deadlifts in cushioned running shoes and barefoot. The barefoot lifters developed force significantly faster and showed less side-to-side foot sway, indicating a more stable base. A larger study on deadlifts found a similar outcome.
So while you might lace up any type of shoe, what you wear on your feet influences the activities you enjoy. Foam built to absorb impact on a run has to be compressible by definition. Under a heavy barbell, that compressibility shifts your base unevenly.
It might seem like something you don’t notice or think about, but running shoes during lifting can cause a wobble, which can cost you the lift.
This is why some people train barefoot, and why it's a defensible choice for some lifts (if you look at old photos, that’s how Arnold used to train). But most of the training week isn't barefoot-compatible — cardio, circuits, sprints, lateral work, a gym floor with plates on it. All of that wants a shoe. And most of the shoes people own were built for running, which means they are a compromise the minute you walk under a bar.
This is what training shoes are actually for. A shoe built for the full training week has to do five things at once: enough stability to hold you steady under a loaded barbell without feeling rigid, enough cushioning to absorb impact during cardio without going soft when it counts, traction that works across surfaces and directions, breathability that holds up through high-intensity sessions, and materials durable enough to survive the actual grind.
Most shoes optimize for one or two of those. The rest is a compromise.
Removing that compromise was the thinking behind the NOBULL Drive 2: a hybrid shoe engineered around a complete training week. The 4mm heel-to-toe drop gives you a flat, stable platform for lifts. Compression-molded EVA (CMEVA) foam in the midsole keeps it responsive and light. A re-engineered mesh upper stays breathable through sustained effort without losing structure.
If you’re looking for a shoe you can use for strength work, cardio, and circuits without having to change footwear between sets, we recommend the NOBULL Drive 2.
As an APC reader, you get the Drive 2 for just $99. Use code ARNOLDPC35OFF at checkout. But the special offer is only available for 48 hours.
The work you're building is real. The details that support it should be too.
On Our Radar
Why Your Bedtime Is Linked To Cardiovascular Risk
We’ve said it before, but a new 10-year study suggests that it’s time to take a hard look at when you go to sleep. Or more accurately, how consistent you are with your bedtime.
Among people sleeping less than eight hours, those with irregular bedtimes were associated with roughly double the risk of a major cardiac event compared to those who kept a consistent bedtime, while irregular wake-up times showed no significant association.
Researchers tracked adults for 10 years, measuring sleep timing using wrist-worn devices over seven consecutive nights. They focused on whether bedtime consistency, wake-up consistency, or sleep midpoint consistency predicts major cardiac events, such as heart attacks, strokes, heart failure hospitalizations, and cardiovascular death.
What separated irregular from regular sleepers wasn't dramatic. Regular bedtimes varied by about 33 minutes night to night. Irregular sleepers varied by roughly 108 minutes, the equivalent of going to bed nearly two hours later or earlier each night with no predictable pattern.
The association was only observed among participants who slept for less than about 8 hours. Among those who got more than 8 hours of sleep, no significant association was detected, though researchers caution that the low number of cardiac events in that group may have limited their ability to detect a difference, not necessarily confirming a protective effect of adequate sleep alone.
To be clear, getting enough hours and keeping a consistent schedule may both matter, but sleep consistency matters more than most people think.
Irregular sleep schedules are thought to disrupt circadian rhythm, your body's internal clock governing cortisol release, blood pressure patterns, and inflammatory markers. Shift that clock night after night, and the downstream physiological effects accumulate.
The best approach is simple: Pick a bedtime and stay within 30 minutes of it most nights.
Better Today
Take any of these tips from today’s email and put them into action:
1. A Sibling Study of 1.5 Million Births Finds No Link Between Pregnancy Tylenol and Autism
A study tracking 1.5 million pregnancies between 1997 and 2022 found no meaningful link between acetaminophen use and autism in children. Researchers compared siblings born to the same mother — one exposed to Tylenol in utero, one not — and the association earlier studies had flagged disappeared, suggesting those findings captured maternal health factors rather than the medication itself. If this fear has shaped your prenatal decisions, the evidence doesn't support it, and untreated fevers during pregnancy carry documented developmental risks of their own.
2. Why Running Shoes Destabilize a Heavy Lift: The Biomechanics Most Lifters Overlook
Trained lifters who performed conventional deadlifts barefoot developed force significantly faster and showed less lateral foot sway than when performing the same lift in cushioned running shoes. The mechanism is mechanical: foam built to compress under running impact compresses unevenly under a loaded barbell, shifting your base at precisely the moment stability matters most. Most of the training week isn't barefoot-compatible — cardio, circuits, lateral work — which is why a shoe built for lifting, not for running, is the actual requirement.
3. A 10-Year Study Found Irregular Bedtimes Doubled Cardiac Event Risk (Wake-Up Times Didn't)
In a 10-year study, adults sleeping under eight hours who kept irregular bedtimes had roughly double the risk of a major cardiac event — heart attack, stroke, heart failure hospitalization, or cardiovascular death — compared to those who went to bed at consistent times. Irregular wake-up times showed no significant association. The difference between groups was smaller than it sounds: regular sleepers varied their bedtime by about 33 minutes night to night, while irregular sleepers swung by roughly 108 minutes, which is thought to disrupt circadian regulation of cortisol, blood pressure, and inflammation. The practical target isn't perfection: pick a bedtime and stay within 30 minutes of it most nights.
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
