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Transform Your Strength Training Routine With Dynamic Weight Modes

Tonal’s digital weights let you challenge yourself in new ways with just the tap of a button.

Woman working out on Tonal.
  • Tonal’s dynamic weight modes give you variable resistance training with the touch of a button. 
  • Variable resistance training is a strength training technique in which weight changes within each rep.
  • Variable resistance training can help you build strength faster by challenging you to break through plateaus.
  • Tonal’s dynamic weight modes — Spotter, Smart Flex, Eccentric, Chains, and Burnout—make it possible for you to strength train in a way that can’t be duplicated with dumbbells.

Unlike dumbbells and gym equipment, Tonal’s digital weight adjusts thousands of times per second, making it possible to strength train in an unparalleled way. By automatically changing the resistance during a rep, or between reps in a set, Tonal ensures you’re getting the most out of each exercise. 

These variable resistance training techniques help you increase strength gains and break through plateaus. Learn more about how Tonal’s dynamic weight modes can help you get stronger, faster.

What Are Dynamic Weight Modes?

Dynamic weight modes are Tonal’s digital take on variable resistance training. They help you get stronger and improve body composition in different ways. You can do variable resistance training in the gym by changing the momentum, angle, or tension. However, this often requires additional equipment and an extra set of hands. 

How to Turn On Dynamic Weight Modes

Dynamic weight modes are automatically programmed into many Tonal workouts, but you can also activate them through the digital weight dial on your screen. With one tap, you’re able to access sophisticated weight lifting techniques without any specialized equipment or help from other people. Because Tonal senses your power and range of motion in each rep, the dynamic weight modes are customized to your own unique strengths and weaknesses in any given move.

How to Use Dynamic Weight Modes in Custom Workouts

When creating a Custom Workout on the Tonal app, you can choose a dynamic weight mode for a specific exercise on the movement page. Once you’ve selected a movement, you’ll see the weight mode options under the Sets & Reps section on the screen. 

Tonal has five dynamic weight modes: Spotter, Smart Flex, Eccentric, Chains, and Burnout. 


Spotter Mode: Automatically senses when you're struggling to complete a rep and temporarily reduces the weight so you can finish the set.

To keep getting stronger, you need to continually challenge your muscles by increasing the amount of weight you lift. If you’re working out alone, though, lifting heavy weights may be intimidating and potentially increase your risk of injury if you unexpectedly fail during a rep. 

Like a training partner at the gym, Tonal’s Spotter mode automatically senses if you’re struggling to complete a rep and temporarily reduces the weight so you can finish the set. If you’re able to continue the set at your original speed, Spotter will add the weight back for the remaining reps. This makes it easier and safer to confidently push your limits and hit new PRs. 

Spotter is always on by default, and you can use it for more than 200 moves to feel supported every time you lift. 

Read more about Spotter mode.

Smart Flex

Smart Flex: Automatically loads the strongest phase of any exercise and seamlessly removes it during the weakest phase of every rep.

When training with dumbbells and traditional static weights, the amount of resistance you can lift for each move is limited by your strength at the weakest point of an exercise. Leveling up the weight too soon may compromise your form at those weak spots, but sticking with a lower weight won’t challenge your muscles where they’re strong. 

To ensure you’re training at your full capacity through every millimeter of each rep, Smart Flex adjusts the resistance in real-time, adapting to your abilities. As you lift, Tonal calculates your strength curve, or points of difficulty in a movement, and Smart Flex intelligently matches your strength by continuously adding or subtracting weight at the appropriate point in the curve. 

When Smart Flex is activated, it will kick in on the second or third rep of your set, once Tonal senses your range of motion and strength curve for an exercise. As a result, you’re lifting more weight, pushing your muscles harder, and getting stronger.

Read more about Smart Flex mode.


Eccentric Mode: Automatically loads the eccentric phase of any exercise and seamlessly removes it during the concentric phase during every rep.

Every lift has two phases: concentric and eccentric. For example, a biceps curl consists of a concentric portion when you lift the weight and an eccentric portion when you lower the weight back down.

With traditional weights, the concentric phase is usually more challenging as you’re fighting against the forces of both weight and gravity. But adding load to the eccentric phase, when the muscle is elongated, offers additional benefits such as improvements in flexibility and range of motion, lower injury risk as you become more efficient at braking, and increased strength in everyday activities that require both concentric and eccentric movement. 

In the past, changing weight between phases wasn’t possible without a team loading and unloading a barbell as you lift. With digital weight, you can do it on your own, automatically and seamlessly with the click of a button. With Eccentric mode, Tonal adjusts weight in the eccentric phase to be 25 percent heavier than your concentric load without hitting your max weight, which is consistent with research-backed recommendations

You can add up to 60 percent of the weight to optimize your time under tension, building muscle and increasing your strength faster. 

Read more about Eccentric mode.


Chains Mode: Mimics the sensation of actual chains being lifted off the floor by getting heavier as you lift and lighter as you bring the weight back down.

Have you ever seen a person at the gym doing barbell curls with massive chains hanging off the ends? The idea behind loading up a barbell with extra metal is to increase resistance in the concentric phase of a move, the opposite of Eccentric mode. Adding load in the concentric portion of an exercise improves your max strength, primes your nervous system for heavier lifting, and prevents overtraining when you’re also doing eccentric lifting. 

Adding chains is not so easy in the gym — it requires additional bulky and noisy equipment. With Tonal, it’s straightforward and requires no additional equipment. Chains mode simulates the feeling of real chains at the touch of a single button. Additionally, Chains mode on Tonal isn’t limited by gravity and can be used in any plane of motion, including horizontal and rotational exercises. This dynamic weight mode increases the intensity of any move to help build explosive power.

Read more about Chains mode.


Burnout Mode: Automatically reduce the digital weight when you're struggling, but the goal is to keep repping it out until the set is over.

Drop sets—in which you gradually reduce the weight as you fatigue in a high-rep set without stopping until you reach failure—are scientifically proven to stimulate muscle growth by increasing volume in your workouts without extra rest periods. 

Performing a set like this with dumbbells or traditional weights requires you to swap weights between reps, using lighter dumbbells every time. Tonal’s Burnout makes it possible for you to perform drop sets without any additional equipment. This dynamic weight mode senses when you’re slowing down and reduces resistance in a high-rep set so you can complete your last rep successfully and keep pushing yourself to build muscle. It’s most effective in sets of 15-20 reps or timed sets when you’re trying to squeeze in as many reps as possible.  

Read more about Burnout mode.

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