Inertia in Flywheel Training

Understanding the concept of inertia is key to reaping the benefits of flywheel training. Instead of using weights, the resistance in flywheel training is created through the inertia of a flywheel which is rotated with muscle force.

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Gravity vs Inertia

Traditional strength training is generally done by lifting some sort of weight – such as a barbell, dumbbell and weight stack machines – against gravity to create resistance.

In flywheel training or isoinertial training, resistance is created through the inertia of a flywheel, which is accelerated or decelerated with muscle force. The level of inertia of the flywheel rather than the weight determines the force needed. The principle is equivalent to that of a traditional yoyo device.

The resulting force in a flywheel training exercise depends on a combination of the inertia and the intensity you work with. With a higher inertia, the motion will be slower and more controlled, and your muscle will be able to produce a higher force. With a lower inertia, the motion will be faster which also puts higher demands on skill, balance and technique.

Inertia on the kBox, kPulley and SingleExx

Our kBox, kPulley and SingleExx devices can be equipped with two or four flywheels simultaneously depending on the device model. Additionally the Advanced Flywheel Knob can help to boost that capacity by two flywheels of a compatible size. Our flywheels come in five different sizes with inertia ranging from 0.005 kgm² to 0.070 kgm².

  • Extra Large: 0.070 kgm² (only compatible with the kBox Pro, LegExx, LegFlexx and all kPulley devices)
  • Large: 0.050 kgm²
  • Medium: 0.025 kgm²
  • Small: 0.010 kgm²
  • Extra Small: 0.005 kgm²

Choosing Inertia

In flywheel training, choosing inertia means more than deciding between light and heavy. The inertia resulting from the size and number of flywheels impacts the training adaption you get.

Together with your workout intensity, the the ideal choice of inertia depends on your exercise purpose, also coined the Flywheel Workout Zones.

 
 
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Active

kBox Active

Kickstart your Flywheel Training with our entry-level kBox model. The perfect device for strength training, rehabilitation, injury prevention, and training in general. Available with our free Exxentric app to help guide you through your workouts.

From: $ 1,620

  • Ideal for...
  • • Home Gyms
  • • Personal Trainers
  • • Group Classes
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Lite

kBox Lite

The lightest kBox model, practical to pack and bring with you on the go. It not only offers a broader range of resistance compared to the Active model but its built-in kMeter feedback system also allows you to monitor your progress in real-time.

From: $ 2,610

  • Ideal for...
  • • Travelling Athletes
  • • Fitness Studios
  • • Physiotherapy Rooms
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Pro

kBox Pro

The premium and best-selling kBox model with the largest performance area. Made for intense workouts and serious strength building exercises. Its built-in kMeter feedback system allows you to monitor your progress in real-time.

From: $ 3,510

  • Ideal for...
  • • Professional Teams
  • • Performance Centers
  • • Physiotherapy Clinics
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Legacy

kBox Legacy

Shortly after its initial launch in 2016, the kBox4 product line has been boosted by the kBox4 Active. And now with the launch of our user-inspired fifth generation of kBoxes we’re excited to offer better deals on the Legacy line until stocks last.

From: $ 1,420

  • Ideal for...
  • • Home Gyms
  • • Travelling Athletes
  • • Professional Teams
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Pro

kPulley Pro

The kPulley unlocks a variety of horizontal movements, creating limitless training possibilities especially when combined with the kBox. Its built-in kMeter feedback system allows you to monitor your progress in real-time.

From: $ 2,520

  • Ideal for...
  • • Professional Teams
  • • Performance Centers
  • • Physiotherapy Clinics
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Go

kPulley Go

Kickstart or enhance your Flywheel Training setup with one of our entry-level models. Its compact size and design provides you with freedom in your training, while also maintaining a great capacity for loading & variable resistance.

From: $ 1,320

  • Ideal for...
  • • Home Gyms
  • • Group Classes
  • • Physiotherapy Rooms
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SingleExx

These uniquely mobile machines allow you to incorporate leg extension & flexion movements into your training like never before with variable & unlimited resistance. Progress can be monitored in real-time and beyond through the Exxentric app.

From: $ 6,100

  • Ideal for...
  • • Professional Teams
  • • Health Clubs
  • • Physiotherapy Clinics
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