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Advanced Methods

Eccentric Training and Overload

One of the most important advantages of flywheel training on the kBox is its ability to provide eccentrically overloaded training in a safe, practical and efficient way.



Your muscles are stronger in the lengthening (eccentric), the phase of its motion, as compared to the shortening (concentric), phase.

Training the eccentric phase has strong scientific support, the most important being increasing total strength and hypertrophy. As many injuries occur during eccentric contraction, eccentric training can also greatly reduce the risk of injury for elite athletes as well as rehabilitation clients. Eccentric training is also shown to transform muscle into a faster phenotype.

In regular strength training with weights, the load in the eccentric phase is limited to how much the weaker concentric phase can lift. As a result, the eccentric phase is rarely loaded to its maximum, and the training loses efficiency.

Training with focus on the eccentric phase is called eccentric or negative training.

Eccentric Overload

Eccentric overload is when the eccentric force is larger than the maximal concentric force.

To reach your maximal force in the eccentric phase, you need to apply some method to get eccentric overload.

In traditional strength training with weights, achieving eccentric overload is challenging from both a practical and a safety point of view. The traditionally applied methods include:

  • Help from training partners with lifting beyond your max in the concentric phase, as well as controlling yourmovement in the eccentric phase. These methods are often time-consuming and have a high risk of injury.
  • Using certain weights stack machines, for example, leg extension by using both legs up and only one leg down, which is not a very functional movement.
  • “Cheating” using auxiliary muscle in the concentric phase, but you often get less efficiency in the concentric phase and also increases the risk of injury.

The Flywheel Advantage

With flywheel training, eccentric training and heavy eccentric overload have never been easier or safer.

Using the kBox you can use our methods to perform eccentric training with overload without help and also without the risks associated with traditional methods.

If you decelerate the flywheel in a shorter time than the acceleration phase, you will produce a higher eccentric force. You can also produce force in the concentric phase with auxiliary muscle and only use certain muscles in the eccentric phase to overload them. Read more.

With the addition of the kMeter wireless feedback system, you can easily measure the eccentric power and overload.

Eccentric training is getting safer and less practically challenging as flywheel training gains momentum across the globe.

Mike Young discussing Flywheel Training during Athletik-Konferenz 2018 in Germany

Full video available here


kBox4 Active

Our entry level model for the serious personal trainer or demanding home user. The perfect tool in strength and rehabilitation at our lowest price point.

  • Entry Level Model
  • Holds 1-2 Flywheels
  • kMeter Compatible
  • Weighs 15 kg
  • Starting at €1 410 / $1 635
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kBox4 Lite

Offers the lowest weight and best portability which makes it perfect for frequent travel without compromising the training.

  • Enhanced Portability
  • Holds 1-4 Flywheels
  • Built in kMeter
  • Weighs 9.5 kg
  • Starting at €2 300 / $2 665
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kBox4 Pro

Our premium kBox model with the greatest versatility and largest performance area. It’s ideal for sports teams, premium fitness clubs and physiotherapy facilities.

  • Largest Performance Area
  • Holds 1-4 Flywheels
  • Built in kMeter
  • Weighs 15.5 kg
  • Starting at €2 990 / $3 465
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The kPulley2 is the ideal horizontal solution for improving strength by offering flywheel training for rotational and pull exercises.

  • Horizontal Model
  • Holds 1-2 Flywheels
  • Built in kMeter
  • Easy to assemble
  • Starting at €1 890 / $2 190
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