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Product News Introducing Smart Flex: A Revolution in Strength Training

A man completes an exercise, on-screen animation shows weight changing automatically.
  • Discover a new way to strength train with our patent-pending Smart Flex.
  • Tonal’s dynamic weight modes — Spotter, Burnout, Chains, and Eccentric —  make it possible for you to train in a way that hasn’t been possible before. Our revolutionary Smart Flex takes it to another level. 
  • Smart Flex helps you get stronger faster by making it possible to lift in a way that isn’t possible with dumbbells or traditional weights.
  • Smart Flex dynamically adjusts the weight, down to the millisecond, for the most effective rep every time — a completely new technique in variable resistance training.

Tonal’s patent-pending Smart Flex technology will change strength training forever. When training with dumbbells and traditional static weights, the amount of resistance you can lift for each move is limited by the points where your muscles are weakest. Dumbbells and traditional static weights will never know where your body is naturally stronger in a rep, but Tonal does. That’s why training with digital weight and Tonal’s A.I. can get you better results, faster. 

Smart Flex utilizes Tonal’s digital weight system to deliver resistance with precision, down to every millimeter, of every rep. Depending on when your muscles are their strongest during a move, Smart Flex intelligently matches your strength by continuously adding or subtracting weight. This ensures that your muscles are optimally challenged throughout the entire range of motion of a rep. As a result, you’re lifting more weight, pushing your muscles harder, and getting stronger, faster.


Smart Flex is Tonal’s newest take on variable resistance training. Strength training enthusiasts are constantly trying to find new ways to make each rep more challenging. In the gym, this can be done by changing the momentum, angle, or tension at the beginning or end of a move or by adapting it — preacher curls instead of bicep curls — to using bands or chains. 

Doing this manually often requires a lot of guesswork and tools, not to mention that each move has a different strength curve. Smart Flex calculates the strength curve of every movement, and Tonal can adjust digital weight based on this to give you more volume and optimal resistance with every rep. 


A graph shows changing lines and data. A dial shows increasing and decreasing numbers.

Strength curves refer to the difficulty of a move throughout its range of motion — points where your muscles will feel weaker, and points where they will feel stronger. When training with dumbbells and traditional static weights, it’s not possible to increase the amount of resistance you can lift for the points where your muscles are strongest. 

Smart Flex sets the standard by dynamically adjusting digital weight every millisecond, over every millimeter, for the entire range of motion of a rep.

Tonal’s A.I. analyzes each of the moves in our library to determine the strength curve for every muscle involved, and adjusts the weight to reflect those unique differences. Digital weight bypasses gravity, inertia, and momentum, adjusting specifically to the way your body moves. The results transform every rep to your most efficient one, every single time. 

Here are some examples of where your body would be strongest in a move according to its strength curve:

Strongest at the top

When doing deadlifts, you pull a lot of weight off the ground, which is the hardest part of the move. Therefore, Smart Flex increases weight at the top of the move, when your body is strongest.  

Stronger in the middle

For moves like bicep curls and its variations like hammer curls, the movement is harder at the beginning and end but easy in the middle. Therefore, Smart Flex will increase the weight mid-rep.

Strongest at the bottom

Barbell rows are surprisingly not too bad until you start pulling up to your stomach — that’s when it can get tough! Smart Flex adds weight at the bottom of the move and decreases as you pull up.

Strong the whole time 

Cable flyes are an example of a move where the relative difficulty is roughly constant throughout the whole range of a move. In this instance, Smart Flex will only add resistance as you pull the weight back.  


Tonal has revolutionized strength training by offering the most precise control available in resistance weight, Smart Flex adds another dimension to getting stronger, faster with Tonal’s digital weight. Smart Flex joins our other dynamic weight modes like Spotter, Burnout, Chains, and Eccentric — all of which allow you to lift and break through plateaus like never before.


Chains and Eccentric modes follow patterns that mimic the advanced methods one could do in the gym with specialized equipment. Chains will add weight when the cable is extended with a push or pull (when your muscles contract), and Eccentric adds weight as you retract the cable (when your muscles lengthen). 

In contrast, Smart Flex maps out the easiest and most challenging moments of a specific move, and precisely adjusts weight throughout the entire range of motion. Combining the best elements of both Chains and Eccentric, Smart Flex optimizes every rep to be as challenging as possible.


Smart Flex appears as an option in your weight dial, much like Chains and Eccentric modes. Swipe your weight dial to the left during a workout to see the options and then tap on Smart Flex to enable it for the move. Smart Flex will set the base weight at the optimal amount and kick in on the second rep, so you hit your max weight at your strongest points in a movement. 

Try a workout or program that uses  Smart Flex. Keep an eye out for these two options coming to your trainer today:

  • Smart Flex Blast: Single workout with Coach Nicolette
  • Smart Flex Challenge: 3-Day Program with Coach Nicolette

Tonal is revolutionizing strength training with digital weight, expert coaching, and progress tracking. Smart Flex takes it to the next level, challenging your body in a way that cannot be replicated with traditional weights and dumbbells. Tonal will continue to push boundaries and explore new ways to make you stronger than ever before, and Smart Flex brings you another step closer.