The Core Exercise Trainers Love (No, It’s Not A Plank)

We’re not here to play games: The truth is, there’s no magical workout move that does it all. However, there are certain exercises that set you up to move better and lift things more easily. Many of these involve strengthening your core, because a strong midsection is essential for every workout, sport, and fitness activity — not to mention daily life. And that’s where the core reach (also known as the dead-bug exercise) comes in.
This move — think of it as a flipped-over version of a moving plank — is functional, safe, and strengthens the same muscles you use for everything from doing squats to hauling groceries. It’s also especially useful for runners because it teaches trunk stability and control while you’re moving your arms and legs in opposition. This mirrors what you do when you’re walking and running, explains Ashleigh Kast, trainer at Drive Clubs in New York City and founder of Sophisticated Strength. This stability helps establish a more efficient stride pattern that controls breathing and prevents lower back pain often caused by poor running form.
You can include the core reach as part of your warm-up before a gym workout or run, or try it as a quick exercise first thing in the morning. Plus, it’s simple to increase or decrease the intensity level depending on where you are in your fitness journey. Just lace up a pair of supportive and cushiony adidas UltraBOOST X sneakers and follow along with brand ambassador Jera Foster-Fell. Time to kick-start your workout.
The Core Reach
Start lying on your back with arms extended straight in the air with wrists over shoulders. Bend your knees to a tabletop position, making 90-degree angles with your shins parallel to the floor. While pushing your low back against the ground, extend your right arm overhead and your left leg outward until they hover a few inches off the floor, but not so low that your back arches. Immediately return to the starting position, and repeat on the opposite side. Do 10 reps on each side, alternating arms and legs each rep.
“The most common mistake I see people make is beginning with the back arched,” Kast says. Fix this by flattening your back on the floor before you start moving, and be conscious to maintain that position throughout the entire exercise.
“This move is an amazing opportunity to begin linking your breath to your movement, which is key for mastering any exercise or sport,” says Kast. Inhale as you lower your arm and leg and exhale as you pull them back in.
Just Getting Started? Try This Beginner-Friendly Variation
Keep your arms extended by your sides on the ground or directly overhead. Bring your legs into that same tabletop position and — keeping your knees bent at 90 degrees — lower your right heel to tap the ground. Return your leg to the starting position, and repeat with your left leg. By shortening the length of your legs, you reduce the load on your core, thus requiring less stability, and you’re using your arms to help you balance. Do 10 reps on each side, alternating legs each rep.
For More Of A Challenge, Add Some Weight
While holding a five- to 10-pound medicine ball (a kettlebell or single dumbbell does the job, too), extend your arms directly above your head and perpendicular to the floor. Keep your arms in place while extending one leg at a time. The goal here is to create maximum tension in the body, so imagine you’re trying to crush the ball between your hands. This tension helps stabilize your core and adds work for your upper-body muscles. Do 10 reps on each side, alternating legs each rep.

Mass Fidelity Core and Core Sub review: Exceptional Bluetooth speakers

Mass Fidelity Core

  • Mass Fidelity Core Wireless Speaker System


    $499.00 MSRP $599.00


    on Amazon
  • Mass Fidelity Core Sub Wireless Subwoofer


    $299.00 MSRP $299.00


    on Mass Fidelity
I first wrote about Mass Fidelity’s Core Bluetooth speaker way back when it was the subject of a highly successful crowdfunding campaign. That campaign raised so much cash that Mass Fidelity quickly put a companion subwoofer on the development fast track. Both speakers have been available for a while, so my reviews of both products are ridiculously overdue.

The good news is that Mass Fidelity delivered on every promise it made for each product. The Core itself produces sound that’s completely out of proportion to its size. Just six inches square and four inches high, the Cube easily filled my 247-square-foot home theater with sound.

The Core’s 120-watt amplifier and five drivers (two full-range speakers in front, one on each side, and a down-firing woofer at the bottom of the chassis) don’t produce the conventional stereo image that restricts the listener to a single sweet spot to enjoy the best experience.

The bad news is the Core’s $599 price tag. Ouch. At the time of this writing, Mass Fidelity was running a promotion that knocks $100 off that bill, but it’s slated to expire August 6.

  • Acoustic holography
  • Bluetooth and I/O ports
  • The Core Sub
  • Multi-room and networking capabilities
  • Worthy or not?

Acoustic holography

Outfitted with six digital signal processors and an ARM-based CPU, the Core uses an audio rendering technique called wave field synthesis to create a virtual acoustic environment in which the sounds in a recording remain in position no matter where the listener is located in the room (Mass Fidelity calls it “acoustic holography”). In other words, if the drums in your favorite recording were engineered to emerge largely from the left speaker, and the vocals predominantly from the right, that’s how you as the listener will perceive them, no matter how far off axis you might be in relation to the Core’s center. It’s not perfect—true wave field synthesis relies on much larger speaker arrays—but it is quite remarkable.

Traditional Sweet Spot vs. Sonic HolographyMass Fidelity
Mass Fidelity’s somewhat tongue-in-cheek illustration of its “sonic holography” compared to a conventional stereo sweet spot.

Whether I was listening to Pink Floyd’s “Breathe in the Air” (Dark Side of the Moon), Donald Fagen’s cover of “Ruby” (The Nightfly), or Bruce Cockburn’s “Mango” (Breakfast in New Orleans, Dinner in Timbuktu), I could sit or stand anywhere in my home theater and perceive the same soundstage. And the Core’s audio performance knocked me out with crisp, clear highs; meaty mid-range; and fat bass.

In my 2014 preview of the Core, I wrote that the demo unit sounded better than any Sonos component. Sonos has since shipped its second-generation Play:5 speaker, and that is no longer the case. The new Play:5 is somewhat louder than the Core and it delivers more low-end. Adding a Core Sub to the Core erases that deficit, but it’ll cost you another $299. On the other hand, the Play:5 is significantly larger and is forever tied to an electrical outlet. The Core can run on either AC power or its built-in battery, which is rated to last 12 hours. I’ll go deeper into this comparison when I discuss the Core’s multi-room capabilities.

Bluetooth and I/O ports

Most people will use the Core as a Bluetooth speaker, but it can also work with other sources, including your TV if you want to use it like a sound bar. The Core’s rear panel has an 1/8-inch analog aux input, a Toslink digital input, and an 1/8-inch analog subwoofer output (Mass Fidelity’s own subwoofer is wireless). The speaker even has a built-in microphone, a feature that enables you to use it as a Bluetooth speakerphone.

Mass Fidelity Core I/O ports

Michael Brown

The Mass Fidelity Core can rebroadcast signals from its analog and digital inputs. The USB port is useful only for charging a smartphone or digital audio player.

An onboard DAC can handle PCM streams with up to 24-bit resolution and 192kHz sampling rates. And the Core can stream any of those sources—including Bluetooth—to Cores in other rooms in your home (more on that later). The Core comes with a rudimentary remote control, but it’s also outfitted with an infrared receiver port if you wanted to integrate it into your smart-home system.

The Core has a Bluetooth operating range of 10 meters (about 30 feet), but obstacles such as walls and appliances quickly reduce that range. My Samsung Galaxy S6 Active lost contact with the speaker when there were more than two walls between the two. If you’re streaming from your phone, you’ll probably want to leave it in the same room as the speaker. The Core supports the aptX, AAC, and SBC codecs, and Mass Fidelity encourages users to stream higher-resolution audio files such as FLAC, WAV, or Apple Lossless (AirPlay, by the way, is not supported). The tracks I tested were all ripped from CD and encoded as 16-bit/44.1kHz FLAC files.

The Core Sub

The Core delivers amazing bass response for a speaker its size. Most people will be completely satisfied with its performance on that score. Bass fiends—and anyone who wants to use the Core as a sound bar with their TV—will want to add the Core Sub to the mix. Well priced at $299, the sub adds extra oomph at the bottom end, and it frees up the Core’s DSPs to concentrate their computational horsepower on processing mid-range and higher frequencies. So you get more than just more boom in the room with the sub.

Mass Fidelity Core Sub

Michael Brown

The Core Sub can be oriented on its side (as shown here); horizontally, so you can slide it under your sofa; or vertically.

The Core Sub has an 1/8-inch analog input, but its connection to the Core is wireless; pairing the two takes just a couple of button presses. The sub can be operated horizontally, with its speaker firing down at the floor; vertically, bouncing its sound off the wall; or on its side if you add the additional footpads to its four corners. Buttons on the sub enable you to change the crossover frequency, gain, and phase.

The sub is a good value, and most people will appreciate its contribution to the Core’s audio performance. But I found that it didn’t like to be driven hard, turning flabby and flatulent if I cranked the volume too much. The Sonos Sub is far better, but it’s also much more expensive at $699.

Mass Fidelity Core Sub controls

Michael Brown

The Core Sub has phase and gain control along with an adjustable crossover.

Multi-room and networking capabilities

Mass Fidelity pitches the Core and Core Sub as a multi-room audio system, but that claim is a bit of a stretch. On the upside, the master speaker will broadcast the audio from any of its inputs to up to eight other Core speakers over its own proprietary 5GHz wireless network (each Core Sub counts as one of those eight units). On the downside, all the speakers must play the same music—you can’t control them independently from one Bluetooth device.

You can switch any Core speaker out of multi-room mode and stream music to it independently, but you’ll need to establish a Bluetooth connection to that one speaker and you won’t be able to control the others from that device. You can also set up four independent networks, each with up to eight devices—32 in all—but there’s no scenario in which you can stream one track to the kitchen, a different one to the bedroom, and a third to the garage from a single source. That’s a piece of cake with a Sonos system.

The fact that Mass Fidelity doesn’t have an app for its system is good and bad. On the good side, you can continue to rely on the apps you’re already familiar with. Spotify users can use Spotify, Tidal users can use Tidal, and so on. The output is simply streamed over Bluetooth and there’s nothing new to learn. If you prefer to stream from your own library, using a NAS box running a DLNA server, for instance, you can do that, too. I used BubbleUPnP on my Android phone to stream from my music collection that’s stored on aWD MyCloud Mirror NAS.

Mass Fidelity Core controls

Michael Brown

You can adjust the Core’s volume using buttons on top of its enclosure. The button on the far left enables multi-room mode, and the one next to it switches inputs.

On the bad side, the absence of an ethernet or Wi-Fi adapter on the Core means that everything must flow through your smart device—a smartphone, for most people. That will impact its battery life, and as I’ve already pointed out, you’ll feel obligated to leave that device in the same room as the speaker so you don’t risk breaking the Bluetooth connection. If you live in an apartment or a relatively small house, that probably won’t be a burden. If you live in a split-level, it could be aggravating. Sonos still carries the day when it comes to reasonably priced multi-room audio systems, even if it doesn’t have a small speaker that can touch the Core.

Worthy or not?

For all their faults, Mass Fidelity’s Core and Core Sub are remarkable speakers. The company’s acoustic holography isn’t just a marketing gimmick—it really works. In a world where few of us have rooms set up specifically for music listening, with a single chair dead center in the stereo sweet spot, this technology is absolutely fabulous.

Mass Fidelity Core remote

Michael Brown

The Core comes with a basic remote control. It can also be incorparated into a smart-home system via an infrared receiver port in back.

The Core delivers remarkable performance for a speaker its size, it can run with speakers several times larger, and you can carry it with you from one room to another thanks to its onboard battery. It’s also beautiful to look at. I’m only slightly less enamored with the Core Sub. It’s not the best subwoofer I’ve heard, but the combination of the two speakers is dynamite.

If you want a true multi-room system, stick with Sonos. It’s not Bluetooth compatible and it doesn’t boast fancy psychoacoustics like wave field synthesis, but you can buy less-expensive speakers for smaller rooms and its networking technology is far more sophisticated and flexible.

As a single-room speaker, I like the Core more than most every other Bluetooth speaker I’ve heard, including Naim Audio’s higher-priced Mu-so Qb. And if you can get over its limitations, the Core is probably the best Bluetooth multi-room speaker system out there (Sonos doesn’t offer native Bluetooth support).