Can A Sleep Tracker Make Your Rest Worse?

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Today’s Health Upgrade

Health
Is Your Water Pitcher Shedding Plastic?

A filter pitcher can improve what comes out of your tap. But once the water passes through the filter, it usually sits in a plastic reservoir. 

If your pitcher is old, scratched, or filled with the same water for weeks, it could become another source of microplastic exposure.

The concern isn't cold water sitting in plastic for a day or two. Heat, time, and wear appear to have a much bigger effect on how many particles plastic releases.

A meta-analysis covering 237 measurements from 30 studies found a consistent pattern: warmer temperatures caused plastic containers to shed more particles. This is why keeping hot food and drinks away from plastic remains one of the simplest ways to reduce exposure. Cold storage generally produced lower levels.

The research on refrigeration itself is mixed. In one 2025 lab study, water stored for 30 days in a plastic takeout-style container picked up about 45 percent more particles in the fridge than at room temperature. The researchers proposed that cold temperatures caused the plastic to contract and become stressed. Yet plastic bags in the same study released far fewer particles when refrigerated. 

An earlier study testing food containers found that room-temperature storage released more particles than refrigeration across every product examined.

Cold water in plastic appears to release relatively few particles, but the type and condition of the plastic matter.

Time matters, too. That same food-container study found that months of storage, even in the fridge, still released large numbers of particles. And a 2026 study of reusable bottles found that water sitting inside a bottle released a substantial number of particles even without squeezing, shaking, or scrubbing. Everyday wear can add to that release.

Here's how to improve the habit without overthinking it:

One more small adjustment: don't repeatedly freeze and thaw water in plastic bottles. A bottled-water study found that the process increased nanoplastic release.

Microplastics have been detected in human blood, including in 17 of 22 healthy donors in a 2022 study. Scientists still don't know what levels cause harm, if any. 

There's no reason to panic about microplastics. But if you can reduce your exposure through simple methods — whether not microwaving food in plastic containers, cooking on better cookware, or getting a better pitcher — you can feel confident you’re doing what you can to protect your health and cut back on potential added risk. 

Together with Rorra
The Best Water Filter Is The One You'll Actually Use

Here's something we say about training all the time, and it's just as true for water: the best option isn't the one with the best specs on paper. It's the one that fits your life well enough that you actually stick with it.

For years, water filtration had a gap. The easy option (the pitcher in the fridge) mostly fixed taste and stopped. The options that handled the health tier (lead, PFAS, microplastics) meant a countertop system or a plumber.

So most people chose the easy option and assumed their water was handled. It wasn't.

Rorra just closed that gap. The new Filtered Pitcher puts the same Enfinity™ nanofiber filtration from the Countertop System into a 13-cup pitcher that fits in your fridge. 

It's independently lab-tested to target PFAS, lead, microplastics, and 50+ other contaminants, and it's NSF-tested to NSF/ANSI 42, 53, and 401. That's the health tier, in the format everyone already knows how to use.

Remember the "removes 99%" line from last time? On this one, the 99% is PFAS and lead.

No install. No counter space. No plumbing. Fill it, and you get the water you thought your old pitcher was giving you.

It's lab-grade borosilicate glass and medical-grade stainless steel, one filter lasts about 200 gallons (roughly three months), and it's backed by a money-back guarantee.

If you've been putting off a real filter because the real ones felt like a project, start here. It's the most accessible way to do this right.

Pump Club readers get 15% off the Rorra Filtered Pitcher. No code needed. Click this link and the discount is automatically applied.

Not ready to buy? Start where everyone should. Test and see what's in your water first. No purchase required.

Clean water isn't about the perfect setup. It's about the glass you actually drink from every day.

Fact Or Fiction
Did a New Study Just Prove Carbs Don't Build Muscle?

I've always heard you have to eat big to get big. Now I'm seeing headlines that a new study found extra carbs don't build muscle. So which is it? -Marcus

The new study brings up some interesting questions. The way it's getting retold offers misleading answers. 

Carbs can help fuel hard training, especially long, high-volume sessions, and eating enough supports muscle growth. But a traditional bulking approach (where you eat hundreds or thousands of additional calories) might not only be unnecessary; it could easily lead to too much unnecessary weight gain. 

In the latest study, researchers analyzed people with nearly 10 years of lifting experience and made a small dietary adjustment. For one 8-week period, they consumed a daily protein shake after a workout. And then, in a separate 8-week phase, they gave them the same protein shake but this time with about 50 grams of added carbs. Otherwise, they kept their usual training and eating habits.

Muscle and strength changes weren't meaningfully different either way. That's what's getting reported. But there's more to the story.

First, the carb phase was not "eating big." The shake added 50 grams of carbs, but food logs showed only about 33 extra grams a day, possibly because people ate a little less elsewhere. That's roughly one large banana. The logs did show a larger calorie gap, but those numbers didn't fully add up, so the real difference is hard to pin down.

In other words, adding more carbs immediately after a workout didn’t seem to increase jumpstart additional muscle gain.

But here's what's probably a bigger reason no difference showed up, and why it can help you avoid jumping to premature conclusions about what is or isn’t working.

After many years of training, muscle growth happens slowly, and eight weeks is a blink. 

While many programs promise 4- or 8-week transformations, the changes you seek usually come from more consistency and commitment.

If you're a beginner or haven't exercised in a while, you can definitely build muscle and drop fat faster. But if you've been training for many years, like the people in the study, realistic gains might be just a few pounds of new muscle a year, at best.

It's also worth mentioning something else that is being overlooked.

While many people assume carbs make you fat, the extra carbs didn't cause more fat gain. 

Both phases added about a pound of fat or less, and the gap between them was too small to matter. 

The bigger picture: carbs and protein both help support muscle growth. Carbs can help you push harder during your workouts. Protein can help with recovery. Extra calories can help you maximize muscle growth, but training drives most of that process, so you don’t need to flood your body with tons of extra calories. 

A slower increase is likely your best bet. And if you don’t want to calculate macros or think, and just want to know what to eat, this can help.

Recovery
The Sleep Problem Your Tracker Might Be Feeding

A sleep score can change your morning before the day begins. You felt fine, but the app gave you a 48. Now an imperfect estimate has become a problem to solve.

If your sleep tracker is telling you how to feel or act, or setting expectations of what you can accomplish on bad sleep, you might not be using the data in a way that helps you.

Sleep researchers call this orthosomnia: becoming so focused on improving sleep data that the tracking itself makes sleep harder. The term came from a paper about three patients being treated for insomnia whose devotion to their devices interfered with treatment.

Researchers recently surveyed more than 1,000 adults and nearly half had used a sleep app or wearable, usually a smartwatch. Many users said sleep trackers help, but some say they backfire.

Roughly 1 in 7 users said tracking improved their sleep, while about 1 in 6 said it made them more worried about sleep.

Trackers are not inherently bad, and the device doesn't need to ruin your sleep to cause trouble. It only needs to give you one more reason to worry.

Younger users reported the most benefits and the most worry, while people with less education reported slightly more negative effects.

The problem starts when people treat an estimate like a diagnosis. Consumer trackers use movement and heart rate to guess when you're asleep and how much time you spend in each stage. They don't measure brain waves the way a clinical sleep study does.

A night that felt perfectly normal can receive a poor score, and someone prone to perfectionism may start changing routines, spending more time in bed, or worrying about hitting the right numbers.

The early evidence suggests the device may be only part of the story. In another study, orthosomnia scores were most closely linked to unhelpful beliefs about sleep and obsessive-compulsive tendencies, and also tracked with perfectionism and health anxiety.

That suggests the problem may be rooted more in how people think about sleep than in the device itself.

These studies were self-reported and captured one moment in time, so they can't prove that trackers caused the worry or poor sleep, or tell us which came first.

If you’re unsure if tracking devices are right for you, start by asking: Is the data helping you make better decisions, or is it simply giving you more to manage?

If your tracker is becoming another source of stress:

Adam’s Corner
Put It To Bed

A note from AB: I thought about responding to some “fan mail” I got last week, which kindly requested the following:

Any chance y'all can put Adam's Corner to bed? It's just random nonsense every week and trying so hard, so, SO hard to sound insightful. -Mike

Well, Mike. Good news. You get your wish this week. I’m shooting videos all week with our incredible Pump Club app team (and some members), and I didn’t have time for new random nonsense. 

But that got me thinking: is there anything you want me to cover here?

My columns are different from the other items in the newsletter. And, with the exception of Arnold’s Monday Motivation, it’s a place with no rules and an opportunity to explore a wide variety of topics. 

I’ve thought about sharing interviews, experiments, journal entries, predictions, and other observations on a wide variety of topics, all focused on helping you become better every day. 

So, this week, you get to play editor.

If you have a suggestion, request, or even critical feedback, please hit reply and let me know about it. All recommendations are welcome. -AB

-Adam Bornstein is the co-founder and co-editor-in-chief of Arnold’s Pump Club

The Positive Corner of The Internet
About Arnold’s Pump Club Editorial Standards

We do things a bit differently here, starting with transparency.

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Publisher: Arnold Schwarzenegger​

Editors-in-chief: Adam Bornstein and Daniel Ketchell