Sole ST90 Treadmill Review (2024)

The Sole ST90 is unique among the best treadmills on the market in that it can operate as both a motorized and a manual machine thanks to its rubber slat belt. This makes it especially useful for runners who want to alternate between endurance and interval training. While we haven’t had a chance to train on the ST90 ourselves, we have tested, owned, and sweat on more than 40 different treadmills, and after comparing the ST90’s features against previous Sole models and manual treadmills like the AssaultRunner Elite, we feel confident in offering our opinion in this Sole ST90 review. 

Running on an electric treadmill is much different than hitting the tread of a manual one, with each providing their own benefits and challenges, so we’re intrigued by the ST90’s hybrid design. However, this is an expensive profile, especially since it lacks some of the tech features of other treadmills in this price range. But if you’ve got the budget, we recommend it as a versatile, durable cardio machine that can bring some real variety to your at-home cardio routine. Keep reading as we dive deeper on the Sole ST90. 

Main Takeaways

• The Sole ST90 can operate as both a motorized and a manual treadmill, making it appealing to those who want to diversify their treadmill workouts.
• The individual rubber slats in the 20-inch by 60-inch belt may absorb more shock than traditional belt decks.
• Via the 15.6-inch touchscreen, runners can take Sole+ classes, access apps like Netflix, and mirror their own devices. 
• While the 2.0 Horsepower AC motor can provide more power than DC motors typically found in home treadmills, it can also be noticeably louder.

Sole ST90 Treadmill Highlights

• Price: $3,999
• Max Speed: 12mph
• Max Incline: 15%
• Weight Capacity: 400lbs
• Weight: 326lbs
• Roller Size: 7.44”
• Dimensions: 66” H x 82.5” L x 38” W

The Sole ST90 differs from other treadmills in that it eschews the hard, flat belts you’ll find on most electric units for a slat belt design that mirrors what you’ll find on a manual, non-motorized treadmill. In addition to providing more traction, the shock-absorbing rubber slats that make up this belt may put less impact on your joints than outdoor surfaces and flat belts. Because of its belt, the treadmill can provide both a motorized experience (great for endurance training) and a manual one (useful for interval training). 

It also has the heavy-duty steel build and weight capacity — 400 pounds — you’d expect in a machine that costs $4,000, which is between $500 and $2,500 more expensive than many of the best high-end treadmills. As Amanda Capritto, a certified personal trainer and CrossFit Level 1 trainer, pointed out when assessing the ST90 for BarBend, a 400-pound capacity is something you don’t see very often. “The industry standard for treadmills is a 300-pound weight capacity,” she said. “High-dollar models, including manual (non-motorized) treadmills, can have weight capacities up to 400 pounds.” 

We also like this machine’s 2.0 HP AC motor, which has the power to get you up to 12 miles per hour, even at a 15-percent incline. It would, however, be nice to see a decline range at this price point, especially since the motor has the power to support it. 

Most home treadmills rely on DC motors, while commercial treadmills designed to withstand heavy use often opt for AC motors. As such, you can expect this treadmill to withstand routine use for years to come, with proper maintenance, of course.  We should warn you, though, that AC motors tend to be louder than DC ones. 

Pros

• The rubber slat belt allows this machine to operate as both an electric and a manual treadmill. 
• The powerful 2.0 horsepower AC motor — often used in commercial treadmills — and supportive rubber slat belt make this tread ideal for endurance training.
• It can reach speeds up to 12 miles per hour and a 15-percent incline (8 percent when in Free Mode). 
• 10 programmed workouts, seven military fitness tests, and 12 streaming options come preloaded on the 15.6” touchscreen.

Cons

• The AC motor may be noisier than the DC motors you’ll find in many home treadmills. 
• It costs $4,000, between $500 and $2,500 more than most high-end treadmills. 
• At 326 pounds, it’s tough to move around, especially since it has no handles. 
• It has no folding or decline capabilities. 

Training With the Sole ST90 Treadmill

On its standard-belt treadmills, like the Sole F80 Treadmill and F63 Treadmill, Sole Fitness claims its Cushion Flex Whisper deck can reduce up to 40 percent of the impact on joints compared to asphalt. With the ST90, Sole continues in its efforts to provide a more comfortable cardio experience. 

Slat Belt

The ST90’s slat-belt design differs from the belts you’ve seen on most treadmills. Often, belts consist of either a single PVC rubber layer or a two-ply construction that layers on cotton, polyester, urethane, or mono-filament for added cushion. The belt is then wrapped around the rollers and supported by a flat deck. Slat belts, on the other hand, are built from individual rubber slats, connected horizontally — similar to the treads you might see on heavy vehicles like tanks or excavators.  

For athletes wanting the challenge of a manual treadmill, Sole ST90’s Free Mode answers the call. In this mode, the belt disengages from the motor and the user supplies all the juice to get the belt moving under their feet. 

Research has shown that running on a manual treadmill may help you burn more calories quicker than you would on an electric treadmill. It’s worth noting, though, that the ST90’s belt is flat, and these studies were conducted on curved treadmills. (1)(2) More research is needed to determine whether slat belts on flat, motorized treadmills can provide the same benefits as curved treadmills with the same belts, like increased oxygen uptake, heart rate, and calories expended. That said, the ST90 offers something the majority of curved treadmills don’t: incline capabilities.

Speed and Incline Ranges

The Sole ST90 can reach a 15-percent incline, which, at 326 pounds, is no small feat. In Free Mode — when the belt is powered manually — the incline tops out at 8 percent. In this mode, you may want to have gravity help get the belt moving by increasing the incline a few levels. On a curved treadmill, the downward slope of the front of the belt allows the user to leverage gravity to create momentum. Because the Sole ST90 has a flat design, increasing the incline can produce a similar effect.

Beside the sensors for heart rate monitoring on the handlebar, you’ll find the speed and incline adjustment knobs on the handrail. You can also use the quick-adjust buttons on the console to jump to specific settings. Sole provides similar functionality (and a 15-percent incline) on the F80, which our tester rated a 4 out of 5 in terms of adjustability. “It’s incredibly easy to switch up the levels of incline mid-run, which is useful during intervals,” our tester pointed out.

Display and Console

The 10 preset workouts, apps like Netflix and Disney+, and seven military fitness tests can be found on the 15.6-inch touchscreen display. After logging in, you can catch up on your favorite shows while following a HIIT or Fat Burn workout. On either side of the screen, quick-adjust incline and speed buttons are lined up vertically so you can easily jump to a specific setting.

[Related: The 8 Best Treadmills with Screens of 2024]

If your phone seems to always end up on the floor while you run, we have good news: the ST90 is packed with storage, from two bottle holders and a wireless charging pad below the display, to an integrated tablet holder above the screen. This is similar to the console on the F80. “In my experience, streaming music or workouts from my phone drained the battery pretty quickly, so I loved having the wireless charging pad,” said our tester, who rated the F80’s conveniences a 4.5 out of 5. 

You can also mirror the screen of your phone or tablet to the display via Bluetooth, which also allows audio to pump through the treadmill’s dual speakers. To adjust the volume, however, you’ll need to navigate the touchscreen, which may be annoying mid-run. Also on the console are two small fans and an emergency stop button with an attachable key. 

Dynamic Programming

With 10 workout programs built-in like Cardio, 5K Run, and Heart Rate, those looking for guidance and structure in a workout will be happy. However, Sole’s free companion app, Sole+ offers even more workouts — over 3,000 across their various machines. This same dynamic programming earned a 4.2 out of 5 rating from Kate Meier, certified personal trainer and BarBend editorial member, when she used the Sole F63. “I liked that I could customize my own program, as well as follow the standard, preloaded set,” she said.

Sole+ content can be accessed on your device or by mirroring your screen to the display. On it, you’ll find 1,400 treadmill workouts ranging from 10 to 60 minutes, with classes accommodating users of all fitness levels. 

[Related: iFit Review – Is Virtual Coaching The New Normal?]

Another convenient feature of the app is how it tracks your cardio metrics and preferences. Using your Sole+ profile, you can log in on both your device and the machine to sync your cardio workout history and stats like distance, calories burned, and heart rate. It will even remember your login for streaming apps like Netflix or ESPN, so you won’t need to type in your password every time you use the treadmill. 

What to Consider Before Buying the Sole ST90 Treadmill

With years of experience on over 40 treadmills, the fitness junkies on the BarBend team know what to look for in a quality treadmill. “There are many, many factors to consider when shopping for a treadmill,” said Amanda Capritto, a certified personal trainer and CrossFit Level 1 trainer. “They can be quite the investment, so it’s important to know what you’re getting.” Before you make the leap, make sure the price, type of belt, motor power, and footprint align with your intended use and available space. 

Price

The ST90 costs $3,999, which is high in the context of the $1,500 to $2,500 you’ll pay for most electric home treadmills. However, the ST90 is actually less expensive than other popular flat, motorized slat-belt treadmills, like the Peloton Tread+ ($5,995) or the Woodway 4Front ($13,995). The AssaultRunner Elite, one of the best curved treadmills on the market, runs for the same price as the ST90. 

Compared to the Sole F63 at $1,199 and F80 at $1,899, the ST90 costs more than double. Its hybrid design and high-end parts — like the AC motor and thick, rubber slat belt — are the primary reasons for the price difference. They’re great features for serious runners who see themselves sweating on the daily, but the casual athlete will likely find everything they need in a more standard option. 

That said, when compared to other flat, motorized slat-belt treadmills like the Peloton Tread, it is the cheaper option by roughly $2,000. But $3,999 is still $3,999, so be sure you consider how a purchase that large will impact your finances.

Slat Belt vs. Standard Belt

If you have used a treadmill in your life, odds are it was a standard belt. One piece of fabric is stretched around rollers and a flat deck, then powered by a motor. The decks under these machines are often cushioned to reduce the impact on your joints.

[Related: The 10 Best Cushioned Treadmills for 2024]

While there is some debate over whether slat belts on flat, motorized treadmills provide more shock absorption than standard belts, they definitely help absorb shock. With each footfall, the individual slats in the belt work to cushion each step, which disperses the force, and provides — at least according to some users — a gentler landing. There is still a need for more research in this area to establish whether more impact is absorbed by this type of belt.

AC Motor vs DC Motor

AC — alternating current — motors are typically found in commercial treadmills that rack up a lot of miles. Machines in gyms or fitness centers are used far more often than home treadmills with DC — direct current — motors, so they need heftier builds and motors to withstand that amount of use. Generally speaking, AC motors produce more power than DC motors, which also means they will also be louder. This may not be a concern in a busy gym full of people, but against a shared wall or near a sleeping baby, it could prove a distraction.

Bigger treadmills with higher overall weights and heavier frames are more likely to need an AC motor than the under-desk treadmill you use during Zoom calls. Moving a heavy-tread belt at a top speed of 12 miles per hour at a 15-percent incline just requires more power.

Footprint and Foldability

The Sole ST90 has a footprint of 21.77 square feet, which is roughly 5 square feet larger than your average two-seat sofa. (3) As such, this treadmill isn’t particularly suited to small spaces. It also doesn’t fold upright or flat, which is true of the comparable Peloton Tread+ and Woodway 4Front as well. 

“Check the overall length, width, and height of the machine in its assembled position and folded position if applicable,” Amanda Capritto, a certified personal trainer and CrossFit Level 1 trainer, cautions. “And triple-measure your space to make sure it will fit.”

The ST90 and the Sole F80 Treadmill have the same dimensions — 66” H x 82.5” L x 38” W — but the F80 is a folding treadmill. The difference is the type of belt they use. Slat belt treadmills require larger rollers than those with standard belts and this is true of the F80 and ST90. With a diameter over 5 inches larger — 7.44 inches compared to 2.36 inches — the Sole ST90 will not have the same maneuverability as the F80.

Sole ST90 Treadmill Vs. The Competition

Here are a few other slat-belt motorized treadmills. When making a purchase this large, comparing other similar options can provide valuable context to ensure you get the most bang for your buck. It’s also important to see features and specs listed beside other treadmills. This can help you make sure your treadmill has everything you need.

When placed side-by-side, it’s hard to tell where these slat-belt flat, motorized treadmills differ drastically. Each is operable as both a motorized treadmill and a manual treadmill. Woodway is considered by some to be the gold standard among slat-belt treadmills and has become something of a status symbol in fitness circles. It’s certainly the oldest company in the space — originally founded in Germany in 1974 — but Peloton and Sole also have put out comparable machines. 

All three have almost identical features — max incline of 15 percent and top speed of around 12 miles per hour — but where they differ is the display and accompanying technology. Peloton is well-known for its programming featuring engaging live and on-demand classes, so it follows that the Tread+ would feature a large, high-quality screen to show those classes. On the ST90, you’ll find the same display as the Sole F85: a 15.6-inch HD touchscreen. 

Woodway’s reputation for being pioneers in this space has made it something of a legend among athletes. According to GQ, every NFL, NBA, and MLB team uses Woodway machines, as well as Olympic athletes and even celebrities like Justin Timberlake. (4) It may be the gold standard among slat-belt treadmills, but you’ll need to decide how much that is worth to you.

Places to Buy the Sole ST90 Treadmill

You can buy the Sole ST90 Treadmill directly from the Sole Fitness website.

Warranties

Sole Fitness provides a 5-year warranty on the frame and motor; a 3-year warranty on the deck and parts; and a 1-year warranty on wear items and labor.

Customer Experience

Sole Fitness provides free shipping on all orders, financing is available with Shop Pay, and there are three delivery options: Curbside Delivery for free, Room of Choice for $199, and Room of Choice with Assembly for $350.

Company Information

Sole is known for its extensive line of cardio and home gym fitness equipment like treadmills, ellipticals, exercise bikes, and rowers. Its products are for both commercial and home use. Your purchase makes you eligible for a 30-day money-back guarantee if you aren’t satisfied with your treadmill. You can reach the company’s support team at 877-441-8433 or contact customer service representatives at: [email protected]

In Conclusion

Sole Fitness’ first flat, motorized slat-belt treadmill stands out for its ability to serve as both an electric and a manual treadmill. The commercial-grade 2.0 HP AC motor can reach 12 miles per hour, while the incline ability works during motorized runs (up to 15 percent) and manual ones (up to 8 percent), which allows you to add tons of variety to your home cardio workouts. 

While you may enjoy the power and stability the AC motor provides, it may be too noisy for users in shared or small spaces. It also may not be the best option for casual users. While $3,999 is less expensive than other similar hybrid treadmills that offer motorized and manual modes, we think the Sole ST90 is best suited for serious runners and athletes who want to diversify their training or a manual treadmill with incline. In that case, its technology features, steel frame, and (relatively) affordable price make the Sole ST90 worth a look.

FAQs

References

1. Robertson, Nicholas, “Comparing Calorie Expenditure and Rating of Perceived Exertion between the Curve and a Motorized Treadmill” (2014). EWU Masters Thesis Collection. 268.
2. Morrow, N., Weighart, H., Alonzo, D., Mitchell, K., & Ives, S. J. (2022). Physiological Responses to Speed-Matched Running on Non-Motorized Assault AirRunner versus Traditional Treadmills in Active Females: A Pilot Study. International journal of exercise science, 15(4), 1262–1273.
3. Jaramillo, C. (2022, December 29). A guide to sofa dimensions & sizes. SeatUp, LLC. https://seatup.com/blog/guide-to-sofa-dimensions/ 
4. Bradley, B. (2022, October 11). How this $14,000 Treadmill became the Ultimate Gym status symbol. GQ. https://www.gq.com/story/inside-the-cult-of-the-woodway

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