I Tried the Newest Competitor to the Apple Watch and Learned I'm Dehydrated

We independently research, test, review, and recommend the best products—learn more about our process. If you buy something through our links, we may earn a commission.

fitness tracking watches from Masimo and Apple

Verywell / Masimo / Apple

Stepping onto the treadmill, I glance down—on my wrist is the device that will hopefully not only motivate me but tell me how much progress I’m making on my often-ill-fated first-of-the-year fitness goals. But this time, it’s different. I’m testing two fitness watches that promise to change the way I look at my health data: the Apple Watch SE and the recently released Masimo W1 Advanced Health Tracking Watch.

Full disclosure—both devices were sent to me by Masimo. As Masimo, a company best known for its hospital-grade diagnostic equipment and groundbreaking pulse oximeters, enters the crowded field of fitness wearables, they are pitting its watch against a close competitor. Both devices constantly monitor heart rate, pulse rate, blood oxygen saturation rate, and more, but one is focused on performance, while the other tries to keep things easy to understand for the casual exerciser.

After a month of wearing both intermittently, I found that each device offers a revealing snapshot of your health, but their target audiences are completely different.

Apple Watch: For Motivation and Social Connection

Apple Watch SE


Buy Now: Apple Watch SE, $249 at

Until this point, my fitness trackers have been rudimentary. I was still wearing my FitBit Charge 3 prior to testing the watches. Trackers like FitBit give you the basics: steps, distance, heart rate, and sleep motion to start. The Apple Watch SE takes that idea and does what Apple does best—it makes it pretty and social.

Apple’s Activity app offers colorful visual signposts for your daily movement goals. Close your three rings, and you’ve moved sufficiently for the day. But when I was actually working out, I found that the Apple Watch lagged in updating my heart rate on the face display and required several taps to get to my metrics screen. This is not exactly convenient when sweating it out on the treadmill.

Multifunctionality is also a selling point for the Apple Watch, but I found the ability to sync the watch to my phone apps distracting, and I spent a significant amount of time taking apps off the watch. The Apple Health app did offer valuable functionality but took quite a bit of fine-tuning to equal the built-in metrics that came automatically with the Masimo W1, like the ability to take an electrocardiogram (ECG) to monitor your heart rhythm.

Masimo W1: For the Athletes

Masimo W1 Advanced Health Tracking Watch


Buy Now: Masimo W1 Advanced Health Tracking Watch, $499 at

On the other hand, or wrist, as the case may be, the Masimo W1 offers metrics galore but little in the way of social connection or gamified motivation. The watch is available in one size, which may feel bulky for those with smaller wrists, but it offers a wealth of valuable information, some of which is unavailable on any other fitness wearable.

One of those metrics that I found particularly revealing was hydration level. The W1 is the only watch on the market that accurately and continuously monitors hydration, and it quickly revealed what I knew but routinely denied: I’m chronically dehydrated. Since the measurements are continuous, it became my goal to move the needle above the hydration line, but I only made it once or twice over my testing time.

While the Apple Watch offers a bit too much connectivity and app options, the W1 goes to the opposite extreme. The W1 is a scalpel when compared to the Apple Watch’s Swiss Army knife. The data is clear-cut and easy to access anytime with just a glance at one of four face options or a click into the menu, but it lacks a colorful interface or any other health apps like trainers or fitness programs.

For a more detailed study, the Masimo Health app offers reports that can be sent to healthcare providers or family members using one of their Personal SafetyNet Service memberships. A pay-per-session health coach is also coming soon for a monthly fee.

The Masimo W1 stands out for its continuous monitoring abilities, which not only makes it easier to use in the midst of a tough workout, but allows anyone looking at reports from the watch to see trends that can lead to a more accurate diagnosis. Instead of giving snapshots of your oxygen saturation, pulse rate, respiration rate, or hydration levels, it gives you the equivalent of a documentary of your day.

How Much Fitness Wearable Is Enough?

After observing the differences, I had to ask—how much data is enough? Bradley Serwer, MD, chief medical officer and interventional cardiologist at CardioSolution in Bethesda, Maryland, says that while information is good, unless users understand what it means and how to use it, it can be overwhelming.

“If you’re actively working with an exercise physiologist, and you know what to do with this information, it can help you train smarter and safer,” Serwer told Verywell. “But you need to understand what each parameter and variable actually means.”

Serwer said that the specifics of the information provided by advanced fitness wearables can occasionally be overly concerning to those without a thorough understanding of the metrics. The Masimo W1 actually monitors both heart rate and pulse rate separately, which Serwer said is fantastic from a diagnostic standpoint. But many people don’t realize that the numbers can be different, leading some to believe that they have a heart issue.

“Some people have what’s called PVCs, premature ventricular contractions,” Serwer said. “They can occur every other normal heartbeat. So you have a normal beat followed by a premature beat.”

Since the premature beat doesn’t register on a device, patients might see heart rates in the 40s and panic, assuming they are at risk of a heart attack. If the same heartbeat was seen during a visit to the cardiologist, it could be explained easily. Serwer says that information without context can cause panic.

Advanced wearable technology also requires knowledgeable setup. Serwer said that he’s seen fit people assume that they were in atrial fibrillation after wearing their watches on the opposite wrist than the one that the factory default is set up for. Since the device doesn’t realize that it’s on the opposite wrist, it doesn’t report the electrical activity of the heart correctly.

The ability to view your hydration levels, though, is a unique and useful tool. While many athletes weigh themselves before and after an intense workout to gauge how much hydration they’ve lost, that isn’t always possible for distance runners and other athletes in the field.

The Final Verdict

While the Apple Watch may be popular, it’s aimed at a completely different demographic than the Masimo W1: those who want to connect and casually compete on daily fitness goals with friends. While the Apple Watch does offer impressive functionality and the ability to provide information to medical providers if used correctly, that doesn’t feel like its primary aim.

The Masimo W1 feels like a tool rather than a toy. Its continuous monitoring and accurate diagnostics would be a boon to elite athletes that know their bodies and need to train within a specific window of heart rate. It can also help athletes stay hydrated, which can be essential to safely competing. The W1 also has more potential for those that need continuous monitoring for health reasons. Used in conjunction with your cardiologist or other specialist, it could provide extensive information without using hospital-grade diagnostics.

As a fitness novice, the Apple Watch was more approachable for my needs, but I could see my father, who is a heart patient, getting immeasurable value out of the Masimo W1. It’s up to you to gauge how much information you need to move forward in your fitness journey.