If I told you that NASA has developed a radical new way of monitoring and quantifying your workouts, and that that method outperforms all others, you’d probably assume that it involves bleeding-edge science. There would be AI, and some sort of wearable or perhaps even injectable technology. It would be very expensive.

But you’d be wrong, for reasons that tell us something important about the quest to transform training optimization from an art into a science. A new study by Mattia D’Alleva and his colleagues at the University of Udine compares different ways of assessing the “training load” of different workouts—and finds that a low-tech NASA questionnaire produces the most accurate results. The findings offer a reminder that outsourcing our training decisions to wearable tech algorithms doesn’t always outperform simply listening to our bodies. The research also raises a tricky question: is the workout that makes you most tired also the one that increases your fitness the most?

Why Does Training Load Matter?

The goal of training is to impose a stress—a training load—on your body that makes it tired in the short term but triggers adaptations that make it fitter in the long term. Going all-out in one workout isn’t constructive, even though it imposes a huge training load, because it leaves you too tired to train effectively the next day. The art of training is figuring out what mix of easy, medium, and hard workouts will enable you to accumulate the greatest possible training load over weeks and months without getting crippled by fatigue.

In its simplest form (as I discussed here), the training load of a workout is a combination of how hard you push and how long you push for. But the details get tricky. What’s the best measure for how hard you’re pushing? You could use pace, power, heart rate, heart rate variability, lactate levels, perceived effort, or other progressively more esoteric metrics. And how do you combine effort with duration? You can’t just multiply them together, because effort is nonlinear: running twice as fast for half the distance won’t produce the same training effect.

The new study, which is published in the International Journal of Sports Physiology and Performance, compares seven different ways of calculating training load. Four of them are variations on a concept known as TRIMP, which is short for “training impulse” and is based on heart rate measurements, using equations that account for lactate levels, breathing thresholds, and other details. A fifth uses heart-rate variability, and a sixth uses a subjective rating of effort. (Most fitness wearables, by the way, likely use a combination of the above methods, though their exact algorithms are typically proprietary.) The seventh method is the NASA questionnaire, which we’ll come back to.

The gold standard against which all these methods were compared is the “acute performance decrement,” or APD. Basically, you do an all-out time trial, then you do your workout, then you do another all-out time trial. Your APD is how much slower the second time-trial is compared to the first one, as a measure of how much the workout took out of you. Obviously this isn’t a practical way of monitoring training, because you can’t race before and after every workout. But for researchers, it’s a way of checking whether various methods—including the seven they tested in this study— correspond to the reality of how hard a workout is on your body. At the end, they were able to figure out which method was the most reliable predictor of training load.

What the New Study Found

D’Alleva and his colleagues recruited 12 well-trained runners (10 men and 2 women) to test four different running workouts on different days:

• Low-intensity training (LIT): 60 minutes at a pre-determined comfortable pace
• Medium intensity (MIT): 2 x 12:00 at a moderate pace with 4:00 easy recovery
• Long high-intensity (HITlong): 5 x 3:00 hard with 2:00 recovery
• Short high-intensity (HITshort): two sets of 11 x 30 seconds hard, 30 seconds easy

The performance test was running at VO2 max pace until exhaustion. When they were fresh, the runners lasted just under six minutes on average. After the one-hour easy run, their APD was 20.7 percent, meaning they gave up 20.7 percent earlier in the post-workout VO2 max run. After the medium-intensity run, the APD was 30.6 percent; after the long intervals, it was 35.9 percent; after the short intervals, it was 29.8 percent.

So how well were each of the seven training load calculations able to predict this APD? The short answer is: not very well. Here’s a comparison of APD (on the left) and one of the parameters studied, which is called bTRIMP and is based on heart-rate measurements and lactate curves:

In fact, the relationships are completely reversed: the easiest workout according to bTRIMP produces the biggest APD in reality, and the workout ranked hardest by bTRIMP produces the smallest APD. All except two of the training load calculations the researchers measured have similar upside-down relationships. The two exceptions are heart-rate variability and the NASA questionnaire, which look like this:

The heart-rate variability measures, on the left, don’t tell us much, because they’re basically the same after each of the four workouts. (You can see some subtle differences, but they’re not statistically significant.) The NASA questionnaire, on the other hand, bears a striking resemblance to the APD data, and the statistical analysis confirms that it’s a good predictor. In other words, it’s the only one of the seven calculations tested that, according to this study, accurately reflects how exhausted you are after a workout.

So what is this questionnaire? It’s called the NASA Task Load Index, or NASA-TLX, and was developed in the 1980s. It’s simply a set of six questions that ask you to rate the mental demand, physical demand, temporal demand (how rushed were you?), performance (how well did you do?), effort, and frustration of a task. You answer each of these questions on a scale of 1 to 100, then the six scores are averaged—and presto, you have a better measure of how hard your workout was than your watch or heart-rate monitor can provide.

What the NASA Questionnaire Misses

These results don’t mean that we should all start recording NASA-TLX scores in our training logs. Questions like how hurried you felt don’t seem very relevant to running, or to training in general. What’s more significant about the questionnaire is what it doesn’t include: any measure of how long the workout was.

All the other training load measures rely on a combination of intensity and duration. But the effect of duration swamps the measurement: that’s why the bTRIMP graph above shows the 60-minute easy run (LIT) as the workout with the biggest training load. It’s really just telling us that it was the longest workout. The NASA-TLX, on the other hand, just asks (in various ways) how hard the workout felt once it was done. That turns out to be a better way of predicting how much slower you’ll be after the workout.

There’s an implicit assumption in all of this discussion, though, which is that the workout that provides the biggest training load is the one that will improve your fitness the most. Is APD—how much slower you get over the course of a single workout—really the best predictor of fitness gains? It’s easy to come up with scenarios where that’s not true. If I sprain my ankle, my APD will be enormous, but that doesn’t mean I’m going to be an Olympic champion next month. Similarly, you can imagine workouts that would inflict a disproportionate amount of performance-sapping fatigue—steep downhill running, for example—compared to their fitness benefits.

Perhaps what we’re seeing here is not so much “good” (NASA-TLX) and “bad” (TRIMP) measures of training load, but rather good measurements for two different types of training load. The APD and NASA-TLX mostly reflect how hard/intense/fast the workout was. TRIMPs and other metrics that incorporate duration end up mostly reflecting how long the workout was. There’s no reason to assume that these two parameters are interchangeable. It’s not just that you can’t get the same training benefit by going twice as fast for half as long. It’s that there’s no equation that makes fast running produce the same benefits as slow running. They’re two different physiological stimuli, and the smart money says you need both to maximize your performance.

So where does this leave us? I’m not anti-data, and I’m open to the idea that some of the newer metrics provided by wearable tech might reveal useful patterns if you collect them consistently. But if you strip training down to its bare essentials, these results suggest to me that there are two separate parameters that really matter: how long and how hard. And for now, I’m not convinced that we have any measuring tools that are significantly better than a stopwatch and an honest answer to the question “How did that feel?”

For more Sweat Science, join me on Threads and Facebook, sign up for the email newsletter, and check out my new book The Explorer’s Gene: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map.

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SAN JOSE — Life Time, a company that describes itself as an “athletic country club,” has signed a lease for a site occupied by Best Buy at Santana Row in San Jose, saying it hopes to open more Bay Area locations.

Life Time leased a building at the southeast corner of Stevens Creek Boulevard and South Winchester Boulevard for its fitness- and health-oriented country club, according to documents filed on May 28 with the Santa Clara County Recorder’s Office.

“Santana Row is a great location,” said Meghan Akradi, a vice president of real estate with Life Time. “It’s hard to do better than Santana Row in terms of iconic properties.”

The building at 3090 Stevens Creek Blvd. is 60,000 square feet and is two stories, according to commercial real estate database Property Shark. The initial term of the lease is 15 years, Santa Clara County property documents show.

“This is a market where we’ve wanted to be for many years,” Akradi said. “We hope to open our San Jose location during the first half of 2027. It depends on how quickly we can get permits.”

The only Bay Area location for Life Time currently is in downtown Walnut Creek at 1315 Broadway Plaza.

The future San Jose location is expected to feature an array of amenities, according to Life Time.

“We will have great fitness areas, fitness studios, personal training sites, yoga, pilates, cafe, work lounges, a sauna, and hot tubs,” Akradi said. “We will have a kids’ academy.”

Minnesota-based Life Time takes a different approach to fitness than is the case with typical health clubs in the country, according to company executives.

“Members are calling us a country club without the golf,” said Natalie Bushaw, a spokesperson for Life Time.

In March, Fast Company placed Life Time at No. 23 on its list of the 50 most innovative companies of 2025.

“It goes much further than a typical gym,” Bushaw said. “Life Time takes a holistic approach to health, wellness, recovery and fitness. People can literally spend all day at Life Time, and they do.”

Life Time operates at least 175 athletic country clubs that have an average size of 100,000 square feet, according to the company’s website.

“It’s like a Four Seasons resort every time you walk into one of our country clubs,” Akradi said.

The company has 1.4 million members and 41,000 employees. Life Time also has at least 150 kids’ academy locations.

Life Time executives believe the company’s approach can capitalize on post-pandemic attitudes to staying healthy.

“Our company has come back stronger than ever,” Akradi said. “We are exceeding our pre-COVID member engagement, member satisfaction and member attention.”

Over the one-year period that ended in March, Life Time posted a profit of $207.5 million, an increase of 182.3%, or nearly triple the profits over the similar 12-month period the year before.

Revenue over the year-long period ending in March totaled $2.73 billion, an increase of 18.6% from the same period the prior year, according to Finance Charts.

“People are clearly emphasizing their health and wellness,” Akradi said. “We feel well positioned to continue to serve those people.”

Originally Published: June 5, 2025 at 5:30 AM PDT

Consumers today expect broadcast content to be available whenever, and wherever they want. Broadcasters are under increasing pressure to create and disseminate content in real-time and on-demand across an ever-growing number of platforms and formats. If they don’t, their competitors will.

In this environment, downtime is not an option, and reliable broadcast operations are a must. This article will explore the impact of broadcast outages and the resulting downtime and explain what to look for in a technology partner to prevent it. 

The Apple Watch is pretty accurate — at least for certain metrics.

A new University of Mississippi meta-analysis of 56 studies finds the Apple Watch delivers fairly accurate data for heart rate and step counts — but shows a much wider margin of error when it comes to calories burned.

In the year 2025, wearable tech is almost startlingly common. If you walk into any gym in the United States, chances are you’re going to see wrists adorned with some kind of fitness tracker or smartwatch.

And it makes sense, too. Whether you’re concerned about your health or just looking to dial in your workouts, wearing an Apple Watch — or any other fitness tracker — seems like an ideal way to do it.

But that begs the question — just how accurate are health trackers like the Apple Watch? That’s the exact question that University of Mississippi researchers set out to answer.

The Apple Watch knows how much you move, not how much you burn

The Ole Miss study analyzed data from 56 studies comparing the Apple Watch data to clinical reference tools. Researchers took factors like age, existing health conditions, device age, and activity into account.

And, as it turns out, the Apple Watch is, well, fairly accurate.

If you’re using yours to track your heart rate or step count, they’re quite accurate. The study found mean absolute percent errors, a standard measure of accuracy, of 4.43% for heart rate and 8.17% for step counts.

Energy, expenditure, on the other hand, was notably less accurate. The study showed that when it came to tracking calories burned, the Apple Watch was inaccurate nearly 28% of the time.

The energy expenditure inaccuracy was observed across all types of users and activities tested, including walking, running, cycling, and mixed-intensity workouts.

The Apple Watch remains a useful tool, not a diagnostic device

So you may be wondering if this means you should throw your Apple Watch into the trash. Obviously, it doesn’t.

University of Mississippi professor Minsoo Kang, who headed the study, still thinks these trackers have a place.

“These devices are great for keeping track of habits and staying motivated, but do not take every number as 100% truth, especially the calories,” he told Eureka Alert. “Think of it as a helpful guide, not a diagnostic tool. It is useful but not perfect.”

While they’re not perfect now, that doesn’t mean they’re not improving over time, either. Newer models of Apple Watch appear to be significantly more accurate than previous iterations.

“While we cannot say every update is a big leap forward, there is a noticeable trend of gradual improvements over time,” Doctoral student Ju-Pil Choe said. “It shows that Apple is refining the technology over time.”

Kang remains optimistic about the future of wearable tech. He hopes that the study can help users make informed decisions about purchasing wearable tech and that it could help inspire fitness tech creators to reexamine where devices fall short.

“By showing where the weaknesses are, we can help developers get real feedback,” he says “They know what needs to be fixed, they can design better sensors or algorithms.”

“Our findings can guide improvements and help make these devices more useful for both everyday users and health care providers.”

ZDNET’s key takeaways

• The Fitbit Charge 6 is normally priced at $160.
• This device helps minimize third-party distractions and notifications that other smartwatches may cause.
• Many forms of data are captured, like steps, sleep, and heart rate, to provide a comprehensive view of your daily activity. 

The Fitbit Charge 6 is currently on sale for $120 at Amazon. This deal applies to all three color options.

Smartwatches need to be charged at least every other day, and millions don’t want another device loaded with third-party apps and constant distractions on their wrist. The Fitbit Charge 6 offers a powerful wearable in a sleek form factor with a battery life that only requires a top-up once a week.

Also: The best smartwatches you can buy

With Google owning Fitbit, I see more Google integration in Fitbit devices. The Charge 6 includes support for playback controls of Google Music, Google Maps prompts on the tracker, and Google Wallet payment support. These features are provided in addition to the useful Fitbit functions, including detailed sleep tracking, EDA scans, Daily Readiness score, ECG measurements, step tracking, and an integrated GPS receiver for detailed outdoor tracking.

I wore a silver aluminum Fitbit Charge 6 with a porcelain band for a few weeks of testing, but the Charge 6 is also available in Black for $160. 

Looking at the hardware, Fitbit provides a lovely 26 x 21.8 mm AMOLED touchscreen color display. It is made with Corning Gorilla Glass, which looks superb and responds flawlessly to swipes and taps. The aluminum case surrounds the display and extends to the back heart rate sensor with nice curves and appealing aesthetics. The tracker is water resistant to 50m, so you can wear it 24/7 without worry.

The heart rate sensor on the back has greatly improved. Fitbit states that it is 60% more accurate during vigorous activities than older Fitbit devices. The sensor also supports ECG and EDA measurements to help detect heart rate irregularities and monitor stress.

Also: This midrange Android wearable outlasted my Galaxy Watch Ultra – and it’s on sale

The Fitbit Charge 6 also supports sharing your heart rate readings with some supported gym equipment, including treadmills, rowing machines, and bikes. Check out this Fitbit support site to see if this functionality supports your equipment. While the Fitbit Charge 6 is not listed on the official list, I tested it with my Hydrow rowing machine, which connected in seconds. With improved accuracy during activities and lots of movement, this is a nice capability if you don’t own an HR chest strap.

There’s a haptic button on the left side of the Charge 6. With this model, there is a designated target area to help you improve your accuracy in hitting it, and it is better than the no-button design that we saw on the Charge 5. I’m still more of a fan of a physical button, but I understand that for construction and water resistance, it is preferred to use a haptic button.

The Fitbit Charge 6 has an infinity silicone band, but there are plenty of other options, including sports bands, Horween leather bands, woven bands, hook/loop bands, and vegan leather bands, ranging from $30 to $50. Bands from the Charge 5 continue to work on the Charge 6, so if you want to upgrade after a couple of years, the Charge 6 is worth considering.

The software on the watch is easy to navigate, with swipes and taps providing access to key data and utilities. Google Maps works in combination with the app on your connected phone, so turns and other key information are presented on the Charge 6 while your phone remains in your pack. YouTube Music playback controls are supported for YouTube Premium subscribers, so you can store your phone away while exercising and still have control of your music.

Also: Finally, a budget smartwatch that’s just as durable as my Garmin (and it’s on sale)

Google Wallet works to support payments right from your wrist, but entering the PIN by scrolling up and down one digit at a time is a bit of a pain. Some work on making this easier is needed, or I will never use Google Wallet on the device.

Unlike a smartwatch and some past Fitbit devices, the Charge 6 does not have third-party apps available. However, Key Google, Fitbit, and basic clock utilities are provided on the watch and in the Fitbit app, so you can manage whether or not the apps appear on the Charge 6 as you navigate around the tracker. You can also customize nearly 30 watch faces.

The Charge 6 has an integrated GPS receiver, so you can run, walk, hike, and exercise outside without your phone. I tested this out for running and walking with an Apple Watch Ultra 2 on my other wrist and was very pleased with the accuracy of the GPS on the Charge 6. The Charge 6 supports GPS and GLONASS, while other watches typically support at least five global navigation satellite systems, so it will never be as accurate as dedicated GPS sports watches in challenging environments.

Also: Finally, I found an OLED sports watch that looks good and won’t break the bank

Google provides six months of free Fitbit Premium service with a Charge 6 purchase. Fitbit Premium is required for the Daily Readiness Score and other advanced features in the Fitbit application.

Compared to the Charge 5, I am very pleased to see the return of the floor’s climbed metric, improved heart rate sensor performance, side haptic button, and Google goodies (Wallet, Maps, and YouTube Music). The Charge 6 is also $20 less than the Charge 5’s launch price. The Fitbit Charge 6 is much better to sleep with than my larger smartwatches. Using the Charge 6 has me considering whether I need a full-size watch mounted on my wrist all the time.

ZDNET’s buying advice

While smartwatches are popular and often heavily promoted, having another device on your body that needs your attention may not be best for you and your mental health. 

Google offers the Fitbit Charge 6 as a device that captures key health and wellness data comfortably while minimizing the distractions of third-party apps and constant notifications. Sleeping with it on your wrist is very comfortable, and the data captured can be used to improve your health and lifestyle.