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Want to Build Muscle and Boost Power? Try Variable Resistance Training

Variable resistance training takes your workouts to the next level by changing the demands on your muscles within each exercise.

Coach Joe Rodonis on Tonal using variable resistance
Coach Joe Rodonis doing a bench press on Tonal, which allows you to easily activate variable resistance.

To get stronger, you have to lift more. That’s pretty much the guiding tenet of strength training, a.k.a. the principle of progressive overload. Making gains requires increasing the weight, frequency, or number of repetitions in your workouts. 

There’s a catch, though: When it comes to adding more load to an exercise, you’re only as strong as your weakest point in that movement. But if you can get your muscles to work harder where they’re the strongest without compromising those weaker points, you can get stronger overall. That’s where variable resistance training can be effective.  

What Is Variable Resistance Training? 

When you use a free weight like a dumbbell, that’s constant resistance—meaning the amount of resistance against your muscles doesn’t change no matter what phase of a movement you’re in. 

On the flip side, “variable resistance training is when the weight that you’re using changes throughout the range of motion of an exercise,” says Tonal coach and certified personal trainer Joe Rodonis.

Take a bench press, for example. When you do a bench press with a barbell or dumbbells, the weight is constant, whether the bar is lowered to your chest or your arms are locked out at the top of the movement. Eventually, with constant resistance, you’re going to hit a point where you can’t increase the weight without reducing your range of motion or failing to complete the rep. Add too much weight to the bar for that bench press, and you may not be able to lower it with control.

That’s where variable resistance comes into play. Adding equipment like resistance bands or chains to an exercise leads to “different demands on your muscles throughout that range of motion,” says Rodonis. 

Let’s go back to that bench press: If you add chains to each side of the barbell, the resistance would lower as you lower the bar towards your chest, because the weight of the chains collects on the floor. But as you press the bar back up, you have to generate more force than normal to get those chains off the floor and reach the top of the lift. (A resistance band would have a similar effect; the further you stretch the band, the more resistance you have to work against.)

“Strength training is mass times acceleration,” says Rodonis—so the limiting factor with constant resistance is that as resistance increases, the speed of a movement gradually decreases. The result: a “sticking region” at the weakest position of the joint, which inhibits your progress. With variable resistance, however, the goal is to create more resistance where your muscles produce the most power. 

What Are the Benefits of Variable Resistance Training?

As your strength increases, it’s harder to make gains (at the very least, they’re less noticeable). So the biggest payoff that comes with variable resistance training is the fact that it helps you avoid any plateaus, says Rodonis. When your body acclimates to a certain weight but you’re not necessarily ready to increase the constant resistance, adding variable resistance can increase demand without overloading your body. In fact, variable resistance delivered significantly more strength gains than just lifting weights, research published in The Journal of Strength and Conditioning Research found.

Training with variable resistance also improves your power—or how quickly you can move under load. Athletes who added variable resistance (in the form of bands) to one lifting session per week over the course of five weeks of training showed a higher rate of power development than those who didn’t use bands in a 2016 study published in The Journal of Strength and Conditioning Research. Power training targets the fast-twitch muscle fibers—the main ones used during explosive movements like sprinting and jumping—which can make variable resistance great for sport-specific training.

Plus, variable resistance training can be a safer and more sustainable way to make gains, because it reduces the load on your joints at their most vulnerable position, says Rodonis. Using variable resistance (in this case, chains) was shown to reduce shoulder pain during bench pressing in a 2019 study published in the Journal of Physical Education and Sport.

How to Incorporate Variable Resistance Training at Home

With all the talk of chains and such, variable resistance training might sound daunting. But Tonal takes the intimidation out of it. Instead of actual chains and bands, you can use dynamic weight modes to vary the amount of resistance during a given exercise with just a couple taps on your Tonal screen. If you’re doing a coach-led workout or program, dynamic weight modes are already programmed in for you, so you can just focus on exercising. 

Dynamic weight modes; variable resistance training on Tonal

For starters, there’s Chains Mode, sans any noisy, heavy metal. This adds load to the concentric portion of an exercise—when a muscle shortens—to improve your max strength. And, unlike in the real world, you aren’t limited to vertical exercises; with Tonal, this method of variable resistance can be used in any plane of motion, including horizontal and rotational exercises.

In Smart Flex mode, Tonal’s advanced AI will determine any points of difficulty you’re having in a movement, and intelligently match your strength by continuously adding or subtracting weight at the appropriate points (it kicks in on the third rep of a set). 

“That allows you to continue to work on your strengths while breaking through those sticking points for a more efficient rep,” says Rodonis. More efficient reps equal bigger gains over time.

Eccentric Mode is another way to incorporate variable resistance training. With constant resistance, the concentric phase of an exercise is usually more challenging because you’re working against the forces of both weight and gravity. But focusing on the eccentric phase—when a muscle lengthens—can make a move more challenging. And studies show eccentric training is incredibly effective for building muscle and boosting performance. 

“It’s like loading up a spring,” says Rodonis. “Picture a lunge: As you step back, the weight is going to increase. To push back up to stand, you have to generate more force at a higher rate.” Not only does that lead to strength increases, it improves your flexibility and range of motion, all of which can help reduce the risk of injury. 

No matter what your end goal is, variable resistance training is an easy way to take your training to the next level.

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